Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0071763 nuclear membrane organization	IBA GO_REF:0000033	ACCEPT	Summary: Nuclear membrane organization - core function. LEMD2/LEM2 closes nuclear envelope holes around spindle microtubules together with CHMP7, and its C-terminal winged-helix domain copolymerizes with CHMP7 into 50-100 nm rings that restrict diffusion at NE holes. Reason: Primary process supported by multiple mechanistic studies. Supporting Evidence: file:human/LEMD2/LEMD2-deep-research-perplexity-lite.md See deep research file for comprehensive analysis file:human/LEMD2/LEMD2-deep-research-falcon.md LEMD2 is described as a ubiquitously expressed INM protein with a conserved N-terminal LEM domain and two transmembrane segments, localizing at the nuclear periphery. Its LEM domain enables association with DNA-associated proteins including lamins and BAF, supporting a chromatin–nuclear envelope tethering function. PMID:37795681 The LEM-domain protein LEMD2 contributes to NE sealing through its C-terminal winged helix (WH) domain, which directly binds and activates the conserved endosomal sorting complex required for transport (ESCRT)-II/ESCRT-III hybrid protein CHMP7
GO:0005637 nuclear inner membrane	IBA GO_REF:0000033	ACCEPT	Summary: Nuclear inner membrane - specific INM protein. Reason: Core localization.
GO:0034399 nuclear periphery	IBA GO_REF:0000033	ACCEPT	Summary: Nuclear periphery - INM localization. Reason: Core localization.
GO:0005635 nuclear envelope	IEA GO_REF:0000044	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005637 nuclear inner membrane	IEA GO_REF:0000044	ACCEPT	Summary: Nuclear inner membrane - specific INM protein. Reason: Core localization.
GO:0005819 spindle	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: Spindle - NE reformation during mitosis. Reason: Cell division context.
GO:0005515 protein binding	IPI PMID:28514442 Architecture of the human interactome defines protein commun...	MARK AS OVER ANNOTATED	Summary: Protein binding from HTP interactome study - generic term per CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule adaptor activity in core_functions) capture the actual scaffold/adapter role. Reason: Per CLAUDE.md, avoid the generic protein-binding term when more specific MFs are available; PR Supporting Evidence: PMID:28514442 Architecture of the human interactome defines protein communities and disease networks.
GO:0005515 protein binding	IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling...	MARK AS OVER ANNOTATED	Summary: Protein binding from HTP interactome study - generic term per CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule adaptor activity in core_functions) capture the actual scaffold/adapter role. Reason: Per CLAUDE.md, avoid the generic protein-binding term when more specific MFs are available; PR Supporting Evidence: PMID:33961781 2021 May 6. Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
GO:0022008 neurogenesis	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: Neurogenesis - developmental role. Reason: Broad developmental process.
GO:0031965 nuclear membrane	IEA GO_REF:0000120	ACCEPT	Summary: Nuclear membrane - general NE localization. Reason: Core localization.
GO:0035914 skeletal muscle cell differentiation	IEA GO_REF:0000120	ACCEPT	Summary: Skeletal muscle cell differentiation - myoblast differentiation. Reason: Differentiation role.
GO:0043409 negative regulation of MAPK cascade	IEA GO_REF:0000107	ACCEPT	Summary: Negative regulation of MAPK cascade - regulates ERK pathway. Reason: Signaling regulation.
GO:0051898 negative regulation of phosphatidylinositol 3-kinase/protein kinase B signal transduction	IEA GO_REF:0000107	ACCEPT	Summary: Negative regulation of PI3K/AKT signaling. Reason: Signaling regulation.
GO:0060914 heart formation	IEA GO_REF:0000107	ACCEPT	Summary: Heart formation - essential for cardiac development. Knockin mice with the human p.L13R LEM-domain mutation develop dilated cardiomyopathy and cardiac fibrosis; cardiomyocyte-specific Lemd2 KO mice die in the neonatal period from cardiac abnormalities. Reason: Core cardiac role supported by KI and conditional KO mouse models. Supporting Evidence: PMID:36377660 We generated knockin (KI) mice carrying the human c.T38>G Lemd2 mutation, which causes a missense amino acid exchange (p.L13>R) in the LEM domain of the protein. These mice represent a preclinical model that phenocopies the human disease, as they developed severe dilated cardiomyopathy and cardiac fibrosis leading to premature death. file:human/LEMD2/LEMD2-deep-research-falcon.md A 2022 Journal of Clinical Investigation study created a knock-in mouse carrying the human disease allele c.T38>G (p.L13R) and showed severe dilated cardiomyopathy and fibrosis. Importantly, cardiomyocyte-specific AAV-mediated Lemd2 gene therapy rescued cardiac function in KI/KI mice.
GO:0031965 nuclear membrane	IDA GO_REF:0000052	ACCEPT	Summary: Nuclear membrane - general NE localization. Reason: Core localization.
GO:0000785 chromatin	IDA PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	ACCEPT	Summary: Chromatin - organizes heterochromatin at NE. Cardiomyocyte-specific loss of LEMD2 disorganizes the transcriptionally silent heterochromatin associated with the nuclear envelope. Reason: Core function supported by mouse models. Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells. PMID:36377660 At the cellular level, KI/KI cardiomyocytes exhibited disorganization of the transcriptionally silent heterochromatin associated with the nuclear envelope.
GO:0005635 nuclear envelope	IDA PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization. Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.
GO:0005783 endoplasmic reticulum	IDA PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	KEEP AS NON CORE	Summary: ER - INM is continuous with ER but distinct. Reason: Related but distinct compartment. Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.
GO:0016020 membrane	TAS PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	ACCEPT	Summary: Membrane - transmembrane protein. Reason: General membrane. Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.
GO:0071168 protein localization to chromatin	IMP PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	KEEP AS NON CORE	Summary: Protein localization to chromatin annotation — the original PMID:28242692 reference is about ESCRT-mediated NE closure, NOT chromatin tethering (PR #758 review feedback). The biologically valid support for chromatin- tethering comes from LEMD2's LEM-domain interactions with BAF and lamins (the chromatin–NE tethering axis), captured separately by GO:0000785 chromatin and supported by PMID:36377660 below. Annotation kept as KEEP_AS_NON_CORE pending re-citation; the original PMID:28242692 supporting_text does not address chromatin-localization mechanism. Reason: The annotation is biologically plausible (via LEM-domain-BAF tethering), but the original PMID:28242692 reference does not directly establish chromatin localization; downgraded from ACCEPT pending a primary reference that directly demonstrates LEMD2-mediated chromatin protein localization.
GO:0005515 protein binding	IPI PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	MARK AS OVER ANNOTATED	Summary: Protein binding from HTP interactome study - generic term per CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule adaptor activity in core_functions) capture the actual scaffold/adapter role. Reason: Per CLAUDE.md, avoid the generic protein-binding term when more specific MFs are available; PR Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.
GO:0005637 nuclear inner membrane	TAS PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope clos...	ACCEPT	Summary: Nuclear inner membrane - specific INM protein. Reason: Core localization. Supporting Evidence: PMID:28242692 LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.
GO:0006998 nuclear envelope organization	IMP PMID:17097643 The inner nuclear membrane protein Lem2 is critical for norm...	ACCEPT	Summary: Nuclear envelope organization - primary function. LEMD2/LEM2 together with CHMP7 seals NE holes around spindle microtubules during mitotic exit; redundant with BAF-LEM-mediated hole closure. Reason: Core process supported by mechanistic studies in human cells and C. elegans. Supporting Evidence: PMID:17097643 Epub 2006 Nov 3. The inner nuclear membrane protein Lem2 is critical for normal nuclear envelope morphology. PMID:37795681 The LAP2-emerin-MAN1 (LEM)-domain protein LEMD2 and ESCRT-II/III hybrid protein CHMP7 close NE holes surrounding spindle microtubules (MTs). file:human/LEMD2/LEMD2-deep-research-falcon.md In nuclear-envelope maintenance, CHMP7 together with INM LEMD2 is implicated in sealing small nuclear-envelope holes, whereas repair of larger ruptures can depend more strongly on BAF-mediated mechanisms.
GO:0016020 membrane	HDA PMID:19946888 Defining the membrane proteome of NK cells.	ACCEPT	Summary: Membrane - transmembrane protein. Reason: General membrane. Supporting Evidence: PMID:19946888 Defining the membrane proteome of NK cells.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668335	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668389	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668395	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668398	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668405	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668415	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005635 nuclear envelope	TAS Reactome:R-HSA-9668419	ACCEPT	Summary: Nuclear envelope - core localization. Reason: Primary localization.
GO:0005637 nuclear inner membrane	IDA PMID:16339967 LEM2 is a novel MAN1-related inner nuclear membrane protein ...	ACCEPT	Summary: Nuclear inner membrane - specific INM protein. Reason: Core localization. Supporting Evidence: PMID:16339967 LEM2 is a novel MAN1-related inner nuclear membrane protein associated with A-type lamins.
GO:0035914 skeletal muscle cell differentiation	IGI PMID:19720741 Overlapping functions of nuclear envelope proteins NET25 (Le...	ACCEPT	Summary: Skeletal muscle cell differentiation - myoblast differentiation. Reason: Differentiation role. Supporting Evidence: PMID:19720741 Aug 31. Overlapping functions of nuclear envelope proteins NET25 (Lem2) and emerin in regulation of extracellular signal-regulated kinase signaling in myoblast differentiation.
GO:0006325 chromatin organization	NAS	NEW	Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations. Supporting Evidence: file:human/LEMD2/LEMD2-uniprot.txt LEMD2 is INM protein with LEM domain. Essential for NE integrity and repair via ESCRT. Mutations cause arrhythmic cardiomyopathy.

Core Functions

ESCRT adapter at inner nuclear membrane that binds lamins, BAF, and CHMP7/IST1/CHMP2A. Mediates chromatin-nuclear envelope connection and recruits ESCRT-III machinery for nuclear envelope repair and closure during cell division. The molecular_function GO:0030674 (protein- macromolecule adaptor activity) replaces the previously-listed generic GO:0005515 (protein binding) per PR #758 review feedback and CLAUDE.md guidance against the generic protein-binding term.

Molecular Function:

protein-macromolecule adaptor activity

Directly Involved In:

nuclear envelope organization chromatin organization

Cellular Locations:

nuclear inner membrane

Supporting Evidence:

file:human/LEMD2/LEMD2-uniprot.txt
LEMD2 is INM protein with LEM domain. Essential for NE integrity and repair via ESCRT. Mutations cause arrhythmic cardiomyopathy.

References

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt.

GO_REF:0000052

Gene Ontology annotation based on curation of immunofluorescence data

GO_REF:0000107

Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara.

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods.

PMID:16339967

LEM2 is a novel MAN1-related inner nuclear membrane protein associated with A-type lamins.

PMID:17097643

The inner nuclear membrane protein Lem2 is critical for normal nuclear envelope morphology.

LEM2 is required for normal nuclear envelope morphology.

"The inner nuclear membrane protein Lem2 is critical for normal nuclear envelope morphology."

PMID:36377660

Loss of function of the nuclear envelope protein LEMD2 causes DNA damage-dependent cardiomyopathy.

Knockin mice carrying the human LEMD2 c.T38>G (p.L13R) LEM-domain mutation phenocopy human disease, developing severe dilated cardiomyopathy and cardiac fibrosis; cardiomyocyte-specific Lemd2 KO mice die shortly after birth from cardiac abnormalities with extensive DNA damage and p53 activation, and AAV-mediated cardiomyocyte-specific Lemd2 delivery rescues cardiac function.

"We generated knockin (KI) mice carrying the human c.T38>G Lemd2 mutation, which causes a missense amino acid exchange (p.L13>R) in the LEM domain of the protein. These mice represent a preclinical model that phenocopies the human disease, as they developed severe dilated cardiomyopathy and cardiac fibrosis leading to premature death. At the cellular level, KI/KI cardiomyocytes exhibited disorganization of the transcriptionally silent heterochromatin associated with the nuclear envelope. Moreover, mice with cardiac-specific deletion of Lemd2 also died shortly after birth due to heart abnormalities. Cardiomyocytes lacking Lemd2 displayed nuclear envelope deformations and extensive DNA damage and apoptosis linked to p53 activation. Importantly, cardiomyocyte-specific Lemd2 gene therapy via adeno-associated virus rescued cardiac function in KI/KI mice."
LEMD2 is an INM protein with a LEM domain and two transmembrane domains that mediates interaction between chromatin and the NE via association with lamins and BAF.

"LEM domain–containing protein 2 (LEMD2), which is expressed ubiquitously, is characterized by the presence of the LEM domain and 2 transmembrane domains. A series of in vitro studies revealed its ability to associate with DNA-binding proteins such as lamins and barrier-to-autointegration factor (BAF), which implicates LEMD2 as a mediator of the interaction between chromatin and the NE"

PMID:37795681

Nuclear envelope assembly relies on CHMP-7 in the absence of BAF-LEM-mediated hole closure.

LEMD2 contributes to NE sealing through its C-terminal winged helix (WH) domain, which directly binds and activates CHMP7; the WH of LEMD2 copolymerizes with CHMP7 to form 50-100 nm rings on the cytosolic surface of NE holes to restrict diffusion. The WH domain of LEM-2 (C. elegans LEMD2 homolog) recruits CHMP-7 to the NE; LEM-2-CHMP-7 function is essential for NE assembly when BAF-LEM binding is compromised.

"The LEM-domain protein LEMD2 contributes to NE sealing through its C-terminal winged helix (WH) domain, which directly binds and activates the conserved endosomal sorting complex required for transport (ESCRT)-II/ESCRT-III hybrid protein CHMP7 (Gatta et al., 2021; Gu et al., 2017; von Appen et al., 2020). The WH of LEMD2 copolymerizes with CHMP7 to form 50–100 nm rings in vitro and it is thought that the assembly of these rings on the cytosolic surface of NE holes restricts the diffusion of macromolecules"

PMID:39208110

Micronuclear collapse from oxidative damage.

Mitochondria-derived ROS disrupt micronuclear integrity through a pathological axis in which ROS-induced cysteine oxidation stimulates CHMP7 oligomerization and aberrant binding to LEMD2, disrupting micronuclear envelopes and engendering chromosome shattering. This axis mediates micronuclear disintegrity under hypoxic conditions, linking tumor microenvironment stress to aberrant engagement of the LEMD2-CHMP7 module.

"ROS-induced cysteine oxidation stimulated CHMP7 oligomerization and binding to the nuclear membrane protein LEMD2, disrupting micronuclear envelopes. Furthermore, this ROS-CHMP7 pathological axis engendered chromosome shattering known to result from micronuclear rupture. It also mediated micronuclear disintegrity under hypoxic conditions, linking tumor microenvironment"
The ESCRT-III complex mediates nuclear envelope repair by assembling through binding to LEMD2 and CHMP7 scaffolds at nuclear membrane rupture sites.

"The endosomal sorting complex required for transport III (ESCRT-III) complex is a key player in mediating nuclear envelope repair, and it assembles through binding to LEM domain nuclear envelope protein 2 (LEMD2) and charged multivesicular body protein 7 (CHMP7) scaffolds at the nuclear membrane rupture sites"

file:human/LEMD2/LEMD2-deep-research-falcon.md

Deep research on LEMD2 function (falcon)

LEMD2/LEM2 acts as a chromatin-lamina-ESCRT integrator at the inner nuclear membrane; its N-terminal LEM domain binds BAF and lamins, a low-complexity region undergoes liquid-liquid phase separation at spindle-associated membrane gaps, and the C-terminal winged-helix/MSC domain binds and activates CHMP7 to nucleate ESCRT-III-mediated NE sealing. The CHMP7/LEMD2 module preferentially seals small NE holes (<100 nm), while BAF-driven mechanisms dominate at larger ruptures.

"Mechanistically, LEM2/LEMD2 can recruit/activate CHMP7 via a C-terminal WH/MSC domain; CHMP7 then nucleates downstream ESCRT-III assembly for membrane sealing."

PMID:19720741

Overlapping functions of nuclear envelope proteins NET25 (Lem2) and emerin in regulation of extracellular signal-regulated kinase signaling in myoblast differentiation.

PMID:19946888

Defining the membrane proteome of NK cells.

PMID:28242692

LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in fission yeast and human cells.

PMID:28514442

Architecture of the human interactome defines protein communities and disease networks.

PMID:33961781

Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.

Reactome:R-HSA-9668335

CHMP7 binds LEMD2

Reactome:R-HSA-9668389

VPS4 binds ESCRT-III assemblies at nuclear envelope (NE) fenestrations

Reactome:R-HSA-9668395

CHMP7 binds CC2D1B

Reactome:R-HSA-9668398

CHMP7 binds CHMP4B, which recruits other subunits of the ESCRT-III complex

Reactome:R-HSA-9668405

SPAST (spastin) binds the IST1 subunit of ESCRT-III at the sites of microtubule attachment to chromatin

Reactome:R-HSA-9668415

VPS4 mediates disassembly of ESCRTIII subunits to promote sealing of holes in the nuclear envelope

Reactome:R-HSA-9668419

SPAST (spastin) mediates the severing of microtubules at chromosome attachment sites

file:human/LEMD2/LEMD2-deep-research-perplexity-lite.md

Deep research on LEMD2 function

Deep Research

Falcon

(LEMD2-deep-research-falcon.md)

Research Report: Human **LEMD2** (UniProt Q8NC56) — functional annotation, pathways, and disease relevance Falcon Edison Scientific Literature 40 citations 2 artifacts 2026-05-29T19:29:16.171370

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000043 The schematic figure illustrating the ROS–CHMP7–LEMD2 mechanism of micronuclear collapse is found on page 3 of the document. It det (image/png)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
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We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

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Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Human LEMD2 (UniProt Q8NC56) — functional annotation, pathways, and disease relevance

0) Identity verification (critical)

The target is human LEMD2 (UniProt Q8NC56), also referred to in the literature as LEM2 / LEM domain-containing protein 2, an integral inner nuclear membrane (INM) protein with a LEM domain and a C-terminal winged-helix (WH)/MAN1-like (MSC) domain. Multiple retrieved sources explicitly describe LEMD2 as an INM protein and describe the LEM-domain → BAF binding and the WH/MSC → CHMP7/ESCRT-III interaction axis that matches the UniProt domain expectations. (caravia2022lossoffunction pages 1-2, johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 22-27)

1) Key concepts and definitions (current understanding)

1.1 LEM-domain proteins

LEM-domain proteins (LAP2–emerin–MAN1 family) are nuclear envelope-associated factors, typically INM localized, that connect chromatin and the nuclear lamina to nuclear-envelope structure and signaling. A defining feature is the LEM domain, described as a ~40 amino-acid bi-helical motif that binds Barrier-to-Autointegration Factor (BAF), a chromatin-associated protein. (nair2025nuclearenvelopeand pages 8-10)

1.2 LEMD2 (LEM2) core cell-biological role

LEMD2 is described as a ubiquitously expressed INM protein with a conserved N-terminal LEM domain and two transmembrane segments, localizing at the nuclear periphery. Its LEM domain enables association with DNA-associated proteins including lamins and BAF, supporting a chromatin–nuclear envelope tethering function. (caravia2022lossoffunction pages 1-2)

1.3 ESCRT-III and the LEMD2–CHMP7 “compartmentalization sensor” module

The ESCRT-III machinery is a membrane-remodeling system whose controlled polymerization can seal small membrane discontinuities. In nuclear-envelope maintenance, CHMP7 together with INM LEMD2 is implicated in sealing small nuclear-envelope holes, whereas repair of larger ruptures can depend more strongly on BAF-mediated mechanisms. (keeley2024nuclearanddegradative pages 3-4)

Mechanistically, LEM2/LEMD2 can recruit/activate CHMP7 via a C-terminal WH/MSC domain; CHMP7 then nucleates downstream ESCRT-III assembly for membrane sealing. (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 22-27)

2) Molecular functions, domains, and localization (functional annotation)

2.1 Subcellular localization

LEMD2 is an integral inner nuclear membrane protein at the nuclear periphery. (caravia2022lossoffunction pages 1-2)

2.2 Domain-to-function mapping

A structured domain/function mapping is provided below.

Domain/region (approx. position)	Key binding partners	Cellular process/function	Key evidence (paper, year, DOI/URL)	Notes
N-terminal LEM domain (~40 aa motif; pathogenic p.L13R falls within this region)	BAF; lamins/chromatin-associated proteins	Tethers chromatin/heterochromatin to the inner nuclear membrane (INM); contributes to nuclear envelope (NE) integrity, chromatin stabilization, and post-mitotic NE reformation	Caravia et al., 2022, J Clin Invest, https://doi.org/10.1172/jci158897; Nair et al., 2025, Nucleus, https://doi.org/10.1080/19491034.2024.2449520 (caravia2022lossoffunction pages 1-2, nair2025nuclearenvelopeand pages 8-10)	LEM domain is described as a ~40 aa bihelical BAF-binding motif in LEM-family proteins; p.L13R reduces function and is associated with cardiomyopathy phenotypes (caravia2022lossoffunction pages 1-2, nair2025nuclearenvelopeand pages 8-10, lipov2023exploringthecomplex pages 3-4).
N-terminal region / LEM-domain-containing chromatin-targeting module (NTD; includes LEM domain)	BAF-coated chromatin	Targets LEMD2/LEM2 to anaphase chromatin and reforming NE; helps establish early nucleocytoplasmic compartmentalization	Johnson/von Appen, 2020, mechanistic LEM2 study (DOI not available in retrieved text); Keeley & Coyne, 2024, Nucleus, https://doi.org/10.1080/19491034.2024.2349085 (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 22-27, keeley2024nuclearanddegradative pages 3-4)	In mechanistic models, BAF–LEM engagement positions LEM2 at NE holes/fenestrations before ESCRT-III recruitment; 2024 review notes CHMP7/LEMD2 mainly seal small holes, while larger ruptures rely more on BAF-mediated mechanisms (johnson2020discoveringhowinner pages 13-16, keeley2024nuclearanddegradative pages 3-4).
Low-complexity domain (LCD) / phase-separating region (approx. aa 43–202; NTD aa 1–208 in LEM2 study)	Microtubules; chromatin-proximal membrane environment	Promotes local condensation/phase separation at spindle-associated membrane gaps during mitotic NE reformation; helps spatially organize membrane sealing machinery	Johnson/von Appen, 2020, mechanistic LEM2 study (DOI not available in retrieved text); Borah et al., 2022, Front Cell Dev Biol, https://doi.org/10.3389/fcell.2022.989217 (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 35-39, borah2022thelemescrttoolkit pages 1-3)	Undergoes liquid-like phase separation; contains a microtubule-targeting/basic subregion; phosphomimetic changes block condensation, implying cell-cycle regulation (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 35-39).
Proline/arginine-rich microtubule-binding segment near first transmembrane helix (exact aa not fully resolved in retrieved evidence)	Spindle microtubules	Couples NE reformation to spindle disassembly/clearance; concentrates LEM2 at microtubule-occupied fenestrations	Johnson/von Appen, 2020, mechanistic LEM2 study (DOI not available in retrieved text) (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 35-39)	Supports a model in which LEMD2 bridges membranes, chromatin, and spindle microtubules to prevent persistent NE openings and genome damage (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 35-39).
Two transmembrane segments / membrane-embedded core	INM membrane environment; nuclear lamina-associated network	Anchors LEMD2 as an integral INM protein, enabling it to act as a chromatin–lamina tether and compartmentalization sensor at NE ruptures	Caravia et al., 2022, J Clin Invest, https://doi.org/10.1172/jci158897; Nair et al., 2025, Nucleus, https://doi.org/10.1080/19491034.2024.2449520; Borah et al., 2022, Front Cell Dev Biol, https://doi.org/10.3389/fcell.2022.989217 (caravia2022lossoffunction pages 1-2, nair2025nuclearenvelopeand pages 8-10, borah2022thelemescrttoolkit pages 3-4)	Caravia explicitly describes LEMD2 as an INM protein with two transmembrane segments; family reviews place LEMD2 among INM LEM proteins that cooperate with lamins and ESCRT pathways (caravia2022lossoffunction pages 1-2, nair2025nuclearenvelopeand pages 8-10).
C-terminal winged-helix (WH) / MSC / MAN1-like domain (AA ~395–503 in LEM2 study)	CHMP7 directly; downstream ESCRT-III factors indirectly (e.g., IST1)	Recruits and activates CHMP7; nucleates ESCRT-III assembly for NE sealing/reformation and rupture repair	Johnson/von Appen, 2020, mechanistic LEM2 study (DOI not available in retrieved text); Keeley & Coyne, 2024, Nucleus, https://doi.org/10.1080/19491034.2024.2349085 (johnson2020discoveringhowinner pages 22-27, johnson2020discoveringhowinner pages 13-16, keeley2024nuclearanddegradative pages 3-4)	Direct CHMP7-binding interface; relieves CHMP7 autoinhibition and induces polymerization; central to sealing small NE holes (<100 nm) per 2024 review (johnson2020discoveringhowinner pages 22-27, keeley2024nuclearanddegradative pages 3-4).
LEMD2–CHMP7 functional module at NE ruptures/interphase repair sites (multi-domain emergent activity rather than single motif)	CHMP7, ESCRT-III machinery, BAF-assisted rupture context	Acts as a compartmentalization sensor that initiates ESCRT-III-dependent membrane repair at exposed chromatin/ruptures	Borah et al., 2022, Front Cell Dev Biol, https://doi.org/10.3389/fcell.2022.989217; Keeley & Coyne, 2024, Nucleus, https://doi.org/10.1080/19491034.2024.2349085 (borah2022thelemescrttoolkit pages 3-4, keeley2024nuclearanddegradative pages 3-4)	Reviews synthesize LEMD2 as part of the conserved “LEM-ESCRT toolkit”; exposure of LEM proteins to cytosol after rupture activates/recruits CHMP7 and downstream ESCRT-III (borah2022thelemescrttoolkit pages 3-4, keeley2024nuclearanddegradative pages 3-4).
Full-length LEMD2/LEM2 as chromatin–lamina–ESCRT integrator	BAF, lamins, CHMP7, microtubules	Maintains genome stability by integrating chromatin tethering, lamina association, membrane remodeling, and NE repair/reformation	Caravia et al., 2022, J Clin Invest, https://doi.org/10.1172/jci158897; Johnson/von Appen, 2020; Nair et al., 2025, Nucleus, https://doi.org/10.1080/19491034.2024.2449520; Borah et al., 2022, Front Cell Dev Biol, https://doi.org/10.3389/fcell.2022.989217; Keeley & Coyne, 2024, Nucleus, https://doi.org/10.1080/19491034.2024.2349085 (caravia2022lossoffunction pages 1-2, johnson2020discoveringhowinner pages 13-16, nair2025nuclearenvelopeand pages 8-10, borah2022thelemescrttoolkit pages 3-4, keeley2024nuclearanddegradative pages 3-4)	Loss of function causes NE deformation, DNA damage, p53 activation, apoptosis, and cardiomyopathy in vivo; this broader phenotype is consistent with failure of both structural tethering and ESCRT-coupled repair functions (caravia2022lossoffunction pages 1-2, keeley2024nuclearanddegradative pages 3-4).

Table: This table maps the major structural regions of human LEMD2/LEM2 to their known binding partners and molecular functions at the inner nuclear membrane. It is useful for functional annotation because it links UniProt-style domain architecture to experimentally supported roles in chromatin tethering, microtubule-associated nuclear envelope reformation, and CHMP7/ESCRT-III-mediated repair.

2.3 Mechanistic model (mitosis and interphase)

Mitotic nuclear envelope reformation (open mitosis): Mechanistic work on LEM2 (ortholog of human LEMD2) describes it as a two-pass INM protein that coordinates ESCRT-mediated sealing during mitotic exit. The LEM domain binds BAF to target chromatin; a low-complexity region can phase-separate, and a microtubule-binding region focuses LEM2 at spindle-associated fenestrations. The C-terminal WH/MSC domain binds and activates CHMP7, promoting CHMP7 polymerization and recruitment of downstream ESCRT-III factors for NE sealing and early compartmentalization. (johnson2020discoveringhowinner pages 13-16, johnson2020discoveringhowinner pages 22-27)

Interphase rupture repair: Reviews synthesize a conserved “LEM–ESCRT toolkit” where exposure of LEM proteins at ruptures recruits CHMP7 and downstream ESCRT-III machinery, contributing to NE repair and maintenance. (borah2022thelemescrttoolkit pages 3-4, keeley2024nuclearanddegradative pages 3-4)

3) Recent developments and latest research (prioritizing 2023–2024)

3.1 2023: Redundancy between BAF–LEM and LEM2–CHMP7 pathways in NE sealing

A 2023 study in Journal of Cell Science (C. elegans) provides primary evidence that LEM-2’s WH domain activates CHMP-7 to support ESCRT-III polymerization and NE closure, and that CHMP-7 becomes critical when BAF–LEM-mediated closure is compromised—supporting a redundancy/fallback model. While not human, it is explicitly framed in terms of homology (LEM-2 ↔ human LEMD2; CHMP-7 ↔ human CHMP7) and supports conserved mechanistic logic used in human models. (barger2023nuclearenvelopeassembly pages 12-14)

Publication date/URL: Nov 2023; https://doi.org/10.1242/jcs.261385 (barger2023nuclearenvelopeassembly pages 12-14)

3.2 2024: Direct connection of LEMD2–CHMP7 to micronuclear collapse under oxidative stress (Science)

A 2024 Science paper reports a pathological axis in which mitochondrial reactive oxygen species (ROS) promote CHMP7 cysteine oxidation, CHMP7 oligomerization, and enhanced binding to LEMD2, while disrupting CHMP7 interactions with canonical ESCRT-III partners. This shift is associated with micronuclear envelope collapse, chromosome shattering, and inflammation, and occurs under hypoxic conditions—connecting tumor microenvironment stress to aberrant engagement of the LEMD2–CHMP7 module. (bona2024micronuclearcollapsefrom pages 1-3)

Publication date/URL: Aug 2024; https://doi.org/10.1126/science.adj8691 (bona2024micronuclearcollapsefrom pages 1-3)

3.3 2024: Experimental/technical real-time interrogation of LEMD2–CHMP7 recruitment at ruptures

A 2024 Frontiers in Cell and Developmental Biology methods paper introduces a deterministic rupture/live-imaging pipeline and states that CHMP7–LEMD2 binding is the fundamental step enabling ESCRT-III recruitment to rupture sites, illustrating direct real-world experimental implementation for measuring recruitment dynamics at primary nuclei and micronuclei. (bona2024anewmicroscopy pages 1-2)

Publication date/URL: Sep 2024; https://doi.org/10.3389/fcell.2024.1475095 (bona2024anewmicroscopy pages 1-2)

3.4 2024: Review synthesis (neurodegeneration angle)

A 2024 review (Nucleus) synthesizes that CHMP7/LEMD2 are involved in sealing small (<100 nm) nuclear-envelope holes, whereas BAF is emphasized for larger ruptures; it also emphasizes that nuclear ESCRT requirements may differ across cell types (e.g., neurons vs immortalized lines), highlighting an open problem in translating cell biology to disease contexts. (keeley2024nuclearanddegradative pages 3-4)

Publication date/URL: May 2024; https://doi.org/10.1080/19491034.2024.2349085 (keeley2024nuclearanddegradative pages 3-4)

4) Current applications and real-world implementations

4.1 Preclinical gene therapy for LEMD2-associated cardiomyopathy (proof of concept)

A 2022 Journal of Clinical Investigation study created a knock-in mouse carrying the human disease allele c.T38>G (p.L13R) and showed severe dilated cardiomyopathy and fibrosis. Importantly, cardiomyocyte-specific AAV-mediated Lemd2 gene therapy rescued cardiac function in KI/KI mice, supporting a direct therapeutic concept for LEMD2-related cardiomyopathy (preclinical). (caravia2022lossoffunction pages 1-2, caravia2022lossoffunction pages 9-11)

Publication date/URL: Nov 2022; https://doi.org/10.1172/jci158897 (caravia2022lossoffunction pages 1-2)

4.2 Oncology: LEMD2 as a candidate cancer vulnerability/biomarker target class (preclinical)

A 2024 study in triple-negative breast cancer (TNBC) contexts reported that siRNA depletion of Lem-D family proteins (including LEMD2) in TNBC cell lines induced aberrant nuclear morphology, reduced proliferation, and cell death, with minimal effects in non-cancerous breast cells—supporting a hypothesis that INM LEM proteins may represent context-dependent vulnerabilities. (rose2024theexpressionand pages 1-2)

Publication date/URL: Apr 2024; https://doi.org/10.3389/fonc.2024.1222698 (rose2024theexpressionand pages 1-2)

4.3 Micronuclei rupture assays and repair-pathway profiling

The 2024 microscopy pipeline provides a standardized assay framework to study recruitment of LEMD2 and CHMP7 at ruptures (primary nuclei and micronuclei), enabling broader adoption of mechanistic nuclear-envelope repair measurements. (bona2024anewmicroscopy pages 1-2)

5) Expert opinions and analysis (authoritative synthesis)

5.1 Functional partitioning: small-hole sealing vs large-rupture plugging

An emerging consensus is that LEMD2–CHMP7–ESCRT-III is well suited to seal small nuclear-envelope holes, while BAF-driven responses can dominate in large ruptures—implying parallel and partly redundant repair routes. This helps interpret why perturbing one component yields context-specific phenotypes across cell types and model systems. (keeley2024nuclearanddegradative pages 3-4, barger2023nuclearenvelopeassembly pages 12-14)

5.2 Disease mechanism framing

Mechanistic cardiomyopathy models support a view that LEMD2 protects mechanically stressed post-mitotic cells (cardiomyocytes) by maintaining nuclear-envelope integrity and genome stability; failure leads to DNA damage, p53 activation, apoptosis, fibrosis, and arrhythmia susceptibility. (caravia2022lossoffunction pages 1-2, caravia2022lossoffunction pages 9-11, ravera2025cardiovascularinvolvementin pages 8-9)

5.3 Cancer relevance: “too much” versus “too little” repair

The 2024 Science study suggests that the LEMD2–CHMP7 module can become pathological under oxidative stress/hypoxia by driving micronuclear collapse; thus, therapeutic manipulation of this axis would need to consider the trade-off between facilitating repair and avoiding deleterious hyperactivation/mislocalization. (bona2024micronuclearcollapsefrom pages 1-3)

6) Key statistics and quantitative data (recent and foundational)

6.1 Human genetics (from 2023 synthesis)

A 2023 cardiomyopathy genetics synthesis reports for LEMD2: 2 families and 11 biallelic cases, with exome evidence from two large pedigrees and an estimated Max LOD = 7.3. (lipov2023exploringthecomplex pages 3-4)

Publication date/URL: Oct 2023; https://doi.org/10.1038/s44161-023-00346-3 (lipov2023exploringthecomplex pages 3-4)

6.2 Preclinical therapy parameters (JCI 2022)

In the KI/KI cardiomyopathy model, AAV9-Lemd2 was delivered at 5 × 10^13 vg/kg (P4), with echocardiography at 2 months. Sample sizes included WT n=7, KI/KI n=10, and KI/KI + AAV9-Lemd2 n=4. Lemd2 mRNA was increased >10-fold after AAV, with protein restoration near WT. (caravia2022lossoffunction pages 9-11)

6.3 Survival/lethality in mouse models (JCI 2022)

Cardiomyocyte-specific knockout had median survival of 2 days (caravia2022lossoffunction pages 9-11). An additional excerpt reports 50% mortality by postnatal day 2 and a survival analysis comparing controls (n=19) and cKO (n=23) with ****P<0.0001. (caravia2022lossoffunction pages 7-9, caravia2022lossoffunction pages 6-7)

6.4 Variant impact on expression and conduction phenotypes

A narrative review cites a homozygous Lemd2 p.L13R knock-in model with Lemd2 mRNA reduced to 65%, reduced protein levels, and conduction abnormalities (PR/QRS prolongation) at 6 months, preceding pronounced LV dilation at 9 months. (ravera2025cardiovascularinvolvementin pages 8-9)

6.5 Mechanistic size/geometry constraints

A 2024 review states CHMP7/LEMD2 seal small NE holes such as <100 nm. (keeley2024nuclearanddegradative pages 3-4)

Foundational mechanistic measurements in LEM2/CHMP7 polymerization report WH-induced CHMP7 polymers with variable inner diameters ~50–100 nm. (johnson2020discoveringhowinner pages 22-27)

7) Visual evidence: ROS–CHMP7–LEMD2 model

A schematic from the 2024 Science study illustrates the ROS-driven CHMP7 oligomerization and aberrant binding to LEMD2 leading to micronuclear collapse. (bona2024micronuclearcollapsefrom media c1457801, bona2024micronuclearcollapsefrom pages 1-3)

8) Limitations and evidence gaps (within retrieved corpus)

Progeroid-syndrome specifics for LEMD2 (e.g., Marbach–Rustad progeroid syndrome clinical series) were referenced in retrieved documents but the core case-report/phenotype-expansion papers were not obtainable in this run, so detailed phenotype frequencies/statistics for those syndromes are not included here. (caravia2022lossoffunction pages 7-9)
Several mechanistic claims about lipid composition and “regulated lipid synthesis with LEM2/CHMP7” were cited indirectly in the 2023 JCS paper’s discussion, but the primary lipid-focused papers themselves were not retrieved in full text here. (barger2023nuclearenvelopeassembly pages 25-27)

References (URLs, dates)

Caravia XM et al. Loss of function of the nuclear envelope protein LEMD2 causes DNA damage–dependent cardiomyopathy. J Clin Invest. Nov 2022. https://doi.org/10.1172/jci158897 (caravia2022lossoffunction pages 1-2)
Lipov A et al. Exploring the complex spectrum of dominance and recessiveness in genetic cardiomyopathies. Nat Cardiovasc Res. Oct 2023. https://doi.org/10.1038/s44161-023-00346-3 (lipov2023exploringthecomplex pages 3-4)
Barger SR et al. Nuclear envelope assembly relies on CHMP-7 in the absence of BAF–LEM-mediated hole closure. J Cell Sci. Nov 2023. https://doi.org/10.1242/jcs.261385 (barger2023nuclearenvelopeassembly pages 12-14)
Keeley O, Coyne AN. Nuclear and degradative functions of the ESCRT-III pathway: implications for neurodegenerative disease. Nucleus. May 2024. https://doi.org/10.1080/19491034.2024.2349085 (keeley2024nuclearanddegradative pages 3-4)
Di Bona M, Bakhoum SF. A new microscopy pipeline for studying the initial stages of nuclear and micronuclear rupture and repair. Front Cell Dev Biol. Sep 2024. https://doi.org/10.3389/fcell.2024.1475095 (bona2024anewmicroscopy pages 1-2)
Di Bona M et al. Micronuclear collapse from oxidative damage. Science. Aug 2024. https://doi.org/10.1126/science.adj8691 (bona2024micronuclearcollapsefrom pages 1-3)
Rose M et al. The expression and role of the Lem-D proteins Ankle2, Emerin, Lemd2, and TMPO in triple-negative breast cancer cell growth. Front Oncol. Apr 2024. https://doi.org/10.3389/fonc.2024.1222698 (rose2024theexpressionand pages 1-2)
Nair A et al. Nuclear envelope and chromatin choreography direct cellular differentiation. Nucleus. Feb 2025. https://doi.org/10.1080/19491034.2024.2449520 (nair2025nuclearenvelopeand pages 8-10)
Borah S et al. The LEM-ESCRT toolkit: Repair and maintenance of the nucleus. Front Cell Dev Biol. Sep 2022. https://doi.org/10.3389/fcell.2022.989217 (borah2022thelemescrttoolkit pages 3-4)

References

(caravia2022lossoffunction pages 1-2): Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, and Eric N. Olson. Loss of function of the nuclear envelope protein lemd2 causes dna damage–dependent cardiomyopathy. The Journal of Clinical Investigation, Nov 2022. URL: https://doi.org/10.1172/jci158897, doi:10.1172/jci158897. This article has 23 citations.
(johnson2020discoveringhowinner pages 13-16): IE Johnson. Discovering how inner nuclear membrane protein, lem2, orchestrates timely nuclear envelope reformation during open mitosis. Unknown journal, 2020.
(johnson2020discoveringhowinner pages 22-27): IE Johnson. Discovering how inner nuclear membrane protein, lem2, orchestrates timely nuclear envelope reformation during open mitosis. Unknown journal, 2020.
(nair2025nuclearenvelopeand pages 8-10): Anjitha Nair, Jayati Khanna, Jashan Kler, Rohith Ragesh, and Kundan Sengupta. Nuclear envelope and chromatin choreography direct cellular differentiation. Nucleus, Feb 2025. URL: https://doi.org/10.1080/19491034.2024.2449520, doi:10.1080/19491034.2024.2449520. This article has 4 citations and is from a peer-reviewed journal.
(keeley2024nuclearanddegradative pages 3-4): Olivia Keeley and Alyssa N. Coyne. Nuclear and degradative functions of the escrt-iii pathway: implications for neurodegenerative disease. Nucleus, May 2024. URL: https://doi.org/10.1080/19491034.2024.2349085, doi:10.1080/19491034.2024.2349085. This article has 16 citations and is from a peer-reviewed journal.
(lipov2023exploringthecomplex pages 3-4): Alex Lipov, Sean J. Jurgens, Francesco Mazzarotto, Mona Allouba, James P. Pirruccello, Yasmine Aguib, Massimo Gennarelli, Magdi H. Yacoub, Patrick T. Ellinor, Connie R. Bezzina, and Roddy Walsh. Exploring the complex spectrum of dominance and recessiveness in genetic cardiomyopathies. Nature Cardiovascular Research, 2:1078-1094, Oct 2023. URL: https://doi.org/10.1038/s44161-023-00346-3, doi:10.1038/s44161-023-00346-3. This article has 39 citations and is from a peer-reviewed journal.
(johnson2020discoveringhowinner pages 35-39): IE Johnson. Discovering how inner nuclear membrane protein, lem2, orchestrates timely nuclear envelope reformation during open mitosis. Unknown journal, 2020.
(borah2022thelemescrttoolkit pages 1-3): Sapan Borah, Karthigeyan Dhanasekaran, and Santosh Kumar. The lem-escrt toolkit: repair and maintenance of the nucleus. Frontiers in Cell and Developmental Biology, Sep 2022. URL: https://doi.org/10.3389/fcell.2022.989217, doi:10.3389/fcell.2022.989217. This article has 13 citations.
(borah2022thelemescrttoolkit pages 3-4): Sapan Borah, Karthigeyan Dhanasekaran, and Santosh Kumar. The lem-escrt toolkit: repair and maintenance of the nucleus. Frontiers in Cell and Developmental Biology, Sep 2022. URL: https://doi.org/10.3389/fcell.2022.989217, doi:10.3389/fcell.2022.989217. This article has 13 citations.
(barger2023nuclearenvelopeassembly pages 12-14): Sarah R. Barger, Lauren Penfield, and Shirin Bahmanyar. Nuclear envelope assembly relies on chmp-7 in the absence of baf–lem-mediated hole closure. Journal of Cell Science, Nov 2023. URL: https://doi.org/10.1242/jcs.261385, doi:10.1242/jcs.261385. This article has 10 citations and is from a domain leading peer-reviewed journal.
(bona2024micronuclearcollapsefrom pages 1-3): Melody Di Bona, Yanyang Chen, Albert S. Agustinus, Alice Mazzagatti, Mercedes A. Duran, Matthew Deyell, Daniel Bronder, James Hickling, Christy Hong, Lorenzo Scipioni, Giulia Tedeschi, Sara Martin, Jun Li, Aušrinė Ruzgaitė, Nadeem Riaz, Parin Shah, Edridge K. D’Souza, D. Zack Brodtman, Simone Sidoli, Bill Diplas, Manisha Jalan, Nancy Y. Lee, Alban Ordureau, Benjamin Izar, Ashley M. Laughney, Simon Powell, Enrico Gratton, Stefano Santaguida, John Maciejowski, Peter Ly, Thomas M. Jeitner, and Samuel F. Bakhoum. Micronuclear collapse from oxidative damage. Science, Aug 2024. URL: https://doi.org/10.1126/science.adj8691, doi:10.1126/science.adj8691. This article has 75 citations and is from a highest quality peer-reviewed journal.
(bona2024anewmicroscopy pages 1-2): Melody Di Bona and Samuel F. Bakhoum. A new microscopy pipeline for studying the initial stages of nuclear and micronuclear rupture and repair. Frontiers in Cell and Developmental Biology, Sep 2024. URL: https://doi.org/10.3389/fcell.2024.1475095, doi:10.3389/fcell.2024.1475095. This article has 1 citations.
(caravia2022lossoffunction pages 9-11): Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, and Eric N. Olson. Loss of function of the nuclear envelope protein lemd2 causes dna damage–dependent cardiomyopathy. The Journal of Clinical Investigation, Nov 2022. URL: https://doi.org/10.1172/jci158897, doi:10.1172/jci158897. This article has 23 citations.
(rose2024theexpressionand pages 1-2): Maddison Rose, Joshua T. Burgess, Chee Man Cheong, Mark N. Adams, Parastoo Shahrouzi, Kenneth J. O’Byrne, Derek J. Richard, and Emma Bolderson. The expression and role of the lem-d proteins ankle2, emerin, lemd2, and tmpo in triple-negative breast cancer cell growth. Frontiers in Oncology, Apr 2024. URL: https://doi.org/10.3389/fonc.2024.1222698, doi:10.3389/fonc.2024.1222698. This article has 1 citations.
(ravera2025cardiovascularinvolvementin pages 8-9): Francesco Ravera, Veronica Dusi, Pier Paolo Bocchino, Giulia Gobello, Giuseppe Giannino, Daniele Melis, Giulia Margherita Brach Del Prever, Filippo Angelini, Andrea Saglietto, Carla Giustetto, Guglielmo Gallone, Stefano Pidello, Margherita Cannillo, Marco Matteo Cingolani, Silvia Deaglio, Walter Grosso Marra, Gaetano Maria De Ferrari, and Claudia Raineri. Cardiovascular involvement in syne variants: a case series and narrative review. Cardiogenetics, 15:2, Jan 2025. URL: https://doi.org/10.3390/cardiogenetics15010002, doi:10.3390/cardiogenetics15010002. This article has 3 citations.
(caravia2022lossoffunction pages 7-9): Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, and Eric N. Olson. Loss of function of the nuclear envelope protein lemd2 causes dna damage–dependent cardiomyopathy. The Journal of Clinical Investigation, Nov 2022. URL: https://doi.org/10.1172/jci158897, doi:10.1172/jci158897. This article has 23 citations.
(caravia2022lossoffunction pages 6-7): Xurde M. Caravia, Andres Ramirez-Martinez, Peiheng Gan, Feng Wang, John R. McAnally, Lin Xu, Rhonda Bassel-Duby, Ning Liu, and Eric N. Olson. Loss of function of the nuclear envelope protein lemd2 causes dna damage–dependent cardiomyopathy. The Journal of Clinical Investigation, Nov 2022. URL: https://doi.org/10.1172/jci158897, doi:10.1172/jci158897. This article has 23 citations.
(bona2024micronuclearcollapsefrom media c1457801): Melody Di Bona, Yanyang Chen, Albert S. Agustinus, Alice Mazzagatti, Mercedes A. Duran, Matthew Deyell, Daniel Bronder, James Hickling, Christy Hong, Lorenzo Scipioni, Giulia Tedeschi, Sara Martin, Jun Li, Aušrinė Ruzgaitė, Nadeem Riaz, Parin Shah, Edridge K. D’Souza, D. Zack Brodtman, Simone Sidoli, Bill Diplas, Manisha Jalan, Nancy Y. Lee, Alban Ordureau, Benjamin Izar, Ashley M. Laughney, Simon Powell, Enrico Gratton, Stefano Santaguida, John Maciejowski, Peter Ly, Thomas M. Jeitner, and Samuel F. Bakhoum. Micronuclear collapse from oxidative damage. Science, Aug 2024. URL: https://doi.org/10.1126/science.adj8691, doi:10.1126/science.adj8691. This article has 75 citations and is from a highest quality peer-reviewed journal.
(barger2023nuclearenvelopeassembly pages 25-27): Sarah R. Barger, Lauren Penfield, and Shirin Bahmanyar. Nuclear envelope assembly relies on chmp-7 in the absence of baf–lem-mediated hole closure. Journal of Cell Science, Nov 2023. URL: https://doi.org/10.1242/jcs.261385, doi:10.1242/jcs.261385. This article has 10 citations and is from a domain leading peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Citations

nair2025nuclearenvelopeand pages 8-10
caravia2022lossoffunction pages 1-2
keeley2024nuclearanddegradative pages 3-4
barger2023nuclearenvelopeassembly pages 12-14
bona2024micronuclearcollapsefrom pages 1-3
bona2024anewmicroscopy pages 1-2
rose2024theexpressionand pages 1-2
lipov2023exploringthecomplex pages 3-4
caravia2022lossoffunction pages 9-11
ravera2025cardiovascularinvolvementin pages 8-9
johnson2020discoveringhowinner pages 22-27
caravia2022lossoffunction pages 7-9
barger2023nuclearenvelopeassembly pages 25-27
borah2022thelemescrttoolkit pages 3-4
johnson2020discoveringhowinner pages 13-16
johnson2020discoveringhowinner pages 35-39
borah2022thelemescrttoolkit pages 1-3
caravia2022lossoffunction pages 6-7
https://doi.org/10.1172/jci158897;
https://doi.org/10.1080/19491034.2024.2449520
https://doi.org/10.1080/19491034.2024.2349085
https://doi.org/10.3389/fcell.2022.989217
https://doi.org/10.1080/19491034.2024.2449520;
https://doi.org/10.3389/fcell.2022.989217;
https://doi.org/10.1242/jcs.261385
https://doi.org/10.1126/science.adj8691
https://doi.org/10.3389/fcell.2024.1475095
https://doi.org/10.1172/jci158897
https://doi.org/10.3389/fonc.2024.1222698
https://doi.org/10.1038/s44161-023-00346-3
https://doi.org/10.1172/jci158897,
https://doi.org/10.1080/19491034.2024.2449520,
https://doi.org/10.1080/19491034.2024.2349085,
https://doi.org/10.1038/s44161-023-00346-3,
https://doi.org/10.3389/fcell.2022.989217,
https://doi.org/10.1242/jcs.261385,
https://doi.org/10.1126/science.adj8691,
https://doi.org/10.3389/fcell.2024.1475095,
https://doi.org/10.3389/fonc.2024.1222698,
https://doi.org/10.3390/cardiogenetics15010002,

Perplexity

(LEMD2-deep-research-perplexity-lite.md)

**Molecular Function** Perplexity sonar-pro 10 citations 2025-11-01T14:25:13.038029

The LEMD2 gene encodes a transmembrane protein of the inner nuclear membrane (INM) that is essential for nuclear envelope integrity, chromatin organization, and cardiac function in humans[3][7][8].

Molecular Function
- LEMD2 is a nuclear lamina-associated protein involved in the organization and maintenance of the nuclear envelope (NE), especially during NE reformation after mitosis[3][7].
- It acts as a transmembrane adapter for the ESCRT (endosomal sorting complexes required for transport) machinery, recruiting proteins such as CHMP7, IST1/CHMP8, and CHMP2A to facilitate NE closure during cell division[3][4].
- LEMD2 interacts with DNA-binding proteins, notably lamins and barrier-to-autointegration factor (BAF), mediating the connection between chromatin and the NE[1][2][3][4].

Biological Processes
- Nuclear envelope organization and repair: LEMD2 is critical for detecting and repairing nuclear envelope ruptures, both during mitotic exit and interphase, by recruiting ESCRT-III components[3][4].
- Chromatin organization: It helps organize heterochromatin at the NE, influencing gene expression and maintaining genome stability[1][2][3].
- Cell signaling and differentiation: LEMD2 regulates signaling pathways such as MAPK/ERK and AKT, and is required for myoblast differentiation and cardiac homeostasis[3][4][9].
- Embryonic development: LEMD2 is essential for embryogenesis, particularly for proper heart development[1][2][3].

Cellular Localization
- LEMD2 is localized to the inner nuclear membrane (INM), where it associates with the nuclear lamina and chromatin[1][2][3][7][8].

Protein Domains
- Contains a highly conserved LEM domain, which mediates interactions with BAF and lamins[1][2][3][7].
- Has two transmembrane domains anchoring it to the INM[1][2][3][7].

Known Interactions
- Lamins (A/C): Structural proteins of the nuclear lamina[1][2][3].
- BAF (Barrier-to-autointegration factor): DNA-binding protein involved in chromatin organization[1][2][3][4].
- ESCRT-III components (CHMP7, IST1/CHMP8, CHMP2A): Involved in NE reformation and repair[3][4].
- Signaling molecules: Modulates ERK and AKT pathways, especially in muscle and cardiac cells[3][4].

Disease Associations
- Cardiac disease: Homozygous missense mutations in LEMD2 (e.g., c.T38>G, p.L13R in the LEM domain) are linked to arrhythmic cardiomyopathy, cataracts, and sudden death in humans[1][2][3][6].
- Dilated cardiomyopathy and cardiac fibrosis: Loss of LEMD2 function in mouse models leads to severe cardiac defects, nuclear envelope deformations, DNA damage, and apoptosis via p53 activation[1][2].
- Nuclear envelopathies: Mutations cause a spectrum of nuclear envelope disorders, with variable prognosis depending on the mutation[6].
- Cataract 46: Mutations in LEMD2 are associated with this specific form of inherited cataract[3].

Recent Developments (2023-2024)
- Studies have reinforced the role of LEMD2 in genome stability and cardiac function, with gene therapy approaches showing rescue of cardiac defects in animal models[1].
- Transcriptomic analyses reveal that LEMD2 deficiency leads to widespread changes in gene expression, activation of p53-dependent DNA damage response, and apoptosis in cardiomyocytes[2].
- LEMD2’s role in nuclear envelope surveillance and ESCRT-mediated repair is increasingly recognized as central to maintaining cellular homeostasis, especially under mechanical stress[3][4].

Summary Table: LEMD2 Key Features

Feature	Details
Molecular Function	NE integrity, chromatin organization, ESCRT-mediated NE repair, signaling regulation
Biological Processes	NE organization, chromatin stabilization, cardiac and muscle differentiation, apoptosis
Cellular Localization	Inner nuclear membrane (INM)
Protein Domains	LEM domain, 2 transmembrane domains
Interactions	Lamins, BAF, ESCRT-III proteins, ERK/AKT signaling molecules
Disease Associations	Arrhythmic cardiomyopathy, cataract 46, nuclear envelopathies, cardiac fibrosis

Authoritative Sources:
- JCI (2023): [https://www.jci.org/articles/view/158897][1] (Published 2023)
- PMC (2023): [https://pmc.ncbi.nlm.nih.gov/articles/PMC9663152/][2] (Published 2023)
- GeneCards (2024): [https://www.genecards.org/cgi-bin/carddisp.pl?gene=LEMD2][3] (Accessed 2024)
- UniProt (2024): [https://www.uniprot.org/uniprotkb/Q8NC56/entry][7] (Accessed 2024)
- NCBI Gene (2024): [https://www.ncbi.nlm.nih.gov/gene/221496][8] (Accessed 2024)
- NIH PMC (2019): [https://pmc.ncbi.nlm.nih.gov/articles/PMC6451726/][6] (Published 2019)

LEMD2 is a multifunctional nuclear envelope protein with critical roles in genome stability, cardiac function, and nuclear envelope repair, and its dysfunction is associated with severe human disease phenotypes[1][2][3][6].

Citations

https://www.jci.org/articles/view/158897
https://pmc.ncbi.nlm.nih.gov/articles/PMC9663152/
https://www.genecards.org/cgi-bin/carddisp.pl?gene=LEMD2
https://maayanlab.cloud/Harmonizome/gene/LEMD2
https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=DetailsSearch&Term=221496
https://pmc.ncbi.nlm.nih.gov/articles/PMC6451726/
https://www.uniprot.org/uniprotkb/Q8NC56/entry
https://www.ncbi.nlm.nih.gov/gene/221496
https://www.alliancegenome.org/gene/HGNC:21244
https://www.proteinatlas.org/ENSG00000161904-LEMD2

📄 View Raw YAML

id: Q8NC56
gene_symbol: LEMD2
product_type: PROTEIN
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: 'LEM domain-containing protein 2, transmembrane protein of inner nuclear
  membrane (INM) essential for nuclear envelope integrity, chromatin organization,
  and cardiac function. Contains highly conserved LEM domain mediating interactions
  with BAF (barrier-to-autointegration factor) and lamins, plus two transmembrane
  domains anchoring it to INM. Acts as transmembrane adapter for ESCRT (endosomal
  sorting complexes required for transport) machinery, recruiting proteins CHMP7,
  IST1/CHMP8, and CHMP2A to facilitate nuclear envelope closure during cell division
  and repair. Critical for detecting and repairing nuclear envelope ruptures both
  during mitotic exit and interphase by recruiting ESCRT-III components. Interacts
  with DNA-binding proteins (lamins and BAF), mediating connection between chromatin
  and nuclear envelope. Helps organize heterochromatin at NE, influencing gene expression
  and maintaining genome stability. Regulates signaling pathways MAPK/ERK and AKT,
  required for myoblast differentiation and cardiac homeostasis. Essential for embryogenesis,
  particularly proper heart development. Localized to inner nuclear membrane where
  it associates with nuclear lamina and chromatin. Known interactions: Lamins A/C
  (nuclear lamina structural proteins), BAF (DNA-binding protein for chromatin organization),
  ESCRT-III components (NE reformation and repair), signaling molecules (modulates
  ERK and AKT pathways in muscle/cardiac cells). Homozygous missense mutations (e.g.
  c.T38>G, p.L13R in LEM domain) linked to arrhythmic cardiomyopathy, cataracts, and
  sudden death. Loss of function causes severe cardiac defects, nuclear envelope deformations,
  DNA damage, and apoptosis via p53 activation. LEMD2 deficiency leads to widespread
  gene expression changes, activation of p53-dependent DNA damage response, and cardiomyocyte
  apoptosis. Mutations cause dilated cardiomyopathy, cardiac fibrosis, and cataract
  46. Role in nuclear envelope surveillance and ESCRT-mediated repair is central to
  maintaining cellular homeostasis, especially under mechanical stress. Gene therapy
  approaches show rescue of cardiac defects in animal models.'
existing_annotations:
- term:
    id: GO:0071763
    label: nuclear membrane organization
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: Nuclear membrane organization - core function. LEMD2/LEM2 closes
      nuclear envelope holes around spindle microtubules together with CHMP7,
      and its C-terminal winged-helix domain copolymerizes with CHMP7 into
      50-100 nm rings that restrict diffusion at NE holes.
    action: ACCEPT
    reason: Primary process supported by multiple mechanistic studies.
    supported_by:
    - reference_id: file:human/LEMD2/LEMD2-deep-research-perplexity-lite.md
      supporting_text: See deep research file for comprehensive analysis
    - reference_id: file:human/LEMD2/LEMD2-deep-research-falcon.md
      supporting_text: 'LEMD2 is described as a ubiquitously expressed INM
        protein with a conserved N-terminal LEM domain and two transmembrane
        segments, localizing at the nuclear periphery. Its LEM domain enables
        association with DNA-associated proteins including lamins and BAF,
        supporting a chromatin–nuclear envelope tethering function.'
    - reference_id: PMID:37795681
      supporting_text: The LEM-domain protein LEMD2 contributes to NE sealing
        through its C-terminal winged helix (WH) domain, which directly binds
        and activates the conserved endosomal sorting complex required for
        transport (ESCRT)-II/ESCRT-III hybrid protein CHMP7
- term:
    id: GO:0005637
    label: nuclear inner membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: Nuclear inner membrane - specific INM protein.
    action: ACCEPT
    reason: Core localization.
- term:
    id: GO:0034399
    label: nuclear periphery
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: Nuclear periphery - INM localization.
    action: ACCEPT
    reason: Core localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005637
    label: nuclear inner membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: Nuclear inner membrane - specific INM protein.
    action: ACCEPT
    reason: Core localization.
- term:
    id: GO:0005819
    label: spindle
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: Spindle - NE reformation during mitosis.
    action: KEEP_AS_NON_CORE
    reason: Cell division context.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28514442
  review:
    summary: Protein binding from HTP interactome study - generic term per
      CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule
      adaptor activity in core_functions) capture the actual scaffold/adapter role.
    action: MARK_AS_OVER_ANNOTATED
    reason: Per CLAUDE.md, avoid the generic protein-binding term when more
      specific MFs are available; PR #758 review feedback.
    supported_by:
    - reference_id: PMID:28514442
      supporting_text: Architecture of the human interactome defines protein
        communities and disease networks.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  review:
    summary: Protein binding from HTP interactome study - generic term per
      CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule
      adaptor activity in core_functions) capture the actual scaffold/adapter role.
    action: MARK_AS_OVER_ANNOTATED
    reason: Per CLAUDE.md, avoid the generic protein-binding term when more
      specific MFs are available; PR #758 review feedback.
    supported_by:
    - reference_id: PMID:33961781
      supporting_text: 2021 May 6. Dual proteome-scale networks reveal
        cell-specific remodeling of the human interactome.
- term:
    id: GO:0022008
    label: neurogenesis
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Neurogenesis - developmental role.
    action: KEEP_AS_NON_CORE
    reason: Broad developmental process.
- term:
    id: GO:0031965
    label: nuclear membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: Nuclear membrane - general NE localization.
    action: ACCEPT
    reason: Core localization.
- term:
    id: GO:0035914
    label: skeletal muscle cell differentiation
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: Skeletal muscle cell differentiation - myoblast differentiation.
    action: ACCEPT
    reason: Differentiation role.
- term:
    id: GO:0043409
    label: negative regulation of MAPK cascade
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Negative regulation of MAPK cascade - regulates ERK pathway.
    action: ACCEPT
    reason: Signaling regulation.
- term:
    id: GO:0051898
    label: negative regulation of phosphatidylinositol 3-kinase/protein kinase B
      signal transduction
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Negative regulation of PI3K/AKT signaling.
    action: ACCEPT
    reason: Signaling regulation.
- term:
    id: GO:0060914
    label: heart formation
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Heart formation - essential for cardiac development. Knockin mice
      with the human p.L13R LEM-domain mutation develop dilated cardiomyopathy
      and cardiac fibrosis; cardiomyocyte-specific Lemd2 KO mice die in the
      neonatal period from cardiac abnormalities.
    action: ACCEPT
    reason: Core cardiac role supported by KI and conditional KO mouse models.
    supported_by:
    - reference_id: PMID:36377660
      supporting_text: We generated knockin (KI) mice carrying the human c.T38>G
        Lemd2 mutation, which causes a missense amino acid exchange (p.L13>R) in
        the LEM domain of the protein. These mice represent a preclinical model
        that phenocopies the human disease, as they developed severe dilated
        cardiomyopathy and cardiac fibrosis leading to premature death.
    - reference_id: file:human/LEMD2/LEMD2-deep-research-falcon.md
      supporting_text: 'A 2022 Journal of Clinical Investigation study created a
        knock-in mouse carrying the human disease allele c.T38>G (p.L13R) and
        showed severe dilated cardiomyopathy and fibrosis. Importantly,
        cardiomyocyte-specific AAV-mediated Lemd2 gene therapy rescued cardiac
        function in KI/KI mice.'
- term:
    id: GO:0031965
    label: nuclear membrane
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  review:
    summary: Nuclear membrane - general NE localization.
    action: ACCEPT
    reason: Core localization.
- term:
    id: GO:0000785
    label: chromatin
  evidence_type: IDA
  original_reference_id: PMID:28242692
  review:
    summary: Chromatin - organizes heterochromatin at NE. Cardiomyocyte-specific
      loss of LEMD2 disorganizes the transcriptionally silent heterochromatin
      associated with the nuclear envelope.
    action: ACCEPT
    reason: Core function supported by mouse models.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
    - reference_id: PMID:36377660
      supporting_text: At the cellular level, KI/KI cardiomyocytes exhibited
        disorganization of the transcriptionally silent heterochromatin
        associated with the nuclear envelope.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IDA
  original_reference_id: PMID:28242692
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: PMID:28242692
  review:
    summary: ER - INM is continuous with ER but distinct.
    action: KEEP_AS_NON_CORE
    reason: Related but distinct compartment.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
- term:
    id: GO:0016020
    label: membrane
  evidence_type: TAS
  original_reference_id: PMID:28242692
  review:
    summary: Membrane - transmembrane protein.
    action: ACCEPT
    reason: General membrane.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
- term:
    id: GO:0071168
    label: protein localization to chromatin
  evidence_type: IMP
  original_reference_id: PMID:28242692
  review:
    summary: |
      Protein localization to chromatin annotation — the original PMID:28242692
      reference is about ESCRT-mediated NE closure, NOT chromatin tethering
      (PR #758 review feedback). The biologically valid support for chromatin-
      tethering comes from LEMD2's LEM-domain interactions with BAF and lamins
      (the chromatin–NE tethering axis), captured separately by GO:0000785
      chromatin and supported by PMID:36377660 below. Annotation kept as
      KEEP_AS_NON_CORE pending re-citation; the original PMID:28242692
      supporting_text does not address chromatin-localization mechanism.
    action: KEEP_AS_NON_CORE
    reason: |
      The annotation is biologically plausible (via LEM-domain-BAF tethering),
      but the original PMID:28242692 reference does not directly establish
      chromatin localization; downgraded from ACCEPT pending a primary
      reference that directly demonstrates LEMD2-mediated chromatin protein
      localization.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28242692
  review:
    summary: Protein binding from HTP interactome study - generic term per
      CLAUDE.md guidance, more informative MFs (GO:0030674 protein-macromolecule
      adaptor activity in core_functions) capture the actual scaffold/adapter role.
    action: MARK_AS_OVER_ANNOTATED
    reason: Per CLAUDE.md, avoid the generic protein-binding term when more
      specific MFs are available; PR #758 review feedback.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
- term:
    id: GO:0005637
    label: nuclear inner membrane
  evidence_type: TAS
  original_reference_id: PMID:28242692
  review:
    summary: Nuclear inner membrane - specific INM protein.
    action: ACCEPT
    reason: Core localization.
    supported_by:
    - reference_id: PMID:28242692
      supporting_text: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope
        closure in fission yeast and human cells.
- term:
    id: GO:0006998
    label: nuclear envelope organization
  evidence_type: IMP
  original_reference_id: PMID:17097643
  review:
    summary: Nuclear envelope organization - primary function. LEMD2/LEM2
      together with CHMP7 seals NE holes around spindle microtubules during
      mitotic exit; redundant with BAF-LEM-mediated hole closure.
    action: ACCEPT
    reason: Core process supported by mechanistic studies in human cells and
      C. elegans.
    supported_by:
    - reference_id: PMID:17097643
      supporting_text: Epub 2006 Nov 3. The inner nuclear membrane protein Lem2
        is critical for normal nuclear envelope morphology.
    - reference_id: PMID:37795681
      supporting_text: The LAP2-emerin-MAN1 (LEM)-domain protein LEMD2 and
        ESCRT-II/III hybrid protein CHMP7 close NE holes surrounding spindle
        microtubules (MTs).
    - reference_id: file:human/LEMD2/LEMD2-deep-research-falcon.md
      supporting_text: 'In nuclear-envelope maintenance, CHMP7 together with INM
        LEMD2 is implicated in sealing small nuclear-envelope holes, whereas
        repair of larger ruptures can depend more strongly on BAF-mediated
        mechanisms.'
- term:
    id: GO:0016020
    label: membrane
  evidence_type: HDA
  original_reference_id: PMID:19946888
  review:
    summary: Membrane - transmembrane protein.
    action: ACCEPT
    reason: General membrane.
    supported_by:
    - reference_id: PMID:19946888
      supporting_text: Defining the membrane proteome of NK cells.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668335
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668389
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668395
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668398
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668405
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668415
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9668419
  review:
    summary: Nuclear envelope - core localization.
    action: ACCEPT
    reason: Primary localization.
- term:
    id: GO:0005637
    label: nuclear inner membrane
  evidence_type: IDA
  original_reference_id: PMID:16339967
  review:
    summary: Nuclear inner membrane - specific INM protein.
    action: ACCEPT
    reason: Core localization.
    supported_by:
    - reference_id: PMID:16339967
      supporting_text: LEM2 is a novel MAN1-related inner nuclear membrane
        protein associated with A-type lamins.
- term:
    id: GO:0035914
    label: skeletal muscle cell differentiation
  evidence_type: IGI
  original_reference_id: PMID:19720741
  review:
    summary: Skeletal muscle cell differentiation - myoblast differentiation.
    action: ACCEPT
    reason: Differentiation role.
    supported_by:
    - reference_id: PMID:19720741
      supporting_text: Aug 31. Overlapping functions of nuclear envelope
        proteins NET25 (Lem2) and emerin in regulation of extracellular
        signal-regulated kinase signaling in myoblast differentiation.
- term:
    id: GO:0006325
    label: chromatin organization
  evidence_type: NAS
  review:
    summary: Added to align core_functions with existing annotations.
    action: NEW
    reason: Core function term not present in existing_annotations.
    supported_by:
    - reference_id: file:human/LEMD2/LEMD2-uniprot.txt
      supporting_text: LEMD2 is INM protein with LEM domain. Essential for NE
        integrity and repair via ESCRT. Mutations cause arrhythmic
        cardiomyopathy.
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular
    Location vocabulary mapping, accompanied by conservative changes to GO terms
    applied by UniProt.
  findings: []
- id: GO_REF:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data
    to orthologs using Ensembl Compara.
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods.
  findings: []
- id: PMID:16339967
  title: LEM2 is a novel MAN1-related inner nuclear membrane protein associated
    with A-type lamins.
  findings: []
- id: PMID:17097643
  title: The inner nuclear membrane protein Lem2 is critical for normal nuclear
    envelope morphology.
  findings:
  - statement: LEM2 is required for normal nuclear envelope morphology.
    supporting_text: The inner nuclear membrane protein Lem2 is critical for
      normal nuclear envelope morphology.
    reference_section_type: TITLE
- id: PMID:36377660
  title: Loss of function of the nuclear envelope protein LEMD2 causes DNA
    damage-dependent cardiomyopathy.
  findings:
  - statement: Knockin mice carrying the human LEMD2 c.T38>G (p.L13R) LEM-domain
      mutation phenocopy human disease, developing severe dilated cardiomyopathy
      and cardiac fibrosis; cardiomyocyte-specific Lemd2 KO mice die shortly
      after birth from cardiac abnormalities with extensive DNA damage and p53
      activation, and AAV-mediated cardiomyocyte-specific Lemd2 delivery rescues
      cardiac function.
    supporting_text: We generated knockin (KI) mice carrying the human c.T38>G
      Lemd2 mutation, which causes a missense amino acid exchange (p.L13>R) in
      the LEM domain of the protein. These mice represent a preclinical model
      that phenocopies the human disease, as they developed severe dilated
      cardiomyopathy and cardiac fibrosis leading to premature death. At the
      cellular level, KI/KI cardiomyocytes exhibited disorganization of the
      transcriptionally silent heterochromatin associated with the nuclear
      envelope. Moreover, mice with cardiac-specific deletion of Lemd2 also died
      shortly after birth due to heart abnormalities. Cardiomyocytes lacking
      Lemd2 displayed nuclear envelope deformations and extensive DNA damage and
      apoptosis linked to p53 activation. Importantly, cardiomyocyte-specific
      Lemd2 gene therapy via adeno-associated virus rescued cardiac function in
      KI/KI mice.
    reference_section_type: ABSTRACT
  - statement: LEMD2 is an INM protein with a LEM domain and two transmembrane
      domains that mediates interaction between chromatin and the NE via
      association with lamins and BAF.
    supporting_text: LEM domain–containing protein 2 (LEMD2), which is expressed
      ubiquitously, is characterized by the presence of the LEM domain and 2
      transmembrane domains. A series of in vitro studies revealed its ability
      to associate with DNA-binding proteins such as lamins and
      barrier-to-autointegration factor (BAF), which implicates LEMD2 as a
      mediator of the interaction between chromatin and the NE
    reference_section_type: INTRODUCTION
- id: PMID:37795681
  title: Nuclear envelope assembly relies on CHMP-7 in the absence of
    BAF-LEM-mediated hole closure.
  findings:
  - statement: LEMD2 contributes to NE sealing through its C-terminal winged
      helix (WH) domain, which directly binds and activates CHMP7; the WH of
      LEMD2 copolymerizes with CHMP7 to form 50-100 nm rings on the cytosolic
      surface of NE holes to restrict diffusion. The WH domain of LEM-2
      (C. elegans LEMD2 homolog) recruits CHMP-7 to the NE; LEM-2-CHMP-7
      function is essential for NE assembly when BAF-LEM binding is compromised.
    supporting_text: The LEM-domain protein LEMD2 contributes to NE sealing
      through its C-terminal winged helix (WH) domain, which directly binds and
      activates the conserved endosomal sorting complex required for transport
      (ESCRT)-II/ESCRT-III hybrid protein CHMP7 (Gatta et al., 2021; Gu et al.,
      2017; von Appen et al., 2020). The WH of LEMD2 copolymerizes with CHMP7
      to form 50–100 nm rings in vitro and it is thought that the assembly of
      these rings on the cytosolic surface of NE holes restricts the diffusion
      of macromolecules
    reference_section_type: INTRODUCTION
- id: PMID:39208110
  title: Micronuclear collapse from oxidative damage.
  findings:
  - statement: Mitochondria-derived ROS disrupt micronuclear integrity through
      a pathological axis in which ROS-induced cysteine oxidation stimulates
      CHMP7 oligomerization and aberrant binding to LEMD2, disrupting
      micronuclear envelopes and engendering chromosome shattering. This axis
      mediates micronuclear disintegrity under hypoxic conditions, linking
      tumor microenvironment stress to aberrant engagement of the LEMD2-CHMP7
      module.
    supporting_text: ROS-induced cysteine oxidation stimulated CHMP7
      oligomerization and binding to the nuclear membrane protein LEMD2,
      disrupting micronuclear envelopes. Furthermore, this ROS-CHMP7
      pathological axis engendered chromosome shattering known to result from
      micronuclear rupture. It also mediated micronuclear disintegrity under
      hypoxic conditions, linking tumor microenvironment
    reference_section_type: ABSTRACT
  - statement: The ESCRT-III complex mediates nuclear envelope repair by
      assembling through binding to LEMD2 and CHMP7 scaffolds at nuclear
      membrane rupture sites.
    supporting_text: The endosomal sorting complex required for transport III
      (ESCRT-III) complex is a key player in mediating nuclear envelope repair,
      and it assembles through binding to LEM domain nuclear envelope protein 2
      (LEMD2) and charged multivesicular body protein 7 (CHMP7) scaffolds at the
      nuclear membrane rupture sites
    reference_section_type: INTRODUCTION
- id: file:human/LEMD2/LEMD2-deep-research-falcon.md
  title: Deep research on LEMD2 function (falcon)
  findings:
  - statement: LEMD2/LEM2 acts as a chromatin-lamina-ESCRT integrator at the
      inner nuclear membrane; its N-terminal LEM domain binds BAF and lamins,
      a low-complexity region undergoes liquid-liquid phase separation at
      spindle-associated membrane gaps, and the C-terminal winged-helix/MSC
      domain binds and activates CHMP7 to nucleate ESCRT-III-mediated NE
      sealing. The CHMP7/LEMD2 module preferentially seals small NE holes
      (<100 nm), while BAF-driven mechanisms dominate at larger ruptures.
    supporting_text: 'Mechanistically, LEM2/LEMD2 can recruit/activate CHMP7
      via a C-terminal WH/MSC domain; CHMP7 then nucleates downstream ESCRT-III
      assembly for membrane sealing.'
    reference_section_type: OTHER
- id: PMID:19720741
  title: Overlapping functions of nuclear envelope proteins NET25 (Lem2) and
    emerin in regulation of extracellular signal-regulated kinase signaling in
    myoblast differentiation.
  findings: []
- id: PMID:19946888
  title: Defining the membrane proteome of NK cells.
  findings: []
- id: PMID:28242692
  title: LEM2 recruits CHMP7 for ESCRT-mediated nuclear envelope closure in
    fission yeast and human cells.
  findings: []
- id: PMID:28514442
  title: Architecture of the human interactome defines protein communities and
    disease networks.
  findings: []
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the
    human interactome.
  findings: []
- id: Reactome:R-HSA-9668335
  title: CHMP7 binds LEMD2
  findings: []
- id: Reactome:R-HSA-9668389
  title: VPS4 binds ESCRT-III assemblies at nuclear envelope (NE) fenestrations
  findings: []
- id: Reactome:R-HSA-9668395
  title: CHMP7 binds CC2D1B
  findings: []
- id: Reactome:R-HSA-9668398
  title: CHMP7 binds CHMP4B, which recruits other subunits of the ESCRT-III
    complex
  findings: []
- id: Reactome:R-HSA-9668405
  title: SPAST (spastin) binds the IST1 subunit of ESCRT-III at the sites of
    microtubule attachment to chromatin
  findings: []
- id: Reactome:R-HSA-9668415
  title: VPS4 mediates disassembly of ESCRTIII subunits to promote sealing of
    holes in the nuclear envelope
  findings: []
- id: Reactome:R-HSA-9668419
  title: SPAST (spastin) mediates the severing of microtubules at chromosome
    attachment sites
  findings: []
- id: file:human/LEMD2/LEMD2-deep-research-perplexity-lite.md
  title: Deep research on LEMD2 function
  findings: []
aliases:
- LEM domain-containing protein 2
- Inner nuclear membrane protein Man1
core_functions:
- molecular_function:
    id: GO:0030674
    label: protein-macromolecule adaptor activity
  description: |
    ESCRT adapter at inner nuclear membrane that binds lamins, BAF, and
    CHMP7/IST1/CHMP2A. Mediates chromatin-nuclear envelope connection and
    recruits ESCRT-III machinery for nuclear envelope repair and closure
    during cell division. The molecular_function GO:0030674 (protein-
    macromolecule adaptor activity) replaces the previously-listed generic
    GO:0005515 (protein binding) per PR #758 review feedback and CLAUDE.md
    guidance against the generic protein-binding term.
  locations:
  - id: GO:0005637
    label: nuclear inner membrane
  directly_involved_in:
  - id: GO:0006998
    label: nuclear envelope organization
  - id: GO:0006325
    label: chromatin organization
  supported_by:
  - reference_id: file:human/LEMD2/LEMD2-uniprot.txt
    supporting_text: LEMD2 is INM protein with LEM domain. Essential for NE
      integrity and repair via ESCRT. Mutations cause arrhythmic cardiomyopathy.
status: COMPLETE

LEMD2

Gene Description

Existing Annotations Review

Core Functions

References

Deep Research

Falcon

Research Report: Human LEMD2 (UniProt Q8NC56) — functional annotation, pathways, and disease relevance

0) Identity verification (critical)

1) Key concepts and definitions (current understanding)

1.1 LEM-domain proteins

1.2 LEMD2 (LEM2) core cell-biological role

1.3 ESCRT-III and the LEMD2–CHMP7 “compartmentalization sensor” module

2) Molecular functions, domains, and localization (functional annotation)

2.1 Subcellular localization

2.2 Domain-to-function mapping

2.3 Mechanistic model (mitosis and interphase)

3) Recent developments and latest research (prioritizing 2023–2024)

3.1 2023: Redundancy between BAF–LEM and LEM2–CHMP7 pathways in NE sealing

3.2 2024: Direct connection of LEMD2–CHMP7 to micronuclear collapse under oxidative stress (Science)

3.3 2024: Experimental/technical real-time interrogation of LEMD2–CHMP7 recruitment at ruptures

3.4 2024: Review synthesis (neurodegeneration angle)

4) Current applications and real-world implementations

4.1 Preclinical gene therapy for LEMD2-associated cardiomyopathy (proof of concept)

4.2 Oncology: LEMD2 as a candidate cancer vulnerability/biomarker target class (preclinical)

4.3 Micronuclei rupture assays and repair-pathway profiling

5) Expert opinions and analysis (authoritative synthesis)

5.1 Functional partitioning: small-hole sealing vs large-rupture plugging

5.2 Disease mechanism framing

5.3 Cancer relevance: “too much” versus “too little” repair

6) Key statistics and quantitative data (recent and foundational)

6.1 Human genetics (from 2023 synthesis)

6.2 Preclinical therapy parameters (JCI 2022)

6.3 Survival/lethality in mouse models (JCI 2022)

6.4 Variant impact on expression and conduction phenotypes

6.5 Mechanistic size/geometry constraints

7) Visual evidence: ROS–CHMP7–LEMD2 model

8) Limitations and evidence gaps (within retrieved corpus)

References (URLs, dates)

Artifacts

Citations

Perplexity

Citations

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