AHDC1 encodes Gibbin, a 1,603-residue nuclear protein containing annotated AT-hook motifs and conserved regions including DUF4683. It associates with transcriptional regulators and chromatin and helps establish developmental gene-expression programs. In retinoic-acid/BMP4-induced human embryonic stem-cell differentiation, AHDC1 occupies active promoters and enhancers and supports GATA3-dependent transcription. Its loss alters local DNA methylation, CTCF occupancy and chromatin contacts, with impaired mesoderm maturation and non-cell-autonomous defects in epidermal differentiation. The molecular connection between AHDC1 and DNA methyltransferase activity remains unresolved, as do its intrinsic DNA-sequence preferences and any direct loop-bridging activity. Heterozygous pathogenic variants cause Xia-Gibbs syndrome, characterized by developmental and speech delay, intellectual disability, hypotonia and variable additional features. Patient-derived truncations can alter intranuclear localization; the relative contributions of reduced dosage and variant-specific effects remain under investigation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0001707 mesoderm formation | IDA PMID:35585237 Gibbin mesodermal regulation patterns epithelial development... | KEEP AS NON CORE | Summary: AHDC1 supports mesoderm development in differentiating human stem cells. Reason: PMID:35585237 combines AHDC1 occupancy at lineage regulatory elements, altered transcription after knockout, and depletion of PDGFRA-positive mesodermal cells during RA/BMP4 differentiation. AHDC1 participates through regulation of the developmental program; the annotation is retained as a developmental consequence of its chromatin-associated transcriptional role. The seeded experimental evidence code is preserved. Supporting Evidence: PMID:35585237 Single cell RNA sequencing (scRNA-seq) confirmed that mesodermal (PDGFRA+) cells as well as individual gene markers for that cluster were severely diminished in the GKO PMID:35585237 By RNA-seq, expression of ~1,100 transcripts were significantly altered in the Gibbin KO (GKO) compared to wildtype (WT) |
| GO:0001707 mesoderm formation | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Mouse ortholog evidence supports conserved developmental involvement. Reason: The Compara sources identify mouse Ahdc1. The recovered MGI snapshot links mesoderm formation to experimental PMID:35585237, which contains mouse developmental perturbations and separate human stem-cell experiments. The clearest cell-lineage assay is the human PDGFRA-positive-cell analysis; it independently supports the target assertion. The transfer is biologically consistent, and its developmental scope is retained as non-core without treating a shared reference as circular evidence. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: UniProtKB:Q6PAL7 Β· mouse Ahdc1 SUPPORTS TRANSFER The MGI:2444218 GO graph (historical snapshot dated 2023-03-10, inspected 2026-09-27) lists GO:0001707 by IMP from J:326009/PMID:35585237. The paper includes actual mouse mutagenesis as well as separate human differentiation experiments. Shared publication identity does not establish a circular transfer. ensembl:ENSMUSP00000101535 Β· mouse Ahdc1 protein SUPPORTS TRANSFER Ensembl protein identifier for the same mouse ortholog represented by Q6PAL7, rather than an independent experimental donor. Human and mouse developmental evidence in the cited primary study supports conserved involvement. Supporting Evidence: PMID:35585237 Single cell RNA sequencing (scRNA-seq) confirmed that mesodermal (PDGFRA+) cells as well as individual gene markers for that cluster were severely diminished in the GKO PMID:35585237 Consistent with in vitro findings (Fig. 4i), more severe mutants displayed skin stratification defects including loss of basal and suprabasal markers KRT14 and KRT10 |
| GO:0003700 DNA-binding transcription factor activity | IDA PMID:35585237 Gibbin mesodermal regulation patterns epithelial development... | MODIFY | Summary: Chromatin-associated transcription coregulation is supported; intrinsic motif recognition remains unresolved. Reason: The full PMID:35585237 study shows tagged AHDC1 occupancy at regulatory chromatin, BASU proximity to transcription/chromatin complexes, and a requirement for GATA3-induced transcription. Together these support a coregulatory role, including action through a complex, as defined by GO:0003712. GO:0003700 additionally requires selective binding to a specific DNA sequence; the examined ChIP and perturbation assays do not isolate that property of AHDC1 itself. Broad occupancy does not disprove sequence preference. The hESC ChIP used an inducible tagged transgene and a 5% 1,6-hexanediol pretreatment for 60 seconds; the effects of that treatment on particular AHDC1 contacts were not measured. The independent ENCODE HepG2 experiment uses a CRISPR-inserted endogenous-locus tag, not an untagged antibody assay. Both datasets support chromatin association without resolving intrinsic DNA recognition. The study includes motif analysis of GATA3 peaks, which does not establish an AHDC1 motif. Proposed replacements: transcription coregulator activity Supporting Evidence: PMID:35585237 Mass spectrometry revealed that the Gibbin interactome was heavily enriched for chromatin modifying complexes, enhancer binding proteins, and zinc finger TFs including the entire GATA family PMID:35585237 indicating that Gibbin is an important effector of GATA3 activity PMID:35585237 After 7 days of RA/BMP4, Gibbin primarily binds active promoters and enhancers |
| GO:0005515 protein binding | IPI PMID:16713569 A protein-protein interaction network for human inherited at... | REMOVE | Summary: The ATXN1 interaction does not provide an informative molecular-function term. Reason: The seeded PMID:16713569 interaction record identifies ATXN1 as the partner. The cached abstract describes a stringent yeast two-hybrid network and a tested subset validated in mammalian cells; the AHDC1-specific full experiment is not available here. Remove the generic protein-binding annotation as functionally uninformative, without declaring the pair false or assigning an unsupported specific replacement. The earlier IntAct construct analysis remains historical provenance, not a new binding-mechanism assay. Supporting Evidence: PMID:16713569 We identified 770 mostly novel protein-protein interactions using a stringent yeast two-hybrid screen |
| GO:0005515 protein binding | IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ... | REMOVE | Summary: Generic binding to HTT does not specify AHDC1 activity. Reason: PMID:32814053 is a neurodegenerative-disease interactome study. Its full primary text includes orthogonal DULIP validation of selected network pairs, so a paper-wide claim of no validation would be incorrect. An AHDC1-HTT-specific functional mechanism is not established by the source material inspected. Remove GO:0005515 as uninformative without denying the interaction or treating repeated database records as proof of either independent biological replication or false binding. Supporting Evidence: PMID:32814053 generated by systematic yeast two-hybrid interaction screening of βΌ500 ND-related proteins and integration of literature interactions |
| GO:0005515 protein binding | IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ... | REMOVE | Summary: The ATXN1 network interaction lacks a demonstrated AHDC1-specific functional assignment. Reason: The source records a candidate AHDC1-ATXN1 interaction in the neurodegeneration network. Network-level orthogonal validation in the full paper cannot be assumed to validate every pair, and recovery of a partner in two screens does not by itself establish a transcriptional mechanism. Remove the generic protein-binding term under the informative-function policy, while preserving the original partner and source record and leaving its physiological role open. Supporting Evidence: PMID:32814053 links many known ND-causing proteins, such as Ξ±-synuclein, TDP-43, and ATXN1, to a host of proteins previously unrelated to NDs |
| GO:0005634 nucleus | IDA PMID:33644933 Phenotypic and protein localization heterogeneity associated... | ACCEPT | Summary: Wild-type AHDC1 localizes to the nucleus. Reason: PMID:33644933 directly images fluorescently tagged wild-type human AHDC1 in HeLa cells, with selected constructs also studied in 293T cells. Wild-type protein forms foci in the nucleoplasm and around nucleoli and the nuclear perimeter. Mutant-specific diffuse or nucleolar patterns do not negate the wild-type nuclear localization, and coexpression did not measurably redirect the accompanying wild-type protein in the tested assay. Supporting Evidence: PMID:33644933 we observed that wild-type AHDC1 was expressed at distinct foci that surrounded the nucleoli and the inner perimeter of the nucleus. There were also distinct foci distributed throughout the nucleoplasm |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: The UniProt nuclear location is supported by direct human imaging. Reason: The SL-0191 mapping preserves the nucleus resolution of the curated UniProt location, which cites PMID:33644933. That paper directly images nuclear wild-type AHDC1; no finer replacement is needed for this broad source assertion. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB-SubCell:SL-0191 SUPPORTS TRANSFER UniProt nucleus vocabulary mapping; the cached AHDC1 location record explicitly cites the human imaging study PMID:33644933. Supporting Evidence: PMID:33644933 we observed that wild-type AHDC1 was expressed at distinct foci that surrounded the nucleoli and the inner perimeter of the nucleus. There were also distinct foci distributed throughout the nucleoplasm |
| GO:0005654 nucleoplasm | IDA GO_REF:0000052 | ACCEPT | Summary: Nucleoplasmic localization is consistent with HPA immunofluorescence. Reason: The original HPA-curated immunofluorescence assertion is retained at its reported resolution. Independent fluorescent-fusion imaging in PMID:33644933 also shows wild-type AHDC1 foci throughout the nucleoplasm. This corroboration supports the compartment without claiming that the experimental methods or antibody controls are identical. Supporting Evidence: PMID:33644933 we observed that wild-type AHDC1 was expressed at distinct foci that surrounded the nucleoli and the inner perimeter of the nucleus. There were also distinct foci distributed throughout the nucleoplasm |
| GO:0005694 chromosome | EXP PMID:35585237 Gibbin mesodermal regulation patterns epithelial development... | ACCEPT | Summary: AHDC1 occupies chromosomal regulatory regions in differentiating human cells. Reason: The full PMID:35585237 study reports ChIP-seq occupancy at active promoters and enhancers after RA/BMP4 induction, corroborated by the independent ENCODE HepG2 dataset. This supports the seeded broad chromosome compartment. ChIP establishes chromatin association in its assay context; it does not require interpreting AHDC1 as an intrinsic sequence-specific DNA-binding protein. Supporting Evidence: PMID:35585237 After 7 days of RA/BMP4, Gibbin primarily binds active promoters and enhancers |
| GO:0005694 chromosome | IEA GO_REF:0000044 | ACCEPT | Summary: The chromosome vocabulary mapping is supported at its source resolution. Reason: UniProt SL-0468 maps the curated chromosome location to GO:0005694. The underlying PMID:35585237 ChIP-seq experiments support association with chromosomal regulatory regions, so the broad location is retained without adding a redundant chromatin compartment assertion. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB-SubCell:SL-0468 SUPPORTS TRANSFER UniProt chromosome location mapping, with cached source evidence from PMID:35585237 regulatory-region ChIP-seq. Supporting Evidence: PMID:35585237 After 7 days of RA/BMP4, Gibbin primarily binds active promoters and enhancers |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000108 | MODIFY | Summary: AHDC1 regulates expression of protein-coding developmental genes. Reason: The logical inference starts from GO:0003700, whose intrinsic sequence-recognition component remains unresolved. Nevertheless, the process itself has independent experimental support: RNA-seq and GATA3 epistasis in PMID:35585237 show regulation of protein-coding lineage genes. The proposed RNA-polymerase-II transcription regulation term captures this demonstrated process without requiring AHDC1 to be the sequence-recognition module. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: GO:0003700 SOURCE WEAK OR INFERRED The inter-ontology source is the AHDC1 DNA-binding-transcription-factor assertion. Its intrinsic sequence specificity is unresolved; independent target-gene expression and epistasis experiments support the proposed process refinement. Proposed replacements: regulation of transcription by RNA polymerase II Supporting Evidence: PMID:35585237 By RNA-seq, expression of ~1,100 transcripts were significantly altered in the Gibbin KO (GKO) compared to wildtype (WT) PMID:35585237 indicating that Gibbin is an important effector of GATA3 activity |
| GO:0043589 skin morphogenesis | IDA PMID:35585237 Gibbin mesodermal regulation patterns epithelial development... | KEEP AS NON CORE | Summary: AHDC1 contributes to skin morphogenesis through mesodermal regulation. Reason: PMID:35585237 shows defective epidermal stratification after AHDC1 loss and rescue of mutant ectoderm by wild-type mesoderm. The study also documents abnormal skin differentiation in mosaic mutant mice. These results support developmental participation through AHDC1-dependent mesodermal transcription and dermal-to-epidermal signaling. They do not establish a cell-autonomous keratinocyte mechanism; retain skin morphogenesis as a contextual developmental process. Supporting Evidence: PMID:35585237 We then recombined the WT mesoderm with GKO ectoderm and found that this rescued the keratinocyte gene expression defects at day 50 PMID:35585237 Consistent with in vitro findings (Fig. 4i), more severe mutants displayed skin stratification defects including loss of basal and suprabasal markers KRT14 and KRT10 |
| GO:0043589 skin morphogenesis | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Mouse skin evidence supports conserved developmental involvement. Reason: The mouse Ahdc1 source has a recovered IMP chain to PMID:35585237 in the MGI snapshot. E18 mosaic mutant skin loses basal and suprabasal markers and shows abnormal attachment and stratification. The same publication includes independent human differentiation and recombination experiments, supporting the target process. This is a defensible ortholog transfer with developmental scope; use of one publication for distinct experiments is not evidence of circularity. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: UniProtKB:Q6PAL7 Β· mouse Ahdc1 SUPPORTS TRANSFER The MGI:2444218 GO graph (historical snapshot dated 2023-03-10, inspected 2026-09-27) lists GO:0043589 by IMP from J:326009/PMID:35585237. The paper includes actual mouse mutagenesis as well as separate human differentiation experiments. Shared publication identity does not establish a circular transfer. ensembl:ENSMUSP00000101535 Β· mouse Ahdc1 protein SUPPORTS TRANSFER Ensembl protein identifier for the same mouse ortholog represented by Q6PAL7, rather than an independent experimental donor. Human and mouse developmental evidence in the cited primary study supports conserved involvement. Supporting Evidence: PMID:35585237 Consistent with in vitro findings (Fig. 4i), more severe mutants displayed skin stratification defects including loss of basal and suprabasal markers KRT14 and KRT10 PMID:35585237 We then recombined the WT mesoderm with GKO ectoderm and found that this rescued the keratinocyte gene expression defects at day 50 |
| GO:0140585 promoter-enhancer loop anchoring activity | IDA PMID:35585237 Gibbin mesodermal regulation patterns epithelial development... | MODIFY | Summary: Chromatin association is demonstrated, while physical loop bridging is unresolved. Reason: GO:0140585 requires physically bridging cis-regulatory regions at loop anchors. The full source measures AHDC1 occupancy by ChIP-seq and altered cohesin-associated contacts after AHDC1 knockout by HiChIP. Loss of contacts establishes a regulatory requirement, but does not distinguish direct bridging by AHDC1 from effects mediated through methylation, CTCF or associated proteins. The positive AHDC1 ChIP-seq experiments support the broader chromatin-binding term GO:0003682; this replacement rests on those binding/association assays, not solely on the knockout contact phenotype. The inducible tagged hESC and endogenous-locus-tagged HepG2 experiments do not resolve direct DNA contact versus association through a chromatin complex. Proposed replacements: chromatin binding Supporting Evidence: PMID:35585237 After 7 days of RA/BMP4, Gibbin primarily binds active promoters and enhancers PMID:35585237 Lost chromatin contacts tended to be anchored at Gibbin-dependent gene promoters |
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Download this section (compressed HTML)Q: Does AHDC1 itself recognize a DNA sequence or chromatin feature, or is its regulatory-region occupancy mediated predominantly by associated proteins?
Q: Which physical interaction connects AHDC1 to DNA methyltransferase regulation, and can the proposed UHRF1-dependent mechanism be separated from downstream transcriptional effects?
Q: Does AHDC1 directly bridge regulatory regions, or does it stabilize their contacts through CTCF, methylation control or other chromatin factors?
Q: How do truncation-specific effects and changes in effective AHDC1 dosage contribute to Xia-Gibbs syndrome across tissues?
Experiment: Compare purified AHDC1 or validated folded fragments across DNA sequences and nucleosome substrates, with competition and binding-defective controls, to distinguish intrinsic recognition from cellular complex recruitment.
Experiment: Use acute AHDC1 depletion and separation-of-function rescue alongside nascent transcription, locus-specific methylation, CTCF occupancy and contact measurements to establish causal order before secondary differentiation changes.
What is not known β curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The examined cell-based studies do not resolve intrinsic AHDC1 DNA-sequence preferences or whether AHDC1 itself physically bridges regulatory regions.
OPEN BIOLOGY MF_DARK
What is known: Regulatory-chromatin occupancy, transcription-factor-associated complexes and functional effects on gene expression are supported by the 2022 human stem-cell and independent Ewing sarcoma studies. ChIP and co-immunoprecipitation do not isolate intrinsic recognition or bridge geometry.
What would resolve it: Reconstitute defined AHDC1 DNA/chromatin and partner-binding reactions, using sequence competition and separation-of-function mutants; measure physical bridging independently of downstream gene-expression changes.
Provenance (the field's own admissions):
Gap: Whether AHDC1 directly regulates the DNA-methylation machinery or changes methylation and chromatin contacts through downstream transcriptional effects remains unresolved.
OPEN BIOLOGY MF_DARK
What is known: In RA/BMP4-differentiating hESCs, knockout alters methylation, DNMT activity, CTCF occupancy and cohesin-associated contacts. BASU proximity identifies candidate chromatin partners, but does not establish the proposed UHRF1/DNMT effector mechanism or the causal order.
What would resolve it: Combine acute AHDC1 depletion, mechanistically defined rescue constructs and time-resolved transcription, methylation, CTCF and contact measurements; test candidate complexes directly.
Provenance (the field's own admissions):
Gap: The molecular pathway connecting mouse Ahdc1 deficiency to systemic metabolic phenotypes is unresolved at the abstract-level evidence examined here.
OPEN BIOLOGY BP_DARK
What is known: The primary abstract reports mouse obesity and reduced energy expenditure. Full experiments were not recovered in this audit, so no comprehensive absence of a mechanistic link and no human metabolic transfer are asserted.
What would resolve it: Read the complete mouse study and test tissue-specific AHDC1 regulatory targets before assigning a conserved human metabolic mechanism.
Provenance (the field's own admissions):
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