Neural ectoderm anteroposterior specification module

The developmental program that, during gastrulation, subdivides newly induced neural ectoderm along the anteroposterior axis into two parallel, lineage-committed brain progenitors: an OTX2-positive anterior neural ectoderm that generates the forebrain and midbrain, and a GBX2/HOX-positive posterior neural ectoderm that generates the hindbrain. The module begins where germ-layer specification ends - with SOX2-positive neural ectoderm established under combined BMP, TGF-beta and WNT inhibition - and is driven by a graded posteriorising input of FGF together with retinoic acid. That input is read out by a pair of mutually repressive homeodomain selectors, OTX2 and GBX2, whose shared border is the site at which the midbrain-hindbrain (isthmic) organizer forms; displacing the border displaces the organizer. The two territories are already committed rather than merely differently positioned: challenged with the opposite region's inducing signals they do not interconvert, and they carry diverging accessible-chromatin landscapes that foreshadow their regional identities. Downstream, the anterior territory resolves into FOXG1/SIX3 forebrain and EN1 midbrain progenitors, and the posterior territory into MAFB/HNF1B/HOXA3 rhombomere 5/6 hindbrain progenitors. Grounded in GO:0021999 (neural plate anterior/posterior regionalization). Upstream neural-versus-epidermal ectoderm allocation is supplied by modules/germ_layer_specification.yaml and modules/body_axis_specification.yaml; the signalling machinery is detailed in the fgfr_signaling, retinoic_acid_receptor_signaling, wnt_signaling, bmp_signaling and tgfb_smad_signaling modules; the cerebellar program that continues from the posterior territory's rhombomere 1 is in modules/cerebellum_development.yaml.

MODULE:neural_ectoderm_anteroposterior_specificationDRAFTABSTRACTDevelopmental Processmodules/neural_ectoderm_anteroposterior_specification.yaml

neural plate anterior/posterior regionalizationGO:0021999

GO:0021999

neural plate anterior/posterior regionalization

The module is grounded in the GO term for anteroposterior regionalization of the neural plate.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

Lineage tracing in mouse embryos and directed differentiation of human pluripotent stem cells establish that anterior and posterior neural ectoderm arise in parallel during gastrulation and are already committed to forebrain/midbrain versus hindbrain fates.

Two parallel brain progenitors emerge simultaneously during gastrulation: anterior neural ectoderm (forebrain/midbrain progenitor) and posterior neural ectoderm (hindbrain progenitor).

PMID:10490024

A role for Gbx2 in repression of Otx2 and positioning the mid/hindbrain organizer.

The shared OTX2/GBX2 border is instructive for organizer position, not a readout of it.

We propose that formation of a normal MHB organizer depends on a sharp Otx2 caudal border and that Gbx2 is required to position and sharpen this border.

PMID:7588062

Forebrain and midbrain regions are deleted in Otx2-/- mutants due to a defective anterior neuroectoderm specification during gastrulation.

Loss of the anterior selector deletes the forebrain and midbrain through failed specification at gastrulation rather than later degeneration.

These data suggest that Otx2 expression in endomesoderm and ectoderm is required for anterior neuroectoderm specification.

file:human/OTX2/OTX2-ai-review.yaml

OTX2 gene review

The anterior selector exemplar is reviewed in-repo, including the proposed GO:0030917 annotation that this module's selector-boundary part asserts.

file:human/GBX2/GBX2-ai-review.yaml

GBX2 gene review

The posterior selector exemplar is reviewed in-repo.

file:modules/neural_ectoderm_anteroposterior_specification-deep-research-falcon.md

Module deep research (falcon)

Independent module-level review, run after the module was drafted. It arrived at the same boundary decisions - treating neural induction, neural plate border specification, neuromesodermal/spinal-cord specification, isthmic-organizer signalling and the later regional programs as separate - and supplied three refinements that were folded in: the asymmetry of the two selector repression arms, the fact that the domains arise apart and are sharpened on contact rather than toggled, and the limits of the deuterostome conservation claim. Its cautions are recorded as knowledge_gaps.

Scope and boundary decisions. (1) The module starts at neural ectoderm, not at the epiblast: allocation of ectoderm to neural versus border versus surface fate under the BMP gradient already lives in germ_layer_specification, and duplicating it here would restate the same BMP switch twice. What is genuinely absent from the repo, and what this module supplies, is everything between "neural ectoderm exists" and "the brain has regions". (2) WNT is deliberately excluded from the posteriorising input even though it is a posteriorising signal. WNT activation at this stage specifies TBXT/CDX2 neuromesodermal progenitors and spinal cord, a parallel route that produces a different kind of posterior character; posterior neural ectoderm is induced by FGF and retinoic acid under WNT inhibition, and in the embryo lies outside the domain of active WNT signalling. Modelling WNT as an input here would merge two distinct posterior programs. It re-enters legitimately one step later, as an inducer of midbrain identity within the anterior territory and of hindbrain progenitors within the posterior one. (3) The exemplars are curated human UniProt accessions used to orient conserved roles; the program itself is not human-specific. Mutually exclusive otx-positive and gbx-positive ectoderm has been observed in mouse, macaque, chicken and zebrafish, and in the hemichordate Saccoglossus kowalevskii, so the scope is set at Deuterostomia rather than Vertebrata. (4) Gene-review coverage is uneven and the derived QC panel will say so: OTX2, GBX2, SOX2, FGF8 and EN1 have reviews in this repo; ALDH1A2, HOXA1, FOXG1, SIX3, MAFB, HNF1B and HOXA3 do not yet. The UniProt groundings are exact regardless, so the leaves are grounded even where the gene review is missing.

8Nodes

3Parts

2Variant Sets

4Variants

12Annotons

5Connections

Derived QC

Recommended-field compliance

84.8% recommended fields populated

knowledge_gaps[0] · provenance (0/1)
knowledge_gaps[1] · provenance (0/1)
knowledge_gaps[2] · provenance (0/1)
knowledge_gaps[3] · provenance (0/1)
knowledge_gaps[4] · provenance (0/1)

Module deep research

✓ present

neural_ectoderm_anteroposterior_specification-deep-research-falcon.md (falcon)

Leaf nodes lacking representative members

✓ representative grounding skipped for abstract module.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Reaction chaining (advisory)

✓ every PRECEDES step chains, or its break is acknowledged via chaining_status.

ap_selector_boundary → committed_regional_output [NOT_CHECKED]

Function consistency and core coverage

6 gene-function check(s) reflected in core functions · 0 conflict(s) · 6 evidence or coverage gap(s) (12 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

Annoton	Participant	Function	Assessment
ne_sox2	SOX2 UniProtKB:P48431 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
fgf_posteriorising_ligand	FGF8 UniProtKB:P55075 Gene	growth factor activity GO:0008083	Annotation Supported A retained annotation or curated replacement supports this function, but core_functions does not yet reflect it.
retinoic_acid_source	ALDH1A2 UniProtKB:O94788 Gene	retinal dehydrogenase (NAD+) activity GO:0001758	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
ane_otx2	OTX2 UniProtKB:P32243 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
pne_gbx2	GBX2 UniProtKB:P52951 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
pne_hox_anterior	HOXA1 UniProtKB:P49639 Gene	DNA-binding transcription factor activity GO:0000981	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
fb_foxg1	FOXG1 UniProtKB:P55316 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
fb_six3	SIX3 UniProtKB:O95343 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
mb_en1	EN1 UniProtKB:Q05925 Gene	DNA-binding transcription factor activity GO:0000981	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
r56_mafb	MAFB UniProtKB:Q9Y5Q3 Gene	DNA-binding transcription factor activity GO:0000981	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
r56_hnf1b	HNF1B UniProtKB:P35680 Gene	DNA-binding transcription factor activity GO:0000981	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.
r56_hoxa3	HOXA3 UniProtKB:O43365 Gene	DNA-binding transcription factor activity GO:0000981	Review Missing No ai-review exists for this protein; its function and core-function coverage cannot yet be checked.

Feedback loops (advisory, prose-driven: a regulator counts as "feedback" when its own description says so)

✓ every negative regulator described as feedback has an upstream edge closing the loop.

ane_otx2 ⊣ pne_gbx2 [input]
ane_otx2 is a negative regulator with no upstream edge (not described as feedback)
pne_gbx2 ⊣ ane_otx2 [input]
pne_gbx2 is a negative regulator with no upstream edge (not described as feedback)

Gene-review completeness (7/12 grounded genes reviewed)

4 complete review(s) · 2 with deep research · 5 missing review · 5 reviewed but lacking deep research

Gene	Review	Complete	Deep research
EN1 Q05925	✓	29/30	✗
FGF8 P55075	✓	193/195	✗
FOXG1 P55316	✓	✓	✗
GBX2 P52951	✓	✓	✗
HOXA3 O43365	✗	—	—
ALDH1A2 O94788	✗	—	—
OTX2 P32243	✓	36/37	✓
HNF1B P35680	✗	—	—
HOXA1 P49639	✗	—	—
MAFB Q9Y5Q3	✗	—	—
SIX3 O95343	✓	✓	✗
SOX2 P48431	✓	✓	✓

Tree

Anteroposterior specification of neural ectodermDevelopmental Processneural_ectoderm_anteroposterior_specification

Annotons
- SOX2 neural ectoderm identity factor Gene Product: SOX2
Parts
1. 1. extracellular input that biases identity posteriorly
2. Graded FGF and retinoic acid posteriorising inputRegulatory Stepposteriorising_signal_input
  
  Annotons
  - Posteriorising FGF ligand Gene Product: FGF8
  - Retinoic acid synthesising enzyme Gene Product: ALDH1A2
3. 2. the mutually repressive selector pair that partitions the territory
4. Mutually repressive OTX2/GBX2 selector boundaryDevelopmental Processap_selector_boundary
  
  Variants
  1. Parallel anterior and posterior neural ectoderm progenitors by anteroposterior neural ectoderm identity (Exactly One)
    
    Anterior neural ectoderm (forebrain/midbrain progenitor)Developmental Processanterior_neural_ectoderm
    
    Annotons
    
    OTX2 anterior identity selector Gene Product: OTX2
    
    Posterior neural ectoderm (hindbrain progenitor)Developmental Processposterior_neural_ectoderm
    
    Annotons
    
    GBX2 posterior identity selector Gene Product: GBX2
    
    Anterior HOX posterior-character factor Gene Product: HOXA1
5. 3. regional progenitors each territory is committed to produce
6. Committed regional progenitor outputDevelopmental Processcommitted_regional_output
  
  Variants
  1. Regional progenitors produced by each neural ectoderm territory by brain region produced (Exactly One)
    
    Forebrain and midbrain progenitors (from anterior neural ectoderm)Developmental Processforebrain_midbrain_progenitors
    
    Annotons
    
    FOXG1 telencephalic progenitor factor Gene Product: FOXG1
    
    SIX3 rostral forebrain factor Gene Product: SIX3
    
    EN1 midbrain identity factor Gene Product: EN1
    
    Rhombomere 5/6 hindbrain progenitors (from posterior neural ectoderm)Developmental Processrhombomere_5_6_progenitors
    
    Annotons
    
    MAFB rhombomere 5/6 factor Gene Product: MAFB
    
    HNF1B rhombomere 5/6 factor Gene Product: HNF1B
    
    HOXA3 caudal hindbrain positional factor Gene Product: HOXA3

Details

Context

deuterostomesNCBITaxon:33511

nucleusGO:0005634

Anteroposterior specification of neural ectodermDevelopmental Processneural_ectoderm_anteroposterior_specification

Subdivision of gastrula-stage neural ectoderm into parallel anterior (forebrain/midbrain) and posterior (hindbrain) progenitor populations, by a graded FGF plus retinoic acid input read out through mutual repression between the OTX2 and GBX2 selectors.

neural plate anterior/posterior regionalizationGO:0021999

Context

deuterostomesNCBITaxon:33511

nucleusGO:0005634

Annotons

SOX2 neural ectoderm identity factor

ne_sox2

Participant: Gene Product: SOX2

Gene Product:

SOX2UniProtKB:P48431 SoxB1 factor marking neural ectoderm throughout this module; both the anterior and the posterior territory are SOX2-positive, and the anteroposterior selectors are superimposed on this shared identity rather than replacing it (see file:human/SOX2/SOX2-ai-review.yaml).

Function

DNA-binding transcription factor activityGO:0000981

Locations

nucleusGO:0005634

Shared neural ectoderm marker defining the population that this module subdivides; it is the label used to identify both progenitors and does not itself carry regional information. No process term is asserted here, deliberately. GO:0021999 describes the regionalization that the OTX2/GBX2 selectors perform, whereas SOX2 marks the population being subdivided rather than doing that work, so the module-level concept carries GO:0021999 and this participant does not.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

Both progenitors are defined within the SOX2-positive neural ectoderm compartment, distinguished by OTX2 versus GBX2.

Two parallel brain progenitors emerge simultaneously during gastrulation: anterior neural ectoderm (forebrain/midbrain progenitor) and posterior neural ectoderm (hindbrain progenitor).

Connections

posteriorising_signal_input -> ap_selector_boundary Provides Input For

Combined FGF and retinoic acid activity is the extracellular input that selects the posterior branch of the selector variant set; in its absence, and under BMP, TGF-beta and WNT inhibition, neural ectoderm adopts the anterior branch by default.

ap_selector_boundary -> committed_regional_output Precedes

Selector identity is established first and constrains what regional progenitors can subsequently be induced; the chromatin landscapes of the two territories diverge before overt regional identity appears, which is the proposed mechanism of the commitment.

ne_sox2 -> ap_selector_boundary Part Of

The selector boundary is drawn within the SOX2-positive neural ectoderm population, not between it and another germ layer derivative.

Part 1: extracellular input that biases identity posteriorly

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

A WNT reporter is largely absent from the gbx-positive territory at E7.5 and instead marks the posterior-most TBXT/CDX2 region, which is why WNT is not modelled as an input to this part.

WNT is not modelled as an input to this part. In the E7.5 embryo the gbx-positive territory is largely devoid of WNT reporter activity; WNT activity instead marks the posterior-most region where TBXT/CDX2 neuromesodermal and spinal cord progenitors lie, and posterior neural ectoderm induction in vitro requires WNT inhibition. FGF plus retinoic acid and WNT therefore produce two different kinds of posterior character, and conflating them would merge the hindbrain and spinal cord routes. Provenance caveat: the in-vivo reporter observation is from the figures of PMID:42760324 (see this part's evidence entry), whose cached record here is abstract-only, so it is cited without a verbatim quote. It is the weakest-sourced statement in this module and the reason WNT is excluded should be read at that strength.

Graded FGF and retinoic acid posteriorising inputRegulatory Stepposteriorising_signal_input

The extracellular input that biases neural ectoderm towards posterior identity. FGF and retinoic acid are combinatorially required: either alone is insufficient to induce GBX2 and repress OTX2. In the embryo both sources lie adjacent to the prospective posterior territory, and the territory itself is outside the domain of active WNT signalling.

positive regulation of posterior neural plate formation by FGF receptor signalingGO:0060787 retinoic acid receptor signaling pathwayGO:0048384

Annotons

Posteriorising FGF ligand

fgf_posteriorising_ligand

Participant: Gene Product: FGF8

Gene Product:

FGF8UniProtKB:P55075 Exemplar of the FGF ligand supplied from tissue adjacent to the prospective posterior neural ectoderm; FGF8 is the family member whose expression domain abuts the gbx-positive territory and which later marks the isthmic organizer itself (see file:human/FGF8/FGF8-ai-review.yaml).

Function

growth factor activityGO:0008083

Processes

positive regulation of posterior neural plate formation by FGF receptor signalingGO:0060787

Locations

extracellular regionGO:0005576

Secreted posteriorising signal; required together with retinoic acid to induce the posterior selector and repress the anterior one.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

FGF and retinoic acid activation with BMP, TGF-beta and WNT blockade specifies posterior neural ectoderm from human definitive ectoderm in 24 h, and neither signal suffices alone.

Retinoic acid synthesising enzyme

retinoic_acid_source

Participant: Gene Product: ALDH1A2

Gene Product:

ALDH1A2UniProtKB:O94788 RALDH2, the retinaldehyde dehydrogenase whose expression domain lies immediately adjacent to the posterior neural ectoderm and which supplies the retinoic acid arm of the posteriorising input. Placed here as the source of the signal, not as a member of the neural ectoderm itself.

Function

retinal dehydrogenase (NAD+) activityGO:0001758

Processes

retinoic acid biosynthetic processGO:0002138

Locations

cytosolGO:0005829

Generates the retinoic acid that, with FGF, is combinatorially required to induce posterior neural ectoderm identity.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

In situ staining places the retinoic acid synthesis enzyme Raldh2/Aldh1a2 adjacent to posterior neural ectoderm in the E7.5 mouse embryo.

Part 2: the mutually repressive selector pair that partitions the territory

Mutually repressive OTX2/GBX2 selector boundaryDevelopmental Processap_selector_boundary

The core of the module. Two homeodomain selectors occupy complementary territories within neural ectoderm and repress one another, producing a sharp interface. The interface is where the midbrain-hindbrain organizer assembles, and it is instructive for organizer position: shifting the border relocates the organizer and correspondingly expands or reduces the brain regions on either side. It positions the organizer rather than being a sufficient linear switch for it - FGF8 expression is still seen in neuroectoderm lacking both selectors, which suggests the pair refines rather than induces FGF8 expression. The domains also arise independently before they meet and are sharpened on contact rather than resolved by a single instantaneous toggle: in chick, Otx2 and Gbx2 occupy the rostral and caudal portions of the embryo at HH4, are not yet contiguous at HH8 with a small gap of expression between them, overlap slightly at HH9, and are contiguous and mutually exclusive by HH10.

midbrain-hindbrain boundary developmentGO:0030917

PMID:35401126

An update on the molecular mechanism of the vertebrate isthmic organizer development in the context of the neuromeric model.

The two domains are established independently and only then brought into register by mutual antagonism, which is why this part is not modelled as a single instantaneous toggle.

Otx2- and Gbx2- expressing domains are firstly established independently of each other, with antagonistic interactions between them as development proceeds to create the Otx2/Gbx2 MH interface

PMID:35401126

An update on the molecular mechanism of the vertebrate isthmic organizer development in the context of the neuromeric model.

In chick the two selector domains are not contiguous at HH8 and overlap only slightly at HH9, so the interface is sharpened progressively.

While the expressing domains of both genes are not contiguous at stage HH8, with a small gap of expression between them, a slight overlap is observed at stage HH9

PMID:35401126

An update on the molecular mechanism of the vertebrate isthmic organizer development in the context of the neuromeric model.

By HH10 the interface is complementary and exclusive, which is the state this part models.

At stage HH10, the Otx2-expressing domain and the Gbx2-expressing domain are contiguous and exclusive

PMID:23307071

Novel mechanisms that pattern and shape the midbrain-hindbrain boundary.

FGF8 expression is still observed without either selector, which the source reads as the pair refining rather than inducing FGF8 expression - the reason this part is not modelled as a sufficient linear switch.

FGF8 is still observed within the neuroectoderm in the absence of both these factors

file:modules/neural_ectoderm_anteroposterior_specification-deep-research-falcon.md

Module deep research (falcon)

Independent review flags the asymmetry of the two repression arms and the chick timing of domain establishment, and cautions against reading the selector pair as a universally sufficient switch for organizer induction.

OTX proteins reciprocally help exclude posterior identities and regulate midbrain competence, but “mutual repression” should be interpreted carefully.

Connections

ane_otx2 -> pne_gbx2 Negatively Regulates

The anterior selector helps exclude posterior identity from its territory. This arm is the weaker of the two and is asserted as such: it rests on complementary, non-overlapping expression domains and on reciprocal mutant phenotypes (OTX loss produces anterior and midbrain competence defects and repositions Fgf8), not on demonstrated occupancy of the posterior selector's regulatory elements. Direct enhancer occupancy and the symmetry of the two arms remain incompletely defined across vertebrates.

pne_gbx2 -> ane_otx2 Negatively Regulates

The posterior selector represses the anterior one and thereby positions and sharpens the shared border. This is the directional arm with gain- and loss-of-function support: without it the anterior domain expands posteriorly, and forcing it inside the anterior domain relocates the border and the organizer.

PMID:10490024

A role for Gbx2 in repression of Otx2 and positioning the mid/hindbrain organizer.

A sharp anterior-selector border, maintained by the posterior selector, is required for a normal midbrain-hindbrain organizer.

We propose that formation of a normal MHB organizer depends on a sharp Otx2 caudal border and that Gbx2 is required to position and sharpen this border.

Variant set: Parallel anterior and posterior neural ectoderm progenitors by anteroposterior neural ectoderm identity (Exactly One)

Anterior neural ectoderm (forebrain/midbrain progenitor)Developmental Processanterior_neural_ectoderm

SOX2-positive, OTX2-positive, GBX2-negative territory induced by BMP, TGF-beta and WNT inhibition in the absence of FGF and retinoic acid. Committed to forebrain and midbrain fate; it does not acquire hindbrain identity when challenged with hindbrain-inducing signals.

anterior neural plate formationGO:0090017

Annotons

OTX2 anterior identity selector

ane_otx2

Participant: Gene Product: OTX2

Gene Product:

OTX2UniProtKB:P32243 Bicoid-class homeodomain selector defining anterior neural identity; its caudal border is the site of isthmic organizer formation (see file:human/OTX2/OTX2-ai-review.yaml).

Function

DNA-binding transcription factor activityGO:0000981

Processes

midbrain-hindbrain boundary developmentGO:0030917 forebrain developmentGO:0030900 midbrain developmentGO:0030901

Locations

nucleusGO:0005634

Anterior selector. Confers forebrain/midbrain competence and, by the caudal limit of its domain, sets where along the axis the organizer forms.

PMID:7588062

Forebrain and midbrain regions are deleted in Otx2-/- mutants due to a defective anterior neuroectoderm specification during gastrulation.

Loss of the selector removes the forebrain and midbrain through failed specification during gastrulation.

By 9.5 dpc, homozygous mutant embryos are characterized by the absence of forebrain and midbrain regions.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

Human OTX2-positive anterior neural ectoderm is lineage committed and does not convert to hindbrain under hindbrain-inducing signals.

Differentiation of human pluripotent stem cells into anterior or posterior neural ectoderm-like cells revealed these were lineage committed to forebrain/midbrain versus hindbrain fates, respectively.

Posterior neural ectoderm (hindbrain progenitor)Developmental Processposterior_neural_ectoderm

SOX2-positive, GBX2-positive, OTX2-low territory induced by FGF and retinoic acid under BMP, TGF-beta and WNT blockade, additionally expressing anterior HOX genes. Committed to hindbrain fate and negative for the neuromesodermal and spinal cord markers TBXT and CDX2, which distinguishes it from the WNT-dependent posterior route.

posterior neural plate formationGO:0090018

Annotons

GBX2 posterior identity selector

pne_gbx2

Participant: Gene Product: GBX2

Gene Product:

GBX2UniProtKB:P52951 Homeodomain selector conferring anterior-hindbrain identity by repressing the anterior selector and sharpening its border (see file:human/GBX2/GBX2-ai-review.yaml).

Function

DNA-binding transcription factor activityGO:0000981

Processes

midbrain-hindbrain boundary developmentGO:0030917 hindbrain developmentGO:0030902

Locations

nucleusGO:0005634

Posterior selector. Represses the anterior selector, positions and sharpens the shared border, and confers hindbrain competence.

PMID:10490024

A role for Gbx2 in repression of Otx2 and positioning the mid/hindbrain organizer.

Loss of the posterior selector allows the anterior domain to expand posteriorly, and ectopic expression shifts the border rostrally with a functional organizer forming at the new position.

we transiently expressed Gbx2 in the caudal Otx2 domain and found that the Otx2 caudal border was indeed shifted rostrally and a normal appearing organizer formed at this new Otx2 border.

PMID:16651541

A threshold requirement for Gbx2 levels in hindbrain development.

The hindbrain-competence half of this role. Anterior rhombomeres require the selector - without it r1-r3 fail to develop and no cerebellum forms - and the requirement is dose-graded rather than all-or-none.

In Gbx2 null homozygotes, rhombomeres (r) 1-3 fail to develop and the isthmic expression of Fgf8 is reduced and disorganized

PMID:16651541

A threshold requirement for Gbx2 levels in hindbrain development.

The dose-graded form of the same requirement, from this paper's own hypomorph.

reduced Gbx2 expression is sufficient to support the development of r3 but not r2

Anterior HOX posterior-character factor

pne_hox_anterior

Participant: Gene Product: HOXA1

Gene Product:

HOXA1UniProtKB:P49639 Exemplar of the paralogue-group-1 HOX factors (HOXA1, HOXB1) that are induced together with the posterior selector and supply hindbrain-level positional identity. Listed as an exemplar of the anterior HOX role, not as the sole member.

Function

DNA-binding transcription factor activityGO:0000981

Processes

hindbrain developmentGO:0030902

Locations

nucleusGO:0005634

Supplies anteroposterior positional identity within the posterior territory, distinguishing hindbrain level from the more caudal spinal cord program.

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

Posterior neural ectoderm expresses the posterior markers Hoxa1 and Hoxb1 in vivo and HOXA1 in the human in vitro system.

Part 3: regional progenitors each territory is committed to produce

PMID:42760324

Two parallel neural ectoderm progenitors contribute to the developing brain.

Each territory produces only its own regional progenitors: posterior neural ectoderm challenged with forebrain- or midbrain-inducing signals largely fails to acquire those identities, and anterior neural ectoderm challenged with hindbrain conditions fails to become hindbrain. Human rhombomere 5/6 progenitors expressing MAFB, HNF1B and HOXA3 were generated from posterior neural ectoderm.

Committed regional progenitor outputDevelopmental Processcommitted_regional_output

The regional progenitors each territory produces. This part exists to make the commitment claim modelable: the outputs are determined by which selector territory a cell came from rather than by the regional signals it later encounters, so the two branches do not interconvert even when given the other branch's inducing conditions. WNT re-enters here legitimately, as an instructive signal within each territory rather than as an input to the anteroposterior split.

Variant set: Regional progenitors produced by each neural ectoderm territory by brain region produced (Exactly One)

Forebrain and midbrain progenitors (from anterior neural ectoderm)Developmental Processforebrain_midbrain_progenitors

Anterior neural ectoderm bifurcates into FOXG1/SIX3 forebrain progenitors when the posteriorising signals WNT and BMP are blocked and FGF is active, or into EN1 midbrain progenitors when WNT and FGF are active - consistent with the posterior WNT gradient across the developing forebrain and midbrain in vivo.

forebrain regionalizationGO:0021871 midbrain developmentGO:0030901

Annotons

FOXG1 telencephalic progenitor factor

fb_foxg1

Participant: Gene Product: FOXG1

Gene Product:

FOXG1UniProtKB:P55316 Forkhead factor marking committed forebrain progenitors derived from anterior neural ectoderm.

Function

DNA-binding transcription factor activityGO:0000981

Processes

forebrain regionalizationGO:0021871

Locations

nucleusGO:0005634

Marks and drives the forebrain branch of the anterior territory.

SIX3 rostral forebrain factor

fb_six3

Participant: Gene Product: SIX3

Gene Product:

SIX3UniProtKB:O95343 Homeodomain factor co-induced with FOXG1 in forebrain progenitors under WNT and BMP inhibition.

Function

DNA-binding transcription factor activityGO:0000981

Processes

forebrain regionalizationGO:0021871

Locations

nucleusGO:0005634

Rostral forebrain identity factor within the anterior branch.

EN1 midbrain identity factor

mb_en1

Participant: Gene Product: EN1

Gene Product:

EN1UniProtKB:Q05925 Engrailed factor marking midbrain progenitors; induced from anterior neural ectoderm by combined WNT and FGF activation (see file:human/EN1/EN1-ai-review.yaml).

Function

DNA-binding transcription factor activityGO:0000981

Processes

midbrain developmentGO:0030901

Locations

nucleusGO:0005634

Marks the midbrain branch of the anterior territory, induced where WNT activity is high across the anterior neural plate.

Rhombomere 5/6 hindbrain progenitors (from posterior neural ectoderm)Developmental Processrhombomere_5_6_progenitors

Posterior neural ectoderm differentiates into hindbrain progenitors on combined FGF and WNT activation, adopting a rhombomere 5/6 identity defined by the coincident expression of MAFB, HNF1B and HOXA3 - consistent with the in vivo requirement for FGF in rhombomere 5 and 6 specification. These progenitors go on to form ISL1-positive cholinergic hindbrain motor neurons.

rhombomere 5 developmentGO:0021571 hindbrain developmentGO:0030902

Annotons

MAFB rhombomere 5/6 factor

r56_mafb

Participant: Gene Product: MAFB

Gene Product:

MAFBUniProtKB:Q9Y5Q3 bZIP factor (Kreisler/Krml1) whose expression defines rhombomeres 5 and 6 in the segmented hindbrain.

Function

DNA-binding transcription factor activityGO:0000981

Processes

rhombomere 5 developmentGO:0021571

Locations

nucleusGO:0005634

Segmental identity factor for rhombomeres 5 and 6.

HNF1B rhombomere 5/6 factor

r56_hnf1b

Participant: Gene Product: HNF1B

Gene Product:

HNF1BUniProtKB:P35680 Homeodomain factor (vHNF1) co-expressed with MAFB in the caudal hindbrain and part of the rhombomere 5/6 signature; despite the name, its role here is segmental patterning rather than endodermal.

Function

DNA-binding transcription factor activityGO:0000981

Processes

rhombomere 5 developmentGO:0021571

Locations

nucleusGO:0005634

Co-defines rhombomere 5/6 identity with MAFB; the pair is what distinguishes these progenitors from other hindbrain segments.

HOXA3 caudal hindbrain positional factor

r56_hoxa3

Participant: Gene Product: HOXA3

Gene Product:

HOXA3UniProtKB:O43365 Paralogue-group-3 HOX factor whose anterior expression limit falls within the caudal hindbrain, completing the rhombomere 5/6 code.

Function

DNA-binding transcription factor activityGO:0000981

Processes

rhombomere 5 developmentGO:0021571

Locations

nucleusGO:0005634

Supplies the HOX-level positional coordinate of the rhombomere 5/6 identity.