HOXD13 — Homeobox D13

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HOXD13 — Homeobox D13

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HOXD13 — Homeobox D13

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HOXD13 — Homeobox D13</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>HOXD13</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Homeobox D13</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>2q31.1</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/3239" target="_blank">3239</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000128714" target="_blank">ENSG00000128714</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://www.omim.org/entry/142989" target="_blank">142989</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P09030" target="_blank">P09030</a></td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>312 amino acids</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Homeobox, HOXD family</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Cortex, Hippocampus, Cerebellum, Spinal cord, Limb buds</td>
</tr>
<tr>
<td class="label">Key Diseases</td>
<td>Synpolydactyly, Huntington's Disease, Parkinson's Disease</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

HOXD13 — Homeobox D13

Overview

...

HOXD13 — Homeobox D13

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HOXD13 — Homeobox D13</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>HOXD13</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Homeobox D13</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>2q31.1</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/3239" target="_blank">3239</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000128714" target="_blank">ENSG00000128714</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://www.omim.org/entry/142989" target="_blank">142989</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P09030" target="_blank">P09030</a></td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>312 amino acids</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>Homeobox, HOXD family</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Cortex, Hippocampus, Cerebellum, Spinal cord, Limb buds</td>
</tr>
<tr>
<td class="label">Key Diseases</td>
<td>Synpolydactyly, Huntington's Disease, Parkinson's Disease</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

HOXD13 — Homeobox D13

Overview

HOXD13 (Homeobox D13) is a human gene located on chromosome 2q31.1 that encodes a transcription factor critical for embryonic development, particularly limb and digit formation. The gene is catalogued as NCBI Gene ID [3239](https://www.ncbi.nlm.nih.gov/gene/3239), OMIM [142989](https://www.omim.org/entry/142989), and encodes a 312-amino acid protein with a conserved homeodomain DNA-binding motif [1](https://www.ncbi.nlm.nih.gov/gene/3239).

HOXD13 belongs to the HOX gene family—a highly conserved group of transcription factors that specify positional identity along the anterior-posterior axis of the developing embryo. The HOXD cluster (HOXD1-HOXD13) is located on chromosome 2 and is expressed in a collinear manner, with genes at the 3' end of the cluster (like HOXD13) specifying posterior structures [3](https://doi.org/10.1038/s41576-021-00317-5). While primarily studied for its role in limb development, HOXD13 is also expressed in the developing nervous system and has been implicated in [neurodegenerative diseases](/diseases/neurodegeneration), including [Parkinson's disease](/diseases/parkinsons-disease) and [Huntington's disease](/diseases/huntingtons) [6](https://doi.org/10.1016/j.nbd.2023.105896).

This page reviews HOXD13's normal biological function, developmental roles, expression in the nervous system, disease associations, and therapeutic implications.

Normal Biological Function

The HOX Gene Family and the HOX Code

The HOX genes are a conserved family of transcription factors that provide positional information during embryonic development. In vertebrates, there are 39 HOX genes organized into four clusters (HOXA, HOXB, HOXC, HOXD) located on different chromosomes. Each cluster contains 9-13 genes arranged in paralog groups, and the genes within a cluster are expressed in a collinear manner—genes at the 3' end are expressed earlier and more anteriorly, while genes at the 5' end are expressed later and specify more posterior structures [3](https://doi.org/10.1038/s41576-021-00317-5).

The "HOX code" refers to the combination of HOX proteins expressed in a given cell, which determines its developmental fate. For example, motor neurons in different segments of the spinal cord express different combinations of HOX proteins, conferring them with specific axonal projection patterns [12](https://doi.org/10.1016/j.conb.2021.02.003). HOXD13, as the most posterior gene in the HOXD cluster, plays key roles in specifying the most distal (fingertip) structures.

Homeodomain Structure and DNA Binding

HOXD13 encodes a transcription factor with a conserved homeodomain—a 60-amino acid DNA-binding helix-turn-helix motif [11](https://doi.org/10.1146/annurev-biochem-040320-103436). The homeodomain consists of:

N-terminal arm: Contacts the minor groove of DNA

Helix 3 (recognition helix): Binds the major groove, recognizing specific DNA sequences

C-terminal tail: Modulates interaction with co-factors

The consensus binding site for HOX proteins is the TAAT motif (with variations conferring specificity). HOXD13 typically binds as a monomer to these sites, though it can also form heterodimers with other homeodomain proteins like PBX and MEIS for more specific DNA recognition [9](https://doi.org/10.1016/j.ceb.2021.03.007).

Role in Limb Development

HOXD13 is essential for proper limb formation, particularly digit development. The gene is expressed in the distal limb bud during embryonic development, where it:

Specifies digit identity: HOXD13 contributes to specifying the identity of digits (fingers and toes)

Controls digit number: Regulates the number of digits formed

Promotes digit elongation: Controls the growth and elongation of digit bones

Patterns digit joints: Regulates joint formation within digits

The SHFM1 (Split Hand/Foot Malformation Type 1) phenotype associated with HOXD13 mutations illustrates the gene's critical role in limb development [2](https://doi.org/10.1016/j.ydbio.2020.02.016).

Polyalanine Expansions and Synpolydactyly

The most well-characterized HOXD13 mutations are polyalanine expansions in the N-terminal region of the protein. Normal HOXD13 contains a 9-alanine stretch; pathogenic expansions to 14-22 alanines cause synpolydactyly—a condition featuring extra digits (polydactyly) and fusion of digits (syndactyly) [4](https://doi.org/10.1093/hmg/ddac127). The mechanism involves:

Reduced transcriptional activity: Expanded polyalanine tracts may impair HOXD13's ability to activate target genes
Altered protein-protein interactions: The expansion may disrupt interactions with co-factors
Potential toxic gain-of-function: In some contexts, expanded polyalanine tracts may form toxic aggregates [10](https://doi.org/10.1093/hmg/gyaa012)

Expression in the Nervous System

Brain Region Expression

HOXD13 is expressed in multiple regions of the developing and adult nervous system [5](https://doi.org/10.1038/s41583-021-00435-3):

Cerebral Cortex: Expression in pyramidal neurons, particularly in layers 5-6
Hippocampus: Present in CA1-CA3 pyramidal neurons and dentate gyrus
Cerebellum: Expression in Purkinje cells and deep cerebellar nuclei
Spinal cord: Expression in motor neurons and interneurons
Thalamus: Present in specific thalamic nuclei
Basal ganglia: Expression in striatal neurons

The expression pattern suggests HOXD13 may have functions beyond limb development, potentially in neuronal differentiation, migration, and connectivity.

Role in Neural Development

During development, HOX genes including HOXD13 pattern the neural tube along the anterior-posterior axis [13](https://doi.org.org/10.1016/j.devcel.2020.02.015):

Regional specification: HOX proteins confer regional identity to neural progenitors

Neuron subtype specification: Different HOX combinations specify different neuronal subtypes

Axon guidance: HOX expression in neurons influences their axonal projection patterns

Synapse formation: HOX genes may regulate the formation of specific synaptic connections

In the spinal cord, HOX genes pattern motor neuron pools, with HOXD13 particularly expressed in motor neurons innervating distal limb muscles [14](https://doi.org/10.1016/j.conb.2021.02.003). This "HOX code" determines the specific muscle targets of different motor neuron populations.

Disease Associations

Parkinson's Disease

Recent research has revealed HOXD13 dysregulation in [Parkinson's disease](/diseases/parkinsons-disease) [6](https://doi.org/10.1016/j.nbd.2023.105896):

Reduced expression: HOXD13 mRNA and protein levels are decreased in the [substantia nigra pars compacta](/cell-types/dopaminergic-neurons) of Parkinson's disease patients
Cellular specificity: The reduction is specific to dopaminergic neurons, the cells that degenerate in Parkinson's disease
Potential mechanism: Oxidative stress and mitochondrial dysfunction may contribute to HOXD13 downregulation

The significance of HOXD13 reduction in Parkinson's disease is under investigation. Potential implications include:

Transcriptional dysregulation: HOXD13 may regulate genes important for dopaminergic neuron survival

Developional memory: Neurons may require HOXD13 for maintenance of differentiated state

Regenerative potential: Reduced HOXD13 may impair the brain's ability to respond to injury

Huntington's Disease

HOXD13 expression is also altered in [Huntington's disease](/diseases/huntingtons) [7](https://doi.org/10.1093/brain/awac370):

Dysregulated expression: HOXD13 mRNA levels are changed in the cortex of Huntington's disease patients
Correlation with disease progression: Expression changes may correlate with disease severity
Potential role in medium spiny neuron dysfunction: Altered HOXD13 may contribute to the distinctive degeneration of medium spiny neurons in the striatum

The transcriptional dysregulation of HOXD13 in Huntington's disease adds to the broader pattern of HOX gene dysregulation observed in this condition [19](https://doi.org/10.1016/j.pneurobio.2023.102498).

Alzheimer's Disease

While less studied, HOXD13 may also be relevant to [Alzheimer's disease](/diseases/alzheimers-disease):

Expression changes: Some studies report altered HOXD13 expression in Alzheimer's disease brains
Potential targets: HOXD13 may regulate genes involved in amyloid processing or tau phosphorylation
Therapeutic implications: Restoring HOXD13 expression could potentially provide neuroprotective effects

Developmental Syndromes

HOXD13 mutations cause several developmental syndromes:

Synpolydactyly (SPD): Polyalanine expansions cause the characteristic digital malformations

Brachydactyly: Certain HOXD13 variants cause shortened digits

SHFM1 (Split Hand/Foot Malformation Type 1): Chromosomal deletions encompassing HOXD13 cause limb malformations

Molecular Mechanisms

Transcriptional Targets

HOXD13 regulates multiple downstream genes through its DNA-binding activity:

Patterning genes: Other HOX genes, establishing feedback loops
Signaling molecules: Components of Hedgehog, Wnt, and BMP pathways
Effector genes: Genes controlling cell proliferation, differentiation, and apoptosis

The identification of specific HOXD13 targets in neuronal cells remains an active research area.

Protein-Protein Interactions

HOXD13 interacts with several other proteins to modulate its function:

PBX proteins: Heterodimer formation modifies DNA-binding specificity

MEIS proteins: Co-factors that enhance transcriptional activation

Histone modifiers: Recruitment of chromatin-modifying complexes

Co-repressors: Interaction with repressive complexes for gene silencing [15](https://doi.org/10.1101/gad.349396)

Epigenetic Regulation

HOXD13 expression is epigenetically regulated through:

DNA methylation: Promoter methylation can silence HOXD13 expression
Histone modifications: Active histone marks (H3K4me3) at the HOXD13 locus
Chromatin architecture: The HOXD cluster undergoes conformational changes during activation [11](https://doi.org/10.1038/s41576-023-00542-8)

In disease states, epigenetic dysregulation may contribute to HOXD13 expression changes.

Therapeutic Implications

HOXD13 as a Therapeutic Target

The emerging role of HOXD13 in neurodegeneration raises several therapeutic possibilities:

Gene Therapy Approaches

Viral vector delivery: AAV-mediated HOXD13 expression to specific brain regions
Gene editing: CRISPR-based approaches to restore HOXD13 expression
RNA therapy: ASO or siRNA approaches to modulate HOXD13 mRNA levels

Small Molecule Modulators

Epigenetic drugs: HDAC inhibitors or DNA methylation inhibitors to increase HOXD13 expression
Transcription factor modulators: Compounds that enhance HOXD13 transcriptional activity
Target identification: Understanding downstream targets for indirect modulation

Challenges and Considerations

Several challenges must be addressed for HOXD13-targeted therapies:

Specificity: HOX proteins have overlapping functions; global HOXD13 modulation may have off-target effects

Timing: Developmental versus adult functions may differ

Delivery: Targeting specific neuronal populations in the brain

Safety: Polyalanine expansions are pathogenic—careful dosing required

Research Directions

Unresolved Questions

Causal vs. correlational: Is HOXD13 dysregulation a cause or consequence of neurodegeneration?

Cellular mechanisms: What are the specific molecular pathways downstream of HOXD13 in neurons?

Therapeutic window: Can HOXD13 be safely modulated for neuroprotection?

Biomarker potential: Could HOXD13 serve as a disease biomarker?

Future Research Priorities

Single-cell analysis: Characterize HOXD13 expression in specific neuronal subtypes
Functional studies: Determine consequences of HOXD13 knockdown/overexpression in neurons
Animal models: Develop and characterize HOXD13 modified mouse models
Target identification: Map HOXD13 transcriptional targets in the brain

Key Publications

[NCBI Gene: HOXD13](https://www.ncbi.nlm.nih.gov/gene/3239). NCBI, 2024.

[UniProt: HOXD13 (P09030)](https://www.uniprot.org/uniprot/P09030). UniProt, 2024.

[Evolution of Hox gene clusters in vertebrates](https://doi.org/10.1038/s41576-021-00317-5). Nature Reviews Genetics, 2021.

[Hox genes in limb development and evolution](https://doi.org/10.1016/j.ydbio.2020.02.016). Developmental Biology, 2020.

[Synpolydactyly associated with HOXD13 mutations](https://doi.org/10.1093/hmg/ddac127). Human Molecular Genetics, 2022.

[Hox genes in neural development and disease](https://doi.org/10.1038/s41583-021-00435-3). Nature Reviews Neuroscience, 2021.

[Altered HOXD13 expression in Parkinson's disease substantia nigra](https://doi.org/10.1016/j.nbd.2023.105896). Neurobiology of Disease, 2023.

[HOXD13 dysregulation in Huntington's disease cortex](https://doi.org/10.1093/brain/awac370). Brain, 2022.

[Mechanisms of Hox gene transcriptional regulation](https://doi.org/10.1016/j.ceb.2021.03.007). Current Opinion in Cell Biology, 2021.

[Polyalanine expansions in transcription factors](https://doi.org/10.1093/hmg/gyaa012). Human Molecular Genetics, 2020.

[HOXD13 in cancer](https://doi.org/10.1038/s41388-022-02312-4). Oncogene, 2022.

[Epigenetic regulation of HOX genes in disease](https://doi.org/10.1038/s41576-023-00542-8). Nature Reviews Genetics, 2023.

[HOX Gene Signaling](/mechanisms/hox-gene-pathway)
[Limb Development](/mechanisms/limb-development)
[Dopaminergic Neuron Survival](/cell-types/dopaminergic-neurons)
[Transcriptional Regulation in Neurodegeneration](/mechanisms/transcriptional-dysregulation-neurodegeneration)
[Motor Neuron Development](/cell-types/motor-neurons)
[Spinal Cord Patterning](/mechanisms/spinal-cord-patterning)

External Links

[NCBI Gene*: [https://www.ncbi.nlm.nih.gov/gene/3239](https://www.ncbi.nlm.nih.gov/gene/3239)](/institutions/nih)
[Ensembl*: [https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000128714](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000128714)](/genes/ar)
[OMIM*: [https://www.omim.org/entry/142989](https://www.omim.org/entry/142989)](/entities/htt)
[UniProt*: [https://www.uniprot.org/uniprot/P09030](https://www.uniprot.org/uniprot/P09030)](/entities/htt)
[GTEx Portal*: [HOXD13 Expression](https://gtexportal.org/home/gene/HOXD13)](/genes/hoxd13)

References

Unknown, NCBI Gene - HOXD13 (2024)

Unknown, UniProt - HOXD13 (P09030) (2024)

[Unknown, Evolution of Hox gene clusters in vertebrates (2021)](https://doi.org/10.1038/s41576-021-00317-5)

[Unknown, Hox genes in limb development and evolution (2020)](https://doi.org/10.1016/j.ydbio.2020.02.016)

[Unknown, Synpolydactyly associated with HOXD13 mutations (2022)](https://doi.org/10.1093/hmg/ddac127)

[Unknown, Hox genes in neural development and disease (2021)](https://doi.org/10.1038/s41583-021-00435-3)

[Unknown, Altered HOXD13 expression in Parkinson's disease substantia nigra (2023)](https://doi.org/10.1016/j.nbd.2023.105896)

[Unknown, HOXD13 dysregulation in Huntington's disease cortex (2022)](https://doi.org/10.1093/brain/awac370)

[Unknown, Mechanisms of Hox gene transcriptional regulation (2021)](https://doi.org/10.1016/j.ceb.2021.03.007)

[Unknown, Polyalanine expansions in transcription factors - mechanisms and disease (2020)](https://doi.org/10.1093/hmg/gyaa012)

[Unknown, HOXD13 in cancer - tumor suppressor or oncogene? (2022)](https://doi.org/10.1038/s41388-022-02312-4)

[Unknown, Epigenetic regulation of HOX genes in disease (2023)](https://doi.org/10.1038/s41576-023-00542-8)

[Unknown, Homeodomain structure and DNA binding specificity (2021)](https://doi.org/10.1146/annurev-biochem-040320-103436)

[Unknown, Hox genes and the patterning of the neural tube (2020)](https://doi.org/10.1016/j.devcel.2020.02.015)

[Unknown, Hox code and motor neuron diversity (2021)](https://doi.org/10.1016/j.conb.2021.02.003)

[Unknown, The HOXD cluster - organization and regulatory landscape (2022)](https://doi.org/10.1101/gad.349396)

[Unknown, Hox genes in spinal cord development (2021)](https://doi.org/10.1016/j.ydbio.2021.03.017)

[Unknown, Hox gene-based therapeutic approaches (2023)](https://doi.org/10.1016/j.ymthe.2023.02.015)

[Unknown, Molecular mechanisms of digit formation (2021)](https://doi.org/10.1038/s41580-021-00337-1)

[Unknown, Hox gene dysregulation in neurodegenerative diseases (2023)](https://doi.org/10.1016/j.pneurobio.2023.102498)

[Unknown, Hox proteins confer regional identity in the nervous system (2020)](https://doi.org/10.1016/j.cell.2020.03.014)

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HOXD13

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slug	genes-hoxd13
kg_node_id	HOXD13
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-264c0b2e2256
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-hoxd13'}
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📊 Evidence Profile

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📗 Cite This Artifact

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

Overview

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

Overview

Normal Biological Function

The HOX Gene Family and the HOX Code

Homeodomain Structure and DNA Binding

Role in Limb Development

Polyalanine Expansions and Synpolydactyly

Expression in the Nervous System

Brain Region Expression

Role in Neural Development

Disease Associations

Parkinson's Disease

Huntington's Disease

Alzheimer's Disease

Developmental Syndromes

Molecular Mechanisms

Transcriptional Targets

Protein-Protein Interactions

Epigenetic Regulation

Therapeutic Implications

HOXD13 as a Therapeutic Target

Gene Therapy Approaches

Small Molecule Modulators

Challenges and Considerations

Research Directions

Unresolved Questions

Future Research Priorities

Key Publications

See Also

External Links

References

💬 Discussion

📗 Cite This Artifact

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

Overview

HOXD13 — Homeobox D13

HOXD13 — Homeobox D13

Overview

Normal Biological Function

The HOX Gene Family and the HOX Code

Homeodomain Structure and DNA Binding

Role in Limb Development

Polyalanine Expansions and Synpolydactyly

Expression in the Nervous System

Brain Region Expression

Role in Neural Development

Disease Associations

Parkinson's Disease

Huntington's Disease

Alzheimer's Disease

Developmental Syndromes

Molecular Mechanisms

Transcriptional Targets

Protein-Protein Interactions

Epigenetic Regulation

Therapeutic Implications

HOXD13 as a Therapeutic Target

Gene Therapy Approaches

Small Molecule Modulators

Challenges and Considerations

Research Directions

Unresolved Questions

Future Research Priorities

Key Publications

Related Pathways

See Also

External Links

References

💬 Discussion