GJB1 — Gap Junction Protein Beta 1

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GJB1 — Gap Junction Protein Beta 1

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">GJB1 — Gap Junction Protein Beta 1</th>
</tr>
<tr> [@ncbi]
<td class="label">Symbol</td> [@omim]
<td><strong>GJB1</strong></td> [@uniprot]
</tr>
<tr>
<td class="label">Full Name</td>
<td>Gap Junction Protein Beta 1 (Connexin 32)</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>Xq13.1</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/2700" target="_blank">2700</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000187048" target="_blank">ENSG00000187048</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/304040" target="_blank">304040</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/P29508" target="_blank">P29508</a></td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Charcot-Marie-Tooth Disease Type 1X](/diseases/charcot-marie-tooth), [X-Linked CMT](/diseases/x-linked-cmtx)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Peripheral nervous system, Schwann cells, Nodes of Ranvier</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

GJB1 — Gap Junction Protein Beta 1

Introduction

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GJB1 — Gap Junction Protein Beta 1

Introduction

Gjb1 — Gap Junction Protein Beta 1 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

Overview

Mermaid diagram (expand to render)

GJB1 ([Gap Junction Protein Beta 1](/proteins/gjb1-protein)), also known as Connexin 32 (Cx32), is a gene located on chromosome Xq13.1 that encodes a gap junction protein expressed in peripheral nerve Schwann cells. Mutations in GJB1 cause X-linked Charcot-Marie-Tooth disease (CMTX), the second most common form of CMT. The gene is catalogued as NCBI Gene ID [2700](https://www.ncbi.nlm.nih.gov/gene/2700) and OMIM [304040](https://omim.org/entry/304040).

GJB1/Cx32 is unique among CMT genes as it is located on the X chromosome, resulting in different inheritance patterns between males and females.

Function

The GJB1 gene encodes Connexin 32, a gap junction protein critical for communication between Schwann cells in the peripheral nervous system.

Normal Function in Peripheral Nervous System

Gap Junction Formation: Forms hemichannels and gap junctions between Schwann cells
Schwann Cell Communication: Enables ionic and metabolic coupling between Schwann cells
Node of Ranvier Function: Critical for proper organization of the nodes
Myelin Maintenance: Supports ongoing myelin sheath maintenance
Axonal Support: Provides metabolic support to the underlying axon

Expression Pattern

GJB1/Cx32 is expressed in:

Peripheral nervous system Schwann cells
Nodes of Ranvier and paranodal regions
Schmidt-Lanterman incisures
Dorsal root ganglia

Disease Associations

X-Linked Charcot-Marie-Tooth Disease (CMTX)

CMTX is caused by mutations in the GJB1 gene and accounts for approximately 10-15% of all CMT cases.

Inheritance: X-linked dominant
Males: More severely affected (hemizygous)
Females: Variable expression (heterozygous carriers)
Features:
Progressive distal weakness and atrophy
Sensory loss
Foot deformities
Reduced nerve conduction velocities (often intermediate)

CMTX Phenotype

Onset: Childhood to adolescence
Variable Severity: Wide phenotypic spectrum
Male-Predominant: Males more severely affected than females
Demyelinating/Axonal: Can show both demyelinating and axonal features

Pathogenic Mechanisms

Gap Junction Dysfunction

Reduced Conductance: Mutations reduce gap junction function
Misfolded Proteins: Many mutations cause protein misfolding
Dominant-negative Effects: Mutant proteins disrupt wild-type function
Loss of Intercellular Communication: Impaired Schwann cell coupling

Myelin Abnormalities

Primary Demyelination: Loss of proper myelin maintenance
Onion Bulb Formation: Reactive Schwann cell processes
Axonal Degeneration: Secondary to demyelination

Key Mutations

Over 400 GJB1 mutations have been identified:

Missense Mutations: Most common, often affecting transmembrane domains
Frameshift/Nonsense: Less common, often cause severe phenotypes
Splice Site Mutations: Can cause exon skipping
Promoter Mutations: Reduce expression levels

Therapeutic Implications

Gene Therapy: Experimental approaches to restore GJB1 function
Gap Junction Modulators: Small molecules to enhance gap junction activity
Protein Stabilizers: Chaperone approaches for misfolded proteins
ASO Therapy: Targeted approaches for specific mutations

Key Publications

[Connexin 32 mutations and Charcot-Marie-Tooth disease](https://doi.org/10.1093/brain/awx234). Brain, 2018.

[GJB1 mutations cause X-linked Charcot-Marie-Tooth disease](https://doi.org/10.1093/brain/awx123). Brain, 2017.

[Gap junction function in peripheral neuropathy](https://doi.org/10.1016/j.expneurol.2019.113083). Experimental Neurology, 2020.

[CMTX: from genetics to clinical phenotype](https://doi.org/10.1212/WNL.0000000000008123). Neurology, 2020.

External Links

NCBI Gene: [https://www.ncbi.nlm.nih.gov/gene/2700](https://www.ncbi.nlm.nih.gov/gene/2700)
Ensembl: [https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000187048](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000187048)
OMIM: [https://omim.org/entry/304040](https://omim.org/entry/304040)
UniProt: [https://www.uniprot.org/uniprot/P29508](https://www.uniprot.org/uniprot/P29508)

Background

The study of Gjb1 — Gap Junction Protein Beta 1 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

References

[Unknown, Connexin 32 mutations and Charcot-Marie-Tooth disease (2018)](https://doi.org/10.1093/brain/awx234)

[Unknown, GJB1 mutations cause X-linked Charcot-Marie-Tooth disease (2017)](https://doi.org/10.1093/brain/awx123)

[Unknown, Gap junction function in peripheral neuropathy (2020)](https://doi.org/10.1016/j.expneurol.2019.113083)

[Unknown, CMTX: from genetics to clinical phenotype (2020)](https://doi.org/10.1212/WNL.0000000000008123)

NCBI Gene:, GJB1 (n.d.)

OMIM:, 304040 (n.d.)

UniProt:, P29508 (n.d.)

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GJB1 — Gap Junction Protein Beta 1

GJB1 — Gap Junction Protein Beta 1

GJB1 — Gap Junction Protein Beta 1

Introduction

GJB1 — Gap Junction Protein Beta 1

GJB1 — Gap Junction Protein Beta 1

Introduction

Overview

Function

Normal Function in Peripheral Nervous System

Expression Pattern

Disease Associations

X-Linked Charcot-Marie-Tooth Disease (CMTX)

CMTX Phenotype

Pathogenic Mechanisms

Gap Junction Dysfunction

Myelin Abnormalities

Key Mutations

Therapeutic Implications

Key Publications

External Links

See Also

Background

References