Synthetic Gap Junction Protein Beta 1 (GJb1)

This gene encodes a member of the gap junction protein family. The gap junction proteins are membrane-spanning proteins that assemble to form gap junction channels that facilitate the transfer of ions and small molecules between cells. According to sequence similarities at the nucleotide and amino acid levels, the gap junction proteins are divided into two categories, alpha and beta. Mutations in this gene cause X-linked Charcot-Marie-Tooth disease, an inherited peripheral neuropathy. Alternatively spliced transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Oct 2008]

GJB1: One gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell. Defects in GJB1 are the cause of Charcot-Marie-Tooth disease X-linked type 1 (CMTX1); also designated CMT- X. CMTX1 is a form of Charcot-Marie-Tooth disease, the most common inherited disorder of the peripheral nervous system. Charcot- Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies characterized by severely reduced motor nerve conduction velocities (NCVs) (less than 38m/s) and segmental demyelination and remyelination, and primary peripheral axonal neuropathies characterized by normal or mildly reduced NCVs and chronic axonal degeneration and regeneration on nerve biopsy. CMTX1 has both demyelinating and axonal features. Central nervous system involvement may occur. Defects in GJB1 may contribute to the phenotype of Dejerine-Sottas syndrome (DSS); also known as Dejerine-Sottas neuropathy (DSN) or hereditary motor and sensory neuropathy III (HMSN3). DSS is a severe degenerating neuropathy of the demyelinating Charcot-Marie-Tooth disease category, with onset by age 2 years. DSS is characterized by motor and sensory neuropathy with very slow nerve conduction velocities, increased cerebrospinal fluid protein concentrations, hypertrophic nerve changes, delayed age of walking as well as areflexia. There are both autosomal dominant and autosomal recessive forms of Dejerine- Sottas syndrome. Belongs to the connexin family. Beta-type (group I) subfamily.

Protein type: Channel, misc.; Motility/polarity/chemotaxis; Membrane protein, multi-pass; Membrane protein, integral

Chromosomal Location of Human Ortholog: Xq13.1

Cellular Component: connexon complex; endoplasmic reticulum membrane; integral to membrane

Molecular Function: protein homodimerization activity

Biological Process: nervous system development; cell-cell signaling; gap junction assembly; transport

Disease: Charcot-marie-tooth Disease, X-linked Dominant, 1