1. Connexin 26

Connexin is a protein of communicating junctions.

The presence of this mutated gene corresponds to 30% of deafness of children, and is one of the most common genetic abnormalities. It is as common as cystic fibrosis. The mutation in the Connexin 26 gene causes all degrees of deafness. The Connexin 26 gene is located on human chromosome 13.

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The link between the Connexin 26 gene and deafness was discovered and established in 1999 by David Kessel in London. The Connexin 26 gene mutation is an isolated form of congenital deafness.

Isolated congenital deafness is deafness that appears before birth without a family history, that is to say that the newborn can be deaf before birth without his parents being, following a recessive transmission of the responsible gene. Parents carry an abnormal copy of the gene (without knowing it because this copy cannot be expressed) and a normal copy of the gene that makes the inner ear work without reaching the balance of the inner ear. The inner ear has two parts: the cochlea which allows mechanical transduction, and changes the sound vibrations into an electric flow; and the vestibule which allows you to stay properly upright during a movement, allowing us to have a correct balance during translational and rotary movements.

This gene (GJB2) is responsible for the production of a protein called connexin 26. This protein is active in intercellular junctions (and not directly in ciliated cells), especially in the cochlea and it plays a role in recycling certain molecules essential (including potassium) for the functioning of neurosensory cells.

The cochlea is a hollow snail-shaped organ filled with a liquid called the endolymph. The cochlea constitutes the last stage of the integration of sound before the auditory nerve.

3-5% of the general population have an abnormality in this gene and can therefore give birth to children with deafness (if their spouse also has an abnormality in this gene).

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