TMC1

The TMC1 gene provides instructions for making a protein called transmembrane channel-like 1. This protein is found in the inner ear, but its function is not fully understood. Based on its location in the inner ear, the TMC1 protein probably plays a role in converting sound waves to nerve impulses, a critical process for normal hearing. Alternatively, the TMC1 protein may be involved in signalling processes that are important for the survival of cells in the inner ear.

nonsyndromic deafness - caused by mutations in the TMC1 gene

Researchers have identified several TMC1 mutations that cause a form of nonsyndromic deafness (hearing loss without related signs and symptoms affecting other parts of the body) called DFNB7/B11. This form of deafness is inherited in an autosomal recessive manner, which means that two copies of the TMC1 gene in each cell are altered. Some TMC1 mutations create a premature stop signal in the instructions for making the TMC1 protein. As a result, researchers believe that no protein is produced or an abnormally small protein is made. Other mutations delete part of the TMC1 gene. A few mutations replace one of the building blocks (amino acids) used to make the TMC1 protein with an incorrect amino acid. This type of mutation may alter the 3-dimensional shape of the TMC1 protein. TMC1 mutations that cause autosomal recessive deafness probably affect the normal activity of the TMC1 protein and disrupt the conversion of sound waves to nerve impulses.

One TMC1 mutation has been reported in individuals with a form of nonsyndromic deafness called DFNA36, which is inherited in an autosomal dominant manner. This type of inheritance means that one copy of an altered TMC1 gene in each cell is sufficient to cause hearing loss. The mutation replaces the amino acid aspartic acid with the amino acid asparagine at protein position 572 (written as Asp572Asn or D572N). This mutation probably affects the normal activity of the TMC1 protein and disrupts the conversion of sound waves to nerve impulses.