Mutation analysis of COL9A3, a gene highly expressed in the cochlea, in hearing loss patients.

cDNA microarray analysis indicated that COL9A3 is one of the highly expressed genes in the cochlea. This suggests that collagen type IX has a crucial functional role in the inner ear and may be a candidate gene for hearing loss. Mutation analysis was carried out to find possible disease-causing mutations in this gene. The direct-sequencing method was applied to the COL9A3 gene in 159 non-syndromic sensorineural deafness patients and 150 normal controls. Two possible disease-causing mutations were identified: an in-frame deletion of three amino acid residues (G181-P183 del) and a missense mutation (D617E). The patients with the mutations showed a moderate progressive bilateral sensorineural hearing impairment in all frequencies. The present data indicate that mutations of COL9A3 may cause non-syndromic hearing impairment.