Systematic Review of Phenotypical Characteristics of P51S COCH Mutation

Gene mutations account for more than 60% of congenital sensorineural hearing loss (SNHL) in Western Countries. Hereditary SNHL does not necessarily start at birth, however, as many causative gene mutations only begin to express at much later ages, such as for example DFNA9, also known as the ninth discovered autosomal dominant SNHL. It is characterized by a late onset of rapid progressive SNHL together with accompanying vestibular impairment. The first reported DFNA9 patients were carrying the c.151 C\>T mutation in COCH, which is the result of a substitution of cytosine by thymine nucleotide of the 151th base pair (c.151C\>T). At protein level, this missense point mutation induces a mistranslation to a serine instead of a proline amino-acid (p.Pro51Ser, (P51S)), producing mutant cochlin that cause a dominant negative effect due to misfolding. In the perspective of promising future hearing and vestibular treatment developments, such as gene therapy, stem cell therapy, neural regeneration, in association with cochlear and/or vestibular implantation, a more accurate understanding of the onset of the very first signs of the auditory and vestibular deterioration is important. However, in early stages these first signs of impairment are very discrete and pre-symptomatic. The aim of this systematic review is to identify studies related to DFNA9, caused by the P51S COCH variant, describing detailed genotype-phenotype correlation in relation to the age and to investigate the age of onset of the SNHL and peripheral vestibular function as well as their progression in relation to age.