Genetic variant behind cause of adult deafness

Thousands of adults are at risk of deafness because of a common inherited genetic variant, researchers report today.

Dutch researchers, reporting in the latest edition of the Journal of Medical Genetics says their discovery makes it an ideal candidate for gene therapy.

So far, 118 genes have been associated with the heritable form of deafness and variants within these genes are behind many types of congenital and childhood deafness.

However, the variants do not explain adult deafness, even though between 30% and 70% of hearing loss in adults is believed to be inherited.

The researchers had already discovered the chromosomal region involved in hearing loss in one family, but not the gene involved, so the family members who had hearing loss in one or both ears underwent gene sequencing.

This revealed a missing section of the RIPOR2 gene in 20 of the 23 family members with confirmed hearing loss. The genetic variant was also found in three other family members, aged 23, 40, and 51, who did not yet have any hearing loss.

This prompted the researchers to carry out gene sequencing in a further 11 families affected by hearing loss, and the genetic variant was found in 39 of 40 family members with confirmed hearing loss as well as in two people aged 49 and 50 who were not affected by hearing loss.

The RIPOR2 genetic variant was found in a further 18 out of 22,952 randomly selected people for whom no information on hearing loss was available.

The research team found that four family members with hearing loss did not have the RIPOR2 genetic variant, which meant their deafness could have been associated with heavy smoking or other genetic abnormalities.

The team suggests that the prevalence of genetic-induced hearing loss means that it is common and they estimate in The Netherlands alone the RIPOR2 genetic variant is likely present “in more than 13,000 individuals who are therefore at risk of developing [hearing loss] or who have developed [hearing loss] already due to this variant”.

“Because of the large number of subjects estimated to be at risk for [hearing loss] due to the c.1696_1707 del RIPOR2 variant, it is an attractive target for the development of a genetic therapy,” they conclude.

De Bruijn SE, Smits JJ, Liu C et al. An RIPOR2 in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss. Journal of Medical Genetics. July 2020. doi 10.1136.jmedgenet-2020-106863

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