Abstract
Auditory synaptopathy/neuropathy (AS/AN) is a distinct type of sensorineural hearing loss in which the cochlear sensitivity to sound (i.e. active cochlear amplification by outer hair cells) is preserved whereas sound encoding by inner hair cells and/or auditory nerve fibers is disrupted owing to genetic or environmental factors. Autosomal-dominant auditory neuropathy type 2 (AUNA2) was linked either to chromosomal bands 12q24 or 13q34 in a large German family in 2017. By whole-genome sequencing, we now detected a 5500 bp deletion in ATP11A on chromosome 13q34 segregating with the phenotype in this family. ATP11A encodes a P-type ATPase that translocates phospholipids from the exoplasmic to the cytoplasmic leaflet of the plasma membrane. The deletion affects both isoforms of ATP11A and activates a cryptic splice site leading to the formation of an alternative last exon. ATP11A carrying the altered C-terminus loses its flippase activity for phosphatidylserine. Atp11a is expressed in fibers and synaptic contacts of the auditory nerve and in the cochlear nucleus in mice, and conditional Atp11a knockout mice show a progressive reduction of the spiral ganglion neuron compound action potential, recapitulating the human phenotype of AN. By combining whole-genome sequencing, immunohistochemistry, in vitro functional assays and generation of a mouse model, we could thus identify a partial deletion of ATP11A as the genetic cause of AUNA2.