A novel recessive mutation in OXR1 is identified in patient with hearing loss recapitulated by the knockdown zebrafish.

Hereditary hearing loss is a highly genetically heterogeneous disorder. More than 150 genes have been identified to link to human non-syndromic hearing impairment. To identify genetic mutations and underlying molecular mechanisms in affected individuals and families with congenital hearing loss, we recruited a cohort of 389 affected individuals in 354 families for whole-exome sequencing analysis. In this study, we report a novel homozygous missense variant (c.233A > G, p.Lys78Arg) in the OXR1 gene, which was identified in a 4-year-old girl with sensorineural hearing loss. OXR1 encodes Oxidation Resistance 1 and is evolutionarily conserved from zebrafish to human. We found that the ortholog oxr1b gene is expressed in the statoacoustic ganglion (SAG, a sensory ganglion of ear) and posterior lateral line ganglion (pLL) in zebrafish. Knockdown of oxr1b in zebrafish resulted in a significant developmental defect of SAG and pLL. This phenotype can be rescued by co-injection of wild-type human OXR1 mRNAs, but not mutant OXR1 (c.233A > G) mRNAs. OXR1-associated pathway analysis revealed that mutations of TBC1D24, a TLDc-domain-containing homolog gene of OXR1, have previously been identified in patients with hearing loss. Interestingly, mutations or knockout of OXR1 interacting molecules such as ATP6V1B1 and ESR1 are also associated with hearing loss in patients or animal models, hinting an important role of OXR1 and associated partners in cochlear development and hearing function.