Abstract
Deafness in vertebrates is associated with variants of hundreds of genes. Yet, many mutant genes causing rare forms of deafness remain to be discovered. A consanguineous Pakistani family segregating nonsyndromic deafness in two sibships were studied using microarrays and exome sequencing. A 1.2 Mb locus (DFNB128) on chromosome 5q11.2 encompassing six genes was identified. In one of the two sibships of this family, a novel homozygous recessive variant NM_005921.2:c.4460G>A p.(Arg1487His) in the kinase domain of MAP3K1 co-segregated with nonsyndromic deafness. There are two previously reported Map3k1-kinase-deficient mouse models that are associated with recessively inherited syndromic deafness. MAP3K1 phosphorylates serine and threonine and functions in a signaling pathway where pathogenic variants of HGF, MET, and GAB1 were previously reported to be associated with human deafness DFNB39, DFNB97, and DFNB26, respectively. Our single-cell transcriptome data of mouse cochlea mRNA show expression of Map3k1 and its signaling partners in several inner ear cell types suggesting a requirement of wild-type MAP3K1 for normal hearing. In contrast to dominant variants of MAP3K1 associated with Disorders of Sex Development 46,XY sex-reversal, our computational modeling of the recessive substitution p.(Arg1487His) predicts a subtle structural alteration in MAP3K1, consistent with the limited phenotype of nonsyndromic deafness.