Positional cloning of hereditary deafness genes is a direct approach to identify molecules and mechanisms underlying auditory function. Here we report a locus for dominant deafness, DFNA36, which maps to human chromosome 9q13-21 in a region overlapping the DFNB7/B11 locus for recessive deafness. We identified eight mutations in a new gene, transmembrane cochlear-expressed gene 1 (TMC1), in a DFNA36 family and eleven DFNB7/B11 families. We detected a 1.6-kb genomic deletion encompassing exon 14 of Tmc1 in the recessive deafness (dn) mouse mutant, which lacks auditory responses and has hair-cell degeneration. TMC1 and TMC2 on chromosome 20p13 are members of a gene family predicted to encode transmembrane proteins. Tmc1 mRNA is expressed in hair cells of the postnatal mouse cochlea and vestibular end organs and is required for normal function of cochlear hair cells.

We ascertained a large American family with an autosomal dominant form of progressive non-syndromic sensorineural hearing loss. After excluding linkage to known deafness loci, we performed a genome-wide scan and found linkage to marker GAAT1A4 on chromosome 8q22 (LOD=5.12 at ????=0), and this locus was designated DFNA28. Sequencing of six candidate genes in the 1.4 cM linked region identified a frameshift mutation (1609–1610insC) resulting in a premature translation stop codon in exon 14 of the gene TFCP2L3 (transcription factor cellular promoter 2-like 3). TFCP2L3 is a member of a family of transcription factor genes whose archetype is TFCP2, a mammalian homolog of the Drosophila gene grainyhead. Northern blot analyses and in situ hybridization studies show that mouse Tfcp2l3 is expressed in many epithelial tissues, including cells lining the cochlear duct, at embryonic day 18.5 and postnatal day 5.