Many proteins necessary for sound transduction have been identified through positional cloning of genes that cause deafness(1-3). We report here that mutations of LRTOMT are associated with profound nonsyndromic hearing loss at the DFNB63 locus on human chromosome 11q13.3-q13.4. LRTOMT has two alternative reading frames and encodes two different proteins, LRTOMT1 and LRTOMT2, detected by protein blot analyses. LRTOMT2 is a putative methyltransferase. During evolution, new transcripts can arise through partial or complete coalescence of genes(4). We provide evidence that in the primate lineage LRTOMT evolved from the fusion of two neighboring ancestral genes, which exist as separate genes (Lrrc51 and Tomt) in rodents.