Hearing impairment in mice with the cmd/cmd (cartilage matrix deficiency) mutant gene

Mice homozygous for the autosomal recessive gene cartilage matrix deficiency (cmd) are afflicted with lesions involving cartilaginous tissue which give rise to, among other things, marked hearing loss as evidenced by auditory evoked potentials. Ultrastructural studies of the inner ear reveal that while inner hair cells are normal in shape and content, the outer hair cells have disappeared and there is some debris in Nuel's space. The pillar cells are normal as are the stria vascularis, basilar membrane, and tectorial membrane. We conclude that the cmd gene, thought to be vital in the regulation of proteoglycan synthesis, is responsible for the hearing impairment and structural anomalies of the cochlea seen in these mutant, homozygous mice.