Expression pattern of the mouse ortholog of the Pendred's syndrome gene (Pds) suggests a key role for pendrin in the inner ear.
Pendred's syndrome is an autosomal-recessive disorder characterized by deafness and goiter. After our recent identification of the human gene mutated in Pendred's syndrome (PDS), we sought to investigate in greater detail the expression of the gene and the function of its encoded protein (pendrin). Toward that end, we isolated the corresponding mouse ortholog (Pds) and performed RNA in situ hybridization on mouse inner ears (from 8 days postcoitum to postnatal day 5) to establish the expression pattern of Pds in the developing auditory and vestibular systems. Pds expression was detected throughout the endolymphatic duct and sac, in distinct areas of the utricle and saccule, and in the external sulcus region within the cochlea. This highly discrete expression pattern is unlike that of any other known gene and involves several regions thought to be important for endolymphatic fluid resorption in the inner ear, consistent with the putative functioning of pendrin as an anion transporter. These studies provide key first steps toward defining the precise role of pendrin in inner ear development and elucidating the pathogenic mechanism for the deafness seen in Pendred's syndrome.