title: Genomic structure, cochlear expression, and mutation screening of KCNK6, a candidate gene for DFNA4.
abstract: KCNK6 encodes a tandem pore domain potassium channel, TWIK-2, that maps to chromosome 19. Both STS and linkage maps established KCNK6 as a positional candidate gene for DFNA4, a form of autosomal dominant nonsyndromic hereditary hearing loss. Identification and characterization of Kcnk6 expression within the mammalian cochlea established the gene as a functional candidate for DFNA4. Identification of Twik-2 expression in the mouse cochlea was initially established via RT-PCR assay of cochlear RNA. Subsequent immunoblot analysis of cochlear homogenate yielded a distinct 35-kDa band corresponding to the calculated molecular weight of the mouse Twik-2. Immunohistochemical studies localized Twik-2 expression in the cochlea predominantly within the stria vascularis. This vascular tissue borders the cochlear duct and is a critical regulator of potassium concentration in the endolymph. Genomic structure of TWIK-2 was subsequently determined and shown to consist of three coding exons with splice acceptor and donor sites in accordance with the consensus GT-AG rule. Two separate DFNA4 families were screened for KCNK6 sequence alterations. No mutations were found, thus excluding TWIK-2 as the DFNA4 candidate disease gene. Nevertheless, expression of Twik-2 within the stria vascularis suggests a potential role for this protein as one of the terminal components of the potassium ion-recycling pathway that contributes toward its reabsorption into the endolymph.
authors.affiliation: Laboratory of Molecular Genetics, Epstein Laboratories, Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, California, USA. amhatre@med.nyu.edu
authors.forename: Anand N
authors.initials: AN
authors.lastname: Mhatre
authors.forename: Jiang
authors.initials: J
authors.lastname: Li
authors.forename: Arthur F
authors.initials: AF
authors.lastname: Chen
authors.forename: C Spencer
authors.initials: CS
authors.lastname: Yost
authors.forename: Richard J H
authors.initials: RJ
authors.lastname: Smith
authors.forename: Christoph H
authors.initials: CH
authors.lastname: Kindler
authors.forename: Anil K
authors.initials: AK
authors.lastname: Lalwani
mesh_terms: D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics*; D002874:Chromosome Mapping / Q000379:methods; D003051:Cochlea / Q000378:metabolism*; D004252:DNA Mutational Analysis / Q000379:methods; D023281:Genomics; D034381:Hearing Loss / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007668:Kidney / Q000378:metabolism; D051379:Mice; D015394:Molecular Structure; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
chemical_list: D002352:Carrier Proteins; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C118290:KCNK6 protein, human; C492208:Kcnk6 protein, mouse; C477830:MYH7b protein, human