RESUMO
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.
Assuntos
Proteínas de Transporte/genética , Cóclea/metabolismo , Genômica , Perda Auditiva/genética , Canais de Potássio/genética , Animais , Northern Blotting/métodos , Western Blotting/métodos , Encéfalo/metabolismo , Mapeamento Cromossômico/métodos , Análise Mutacional de DNA/métodos , Humanos , Imuno-Histoquímica/métodos , Rim/metabolismo , Camundongos , Estrutura Molecular , Cadeias Pesadas de Miosina , Miosina Tipo II , Canais de Potássio/metabolismo , Canais de Potássio de Domínios Poros em Tandem , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodosRESUMO
Neuroepithelial cysts are lesions of the central nervous system that have previously been reported in cerebral parenchyma, in the spinal cord, and within the ventricles in association with the choroid plexus. We describe 2 cases of neuroepithelial cysts of the middle ear. One was diagnosed after surgery for a retraction pocket and chronic otitis media complicated by an intraoperative cerebrospinal fluid (CSF) leak. The other produced bilateral spontaneous CSF otorrhea and mimicked the presentation of arachnoid granulations. Both cases were verified with immunohistochemical stains. Neuroepithelial cysts, although rare, should be considered in the differential diagnosis of spontaneous CSF otorrhea or an epitympanic mass.
