RESUMO
Mutations at the waltzer (v) locus result in deafness and vestibular dysfunction due to degeneration of the neuroepithelium within the inner ear. Here, we use a positional cloning approach to show that waltzer encodes a novel cadherin (Cdh23), which is most closely related to the Drosophila Fat protein. A single nucleotide deletion in the v(J) allele and a single nucleotide insertion in the v allele are predicted to truncate each protein near the N-terminus and produce a functional null allele. In situ hybridization analysis showed that Cdh23 is expressed in the sensory hair cells of the inner ear, where it has been suggested to be a molecule critical for crosslinking of the stereocilia. In addition, Cdh23 is expressed in the urticulo-saccular foramen,the ductus reuniens, and Reissner's membrane, suggesting that Cdh23 may also be involved in maintaining the ionic composition of the endolymph. Finally, mutations in human CDH23 have recently been described for two loci, DFNB12 and USH1D, which cause nonsyndromic deafness, identifying waltzer as a mouse model for human hearing loss.
Assuntos
Caderinas/genética , Surdez/genética , Mutação , Alelos , Sequência de Aminoácidos , Animais , Proteínas Relacionadas a Caderinas , Caderinas/biossíntese , Mapeamento Cromossômico , Cromossomos Artificiais Bacterianos , Cromossomos Artificiais de Levedura , Clonagem Molecular , Cruzamentos Genéticos , DNA Complementar/metabolismo , Surdez/metabolismo , Drosophila , Biblioteca Gênica , Humanos , Hibridização In Situ , Proteínas de Membrana/genética , Camundongos , Camundongos Mutantes , Modelos Genéticos , Dados de Sequência Molecular , Mapeamento Físico do Cromossomo , Mutação Puntual , Polimorfismo Genético , Polimorfismo de Fragmento de Restrição , Estrutura Terciária de Proteína , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Distribuição TecidualRESUMO
The Rad51 protein has been shown to play a vital role in the DNA repair process. In humans, its interaction with proteins like BRCA1 and BRCA2 has provided an insight into the mechanism of how these molecules function as tumor suppressors. Several members of the Rad51-like family have been recently identified, including RAD51L2. This gene has been found to be amplified in breast tumors suggesting its role in tumor progression. Here, we describe the cloning of the murine homologue of the human RAD51L2/RAD51C gene. Sequence analysis has revealed that the murine Rad51l2 protein is 86% identical and 93% similar to its human homologue. In spite of such high sequence conservation, the murine protein lacks the first nine amino acids present in the human protein. We have cloned and confirmed the sequence of the 5' end of the murine Rad51l2 cDNA using 5' RACE technique as well as by sequencing the genomic region flanking the first exon of the murine Rad51l2 gene. Northern analysis shows that Rad51l2 is expressed in several adult tissues as well as in embryos at various developmental stages. The murine Rad51l2 gene maps to chromosome 11 and is located in the syntenic region of human chromosome 17q22-23, where the human RAD51L2 is present.