Post-transcriptional regulation of fukutin in an astrocytoma cell line

Fukutin is the gene responsible for Fukuyama-type congenital muscular dystrophy (FCMD), an autosomal recessive disease associated with central nervous system (CNS) and eye anomalies. Fukutin is involved in basement membrane formation via the glycosylation of a-dystroglycan (a-DG), and hypoglycosylation of a-DG provokes the muscular, CNS and eye lesions of FCMD. Astrocytes play an important role in the pathogenesis of the CNS lesions, but the post-transcriptional regulation of fukutin mRNA has not been elucidated. In this study, we investigated the characteristics of fukutin mRNA using an astrocytoma cell line that expresses fukutin and glycosylated a-DG. The glycosylation of a-DG was considered to be increased by over-expression of fukutin and decreased by knockdown of fukutin. Knockdown of Musashi-1, one of the RNA-binding proteins involved in the regulation of neuronal differentiation, induced a decrease in fukutin mRNA. Immunoprecipitation and ELISA-based RNA-binding assay demonstrated possible binding between fukutin mRNA and Musashi-1 protein. A relationship between fukutin mRNA and vimentin protein was also proposed. In situ hybridization for fukutin mRNA showed a positive cytoplasmic reaction including cytoplasmic processes. From these results, fukutin mRNA is suggested to be a localized mRNA up-regulated by Musashi-1 and to be a component of a mRNA-protein complex which includes Musashi-1 and (presumably) vimentin proteins.