Dystroglycan mRNA expression during normal and mdx mouse embryogenesis: a comparison with utrophin and the apo-dystrophins.

Alpha dystroglycan (156 kDa DAG) and beta dystroglycan (43 kDa DAG) are encoded by the same gene and are components of the dystrophin-associated membrane glycoprotein complex. The dystroglycans together with dystrophin form a link between the extracellular matrix and the intracellular cytoskeleton of the muscle fibre. Using in situ hybridisation to mRNA in embryo sections we have examined the expression of the mouse dystroglycan gene. Dystroglycan transcripts are ubiquitously expressed throughout development but are most abundant in cardiac, skeletal and smooth muscle and in ependymal cells lining the developing neural tube and brain. The expression patterns of dystroglycan and dystrophin overlap in major muscle systems during development, suggesting that the dystrophin-dystroglycan complex plays an important role during myogenesis. In contrast, the major sites of utrophin expression do not co-localize with those of dystroglycan suggesting that utrophin may interact with a distinct membrane-associated complex in these non-muscle sites. In mdx embryos the pattern of distribution of dystroglycan mRNA remains unchanged, as do those of utrophin and apo-dystrophin mRNAs. This observation implies that the observed changes in the relative abundance of DAGs and utrophin in dystrophin-deficient muscle occur post-transcriptionally.