Dystroglycan and ProteinO-Mannosyltransferases 1 and 2 Are Required to Maintain Integrity ofDrosophilaLarval Muscles

Abstract

In vertebrates, mutations in Protein O-mannosyltransferase1 (POMT1) or POMT2 are associated with muscular dystrophy due to a requirement for O-linked mannose glycans on the Dystroglycan (Dg) protein. In this study we examine larval body wall muscles of Drosophila mutant for Dg, or RNA interference knockdown for Dg and find defects in muscle attachment, altered muscle contraction, and a change in muscle membrane resistance. To determine if POMTs are required for Dg function in Drosophila, we examine larvae mutant for genes encoding POMT1 or POMT2. Larvae mutant for either POMT, or doubly mutant for both, show muscle attachment and muscle contraction phenotypes identical to those associated with reduced Dg function, consistent with a requirement for O-linked mannose on Drosophila Dg. Together these data establish a central role for Dg in maintaining integrity in Drosophila larval muscles and demonstrate the importance of glycosylation to Dg function in Drosophila. This study opens the possibility of using Drosophila to investigate muscular dystrophy.

N-glycosylation requirements in neuromuscular synaptogenesis

“…1D) (Desai et al, 1994;Beumer et al, 2002). Similarly, Dystroglycan (DG) is reportedly the primary substrate for VVA labeling at the NMJ (Haines et al, 2007;Nakamura et al, 2010). Both HRP and VVA labeling are absent at Mgat1 null NMJs (Fig.…”

“…For example, the widely employed anti-HRP antibody binds fucosylated N-glycans in the presynaptic membrane, which require Mgat1 for fucose modification (Sarkar et al, 2006). Likewise, VVA lectin is a synaptic glycan marker at the Drosophila NMJ, which reportedly recognizes primarily postsynaptic Dystroglycan (Haines et al, 2007;Rushton et al, 2012). The endogenous MTG lectin patterns the extracellular glycosylated synaptomatrix (Rohrbough et al, 2007), modulates trans-synaptic signaling and is essential for functional synaptogenesis (Rushton et al, 2009;Rohrbough and Broadie, 2010).…”

In vivo analyzes of dystroglycan function during somitogenesis in Xenopus laevis

“…In Drosophila, Dg has been reported to play a fundamental role for polarizing the epithelial cells and the oocytes in the ovaries (Deng et al, 2003). In larval body wall muscles, errors in muscle attachment, muscle contraction, and muscle membrane resistance have been associated with Dg mutant alleles and RNAi mediated reduction of Dg (Haines et al, 2007). Originally, Dg was isolated from skeletal muscle membranes and was found to be an essential component of the dystrophin-glycoprotein complex, which links the ECM surrounding myofibers to the actin cytoskeleton.…”

Biosynthetic Pathway of O-Mannosyl Glycan in Mammals

“…O-Mannosylation is essential for maintaining cell shape and cell integrity (21) and contributes to quality control of proteins in the endoplasmic reticulum (ER) in yeast (22,23). Reduction of protein O-mannosyltransferases in Drosophila melanogaster resulted in defects in embryonic muscle development (24)(25)(26)(27) and pomt1 deletion in mouse resulted in embryonic death (28). Recently, we also demonstrated that O-mannosyltranserase was required for muscle development in zebrafish (29).…”