Disease-specific differences in glycosylation of mouse and human skeletal muscle
Proper glycosylation of proteins at the muscle cell membrane, or sarcolemma, is critical for proper muscle function. The laminin receptor alpha-dystroglycan (α-DG) is heavily glycosylated and mutations in 24 genes involved in proper α-DG glycosylation have been identified as causing various forms of congenital muscular dystrophy. While work over the past decade has elucidated the structure bound by laminin and the enzymes required for its creation, very little is known about muscle glycosylation outside of α-DG glycosylation. The modification of glycan structures with terminal GalNAc residues at the rodent neuromuscular junction (NMJ) has remained the focus of work in mouse muscle glycosylation, while qualitative lectin histochemistry studies performed three decades ago represent the majority of human muscle glycosylation research.
This thesis quantifies differentiation-, species-, and disease-specific differences in mouse and human skeletal muscle glycosylation. Following differentiation of mouse myotubes, increased binding was found of lectins specific for GalNAc and O-glycans. Additionally, analysis of binding preferences of four GalNAc-specific lectins, which historically have been used to identify the rodent NMJ, identified differences in the glycan types bound on distinct glycoproteins by each lectin. Following differentiation of human myotubes, specific increases in binding of high mannose N-glycan specific lectin NPA, asialo core 1 O-glycan specific lectin PNA, α2,3-linked sialic acid specific lectin MAA-II and GalNAc specific lectin WFA were observed. Disease-specific differences in binding of NPA, Jac (sialylated core 1 O-glycans), TJA-I (α2,3-linked sialic acid) and WFA were observed quantitatively when comparing binding to healthy and dystrophic myotubes as well as qualitatively via lectin staining of healthy and dystrophic human skeletal muscle tissue sections. This work provides the first quantitative characterization of mouse and human muscle glycosylation, identifies lectin biomarkers for differentiation-, species-, and disease-specific differences in mouse and human muscle glycosylation, and lays the groundwork for future studies which further our understanding of the relationship between proper muscle glycosylation and muscle function.