Heparan sulfate (HS) is a sulfated linear polysaccharide around cell surface. HS is involved in various physiological processes. Recent studies revealed that lack of HS induced autism-like behaviors and hyperglycemia. However, the roles of HS in skeletal muscles remained to be elucidated.
First, we examined the role of HS in the differentiation of muscle cells using C2C12 cells, a mouse myoblast cell line. CRISPR/CAS9 technology was used to delete Ext1, which encodes a heparan sulfate synthase, to generate a HS-deleted C2C12 cell line. HS deletion dramatically impaired myoblast differentiation, demonstrating the essential role of HS in myoblast differentiation. Next, we generated skeletal muscle-specific Ext1 deleted mice (cKO). Muscle weakness of cKO was revealed in treadmill tests and wire hang tests. Histochemical analysis of skeletal muscles revealed that the cross sectional area of each muscle was smaller in cKO. Electromicroscopic observation showed that myofibrils were thinner in cKO. Finally, we examined muscle differentiation after muscle injury Myosin heavy chain expression, one of the marker proteins for muscle differentiation, was significantly decreased in cKO muscles. These results demonstrate that HS plays an important role in skeletal muscle, especially in differentiation.