Characterization of δ-sarcoglycan, a novel component of the oligomeric sarcoglycan complex involved in limb-girdle muscular dystrophy

The sarcoglycan complex is known to be involved in limb-girdle muscular dystrophy (LGMD) and is composed of at least three proteins: α-, β-, and γ-sarcoglycan. δ-Sarcoglycan has now been identified as a second 35-kDa sarcolemmal transmembrane glycoprotein that shares high homology with γ- sarcoglycan and is expressed mainly in skeletal and cardiac muscle. Biochemical analysis has demonstrated that γ- and δ-sarcoglycan are separate entities within the sarcoglycan complex and that all four sarcoglycans exist in the complex on a stoichiometrically equal basis. Immunohistochemical analysis of skeletal muscle biopsies from patients with LGMD2C, LGMD2D, and LGMD2E demonstrated a reduction of the entire sarcoglycan complex in these muscular dystrophies. Furthermore, we have mapped the human δ-sarcoglycan gene to chromosome 5q33-q34 in a region overlapping the recently linked autosomal recessive LGMD2F locus.