Gamma-sarcoglycan is a protein that in humans is encoded by the SGCGgene.[5][6] The α to δ-sarcoglycans are expressed predominantly (β) or exclusively (α, γ and δ) in striated muscle.[7] A mutation in any of the sarcoglycan genes may lead to a secondary deficiency of the other sarcoglycan proteins, presumably due to destabilisation of the sarcoglycan complex.[8] The disease-causing mutations in the α to δ genes cause disruptions within the dystrophin-associated protein (DAP) complex in the muscle cell membrane.[9] The transmembrane components of the DAP complex link the cytoskeleton to the extracellular matrix in adult muscle fibres,[10] and are essential for the preservation of the integrity of the muscle cell membrane.[11]
Gamma-sarcoglycan is one of several sarcolemmal transmembrane glycoproteins that interact with dystrophin, probably to provide a link between the membrane associated cytoskeleton and the extracellular matrix. Defects in the protein can lead to early onset autosomal recessive muscular dystrophy, in particular limb-girdle muscular dystrophy, type 2C (LGMD2C).[6]
Sarcoglycanopathies are autosomal recessive limb girdle muscular dystrophies (LGMDs) caused by mutations in any of the four sarcoglycan genes: α (LGMD2D), β (LGMD2E), γ (LGMD2C) and δ (LGMD2F).[7] Severe childhood autosomal recessive muscular dystrophy (SCARMD) is a progressive muscle-wasting disorder that segregates with microsatellite markers at γ-sarcoglycan gene. Mutations in the γ-sarcoglycan gene were first described in the Maghreb countries of North Africa,[13] where γ-sarcoglycanopathy has a higher than usual incidence. One common mutation, Δ-521T, which causes a severe phenotype, occurs both in the Maghreb population and in other countries.[12] A Cys283Tyr mutation has been identified in the Gypsy population causing a severe phenotype and a Leu193Ser mutation which causes a mild phenotype.[5][14]
^ abNoguchi S, McNally EM, Ben Othmane K, Hagiwara Y, Mizuno Y, Yoshida M, Yamamoto H, Bönnemann CG, Gussoni E, Denton PH, Kyriakides T, Middleton L, Hentati F, Ben Hamida M, Nonaka I, Vance JM, Kunkel LM, Ozawa E (Nov 1995). "Mutations in the dystrophin-associated protein gamma-sarcoglycan in chromosome 13 muscular dystrophy". Science. 270 (5237): 819–22. Bibcode:1995Sci...270..819N. doi:10.1126/science.270.5237.819. PMID7481775. S2CID84713401.
^ abNowak KJ, Walsh P, Jacob RL, Johnsen RD, Peverall J, McNally EM, Wilton SD, Kakulas BA, Laing NG (Feb 2000). "Severe gamma-sarcoglycanopathy caused by a novel missense mutation and a large deletion". Neuromuscular Disorders. 10 (2): 100–7. doi:10.1016/s0960-8966(99)00063-2. PMID10714584. S2CID54410727.
^van der Kooi AJ, de Visser M, van Meegen M, Ginjaar HB, van Essen AJ, Jennekens FG, Jongen PJ, Leschot NJ, Bolhuis PA (Jun 1998). "A novel gamma-sarcoglycan mutation causing childhood onset, slowly progressive limb girdle muscular dystrophy". Neuromuscular Disorders. 8 (5): 305–8. doi:10.1016/s0960-8966(98)00040-6. PMID9673983. S2CID33437157.
^Guyon JR, Kudryashova E, Potts A, Dalkilic I, Brosius MA, Thompson TG, Beckmann JS, Kunkel LM, Spencer MJ (October 2003). "Calpain 3 cleaves filamin C and regulates its ability to interact with gamma- and delta-sarcoglycans". Muscle Nerve. 28 (4): 472–83. doi:10.1002/mus.10465. PMID14506720. S2CID86353802.
Noguchi S, McNally EM, Ben Othmane K, Hagiwara Y, Mizuno Y, Yoshida M, Yamamoto H, Bönnemann CG, Gussoni E, Denton PH, Kyriakides T, Middleton L, Hentati F, Ben Hamida M, Nonaka I, Vance JM, Kunkel LM, Ozawa E (1995). "Mutations in the dystrophin-associated protein gamma-sarcoglycan in chromosome 13 muscular dystrophy". Science. 270 (5237): 819–22. Bibcode:1995Sci...270..819N. doi:10.1126/science.270.5237.819. PMID7481775. S2CID84713401.
Vermeer S, Verrips A, Willemsen MA, ter Laak HJ, Ginjaar IB, Hamel BC (2004). "Novel mutations in three patients with LGMD2C with phenotypic differences". Pediatr. Neurol. 30 (4): 291–4. doi:10.1016/j.pediatrneurol.2003.11.006. PMID15087111.
