Severe gamma-sarcoglycanopathy caused by a novel missense mutation and a large deletion

We report two siblings with a relatively severe limb-girdle muscular dystro phy. The elder sister presented at 8 years of age with inability to climb a nd abnormal gait. At 12 years she was barely ambulant. Pier sister followed a similar course. Serum creatine kinase was 8500-10 000 IU (N 25-200) in t he elder sister and 17 000-19 000 IU in the younger sister. Muscle biopsy o f the elder sister at 8 years showed chronic myopathic changes with loss of muscle fibres, active necrosis and regeneration. Immunocytochemistry demon strated normal spectrin and dystrophin, reduced alpha-sarcoglycan and absen t gamma-sarcoglycan - indicating a gamma-sarcoglycanopathy. Haplotype analy sis for the markers D13S115, DI3S232, D13S292, D13S787, DI3S1243 and D13S28 3 internal to and flanking the gamma-sarcoglycan gene showed the affected s isters shared haplotypes, indicating it was possible they were suffering fr om a gamma-sarcoglycanopathy. Non-inheritance of paternal alleles for D13S2 32, D13S292 and DI3S1243 suggested the inheritance of a deletion, which was confirmed by FISH, using a genomic probe from the gamma-sarcoglycan gene. The gamma-sarcoglycan cDNA was amplified by reverse transcriptase PCR from the muscle biopsy of the elder sister and sequenced. A missense mutation ch anging codon 69 from GGC glycine to CGC arginine was identified. HhaI diges tion of exon 3 genomic PCR products showed the two affected sisters were he mizygous for the mutation, while the mother and grandmother were heterozygo tes. The mutation, identified by SSCP analysis, was not observed in 116 unr elated, unaffected individuals. previously, only two other missense mutatio ns, the Cys283Tyr missense mutation in Gypsies and the Leu193Ser mutation i n a Dutch family, have been described in the gamma-sarcoglycan gene. The fa ct that the affected individuals in the current and Gypsy families are gamm a-sarcoglycan negative may indicate that codons 69 and 283 are important in gamma-sarcoglycan function. (C) 2000 Elsevier Science B.V. All rights rese rved.