Novel TCAP Mutation c.32C>A Causing Limb Girdle Muscular Dystrophy 2G

TCAP encoded telethonin is a 19 kDa protein, which plays an important role in anchoring titin in Z disc of the sarcomere, and is known to cause LGMD2G, a rare muscle disorder characterised by proximal and distal lower limb weakness, calf hypertrophy and loss of ambulation. A total of 300 individuals with ARLGMD were recruited for this study. Among these we identified 8 clinically well characterised LGMD2G cases from 7 unrelated Dravidian families. Clinical examination revealed predominantly proximo -distal form of weakness, scapular winging, muscle atrophy, calf hypertrophy and foot drop, immunoblot showed either complete absence or severe reduction of telethonin. Genetic analysis revealed a novel nonsense homozygous mutation c. 32C. A, p.(Ser11*) in three patients of a consanguineous family and an 8 bp homozygous duplication c. 26_ 33dupAGGTGTCG, p.(Arg12fs31*) in another patient. Both mutations possibly lead to truncated protein or nonsense mediated decay. We could not find any functionally significant TCAP mutation in the remaining 6 samples, except for two other polymorphisms, c. 453A. C, p.(=) and c.-178G. T, which were found in cases and controls. This is the first report from India to demonstrate TCAP association with LGMD2G.