Identification of a shared, common haplotype segregating with an SGCB c.544T>G mutation in Indian patients affected with sarcoglycanopathy

Abstract

Abstract Sarcoglycanopathy is the most frequent form of autosomal recessive limb-girdle muscular dystrophies caused by mutations in SGCB gene encoding beta-sarcoglycan proteins. In this study, we describe a shared, common haplotype co-segregating in 14 sarcoglycanopathy cases from 13 unrelated families from south Indian region with the likely pathogenic homozygous mutation c.544T>G (p.Thr182Pro) in SGCB. Haplotype was reconstructed based on 5 polymorphic markers surrounding the c.544T>G mutation in the cases and related family members as well as 150 unrelated controls from general Indian populations using PLINK1.9. We identified haplotype H1= G, A, T, G, G, T at a significantly higher frequency in cases compared to related controls and general Indian population. Upon segregation analysis within the family pedigrees, H1 is observed to co-segregate with c.544T>G in a homozygous state in all the pedigrees of cases except one indicating a probable event of founder effect. Furthermore, Identical-by-descent and inbreeding coefficient analysis revealed relatedness among 33 new pairs of seemingly unrelated individuals from sarcoglycanopathy cohort and a higher proportion of homozygous markers, thereby indicating towards common ancestry. Since all these patients are from the south Indian region, we suggest this region to be a primary target of mutation screening in patients diagnosed with sarcoglycanopathy.