Private ?- and ?-sarcoglycan gene mutations: Evidence of a founder effect in Northern Italy

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Abstract
Autosomal recessive muscular dystrophies called “sarcoglycanopathies” result from mutations in the genes encoding α‐, β‐, γ‐, or δ‐sarcoglycan complex components. The present study involved six unrelated families from Northern Italy showing mutations in the β‐ or γ‐sarcoglycan genes. An 8 bp duplication in the β‐sarcoglycan gene and 1 bp insertion in the γ‐sarcoglycan gene occur with high frequency in our population. These mutations have never been reported thus far in other countries. Many patients are homozygotes for a single mutation, although they derived from non‐consanguineous marriages. We suggest that these alleles are “private” mutations of this geographical region. A panel of highly informative microsatellite markers that map in the β‐ and γ‐sarcoglycan gene locus was used to assess the haplotypes among affected patients and control population, in order to test the presence of linkage disequilibrium. We found that the 8 bp duplication in the β‐sarcoglycan gene and the 1 bp insertion in the γ‐sarcoglycan gene are in linkage disequilibrium with neighbouring polymorphisms. The recurrence of specific sarcoglycan mutations in Northern Italy is probably due to a founder effect, combined with a relative genetic isolation. Hum Mutat 16:13–17, 2000.