Calpainopathy (LGMD2A) in Croatia: molecular and haplotype analysis.

Aim: To determine types and frequency of CAPN3 mutations in 29 unrelated Croatian families, analyzed during 6-year prospective and ongoing genetic and epidemiological study of muscular dystrophies in Croatia.

Methods: Mutation analysis included allele-specific polymerase chain reaction (PCR) or combination of PCR and restriction fragment length polymorphisms (RFLP) methods. Haplotype analysis was performed by PCR and DNA electrophoresis using 5 highly polymorphic markers flanking CAPN3 gene locus.

Results: Mutation analysis revealed the presence of 6 different CAPN3 mutations (550delA, R541W, P82L, delFWSAL, R49H, Y537X), accounting for 94.8% of CAPN3 chromosomes in the studied population. 550delA was the most frequent mutation, found in 43/58 (74%) CAPN3 chromosomes, whereas the frequency of other five mutations ranged from 2-9%. Haplotype analysis of 38 chromosomes carrying 550delA mutation showed the presence of the same haplotype on 66% of analyzed chromosomes.

Conclusions: The present data, together with our previously published results, explain the frequency and the distribution of the 550delA mutation in Croatia by founder effect and genetic drift. Results of haplotype study are in favor of the hypothesis that 550delA is an old, rather than a recurrent mutation. The findings are important for effective diagnostic screening of CAPN3 gene in Croatia and neighboring countries, as well as for accurate genetic counseling.