Analysis of c.3499+200TA(7_56) and D7S523 microsatelliteslinked to Cystic Fibrosis Transmembrane Regulator

Cystic fibrosis (CF) is a life-limiting autosomal recessive disorder affecting principally respiratory and digestive
system. It is caused by cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation. The aim of
this study was to determine the extent of repeat numbers and the degree of heterozygosity for
c.3499+200TA(7_56) and D7S523 located in intron 17b and 1 cM proximal to the CFTR gene respectively. Both
microsatellites were analyzed by direct electrophoresis of PCR product on 20% polyacrylamide gel in 40 Normal
subjects and 40 CF patients originating from North Iran. 9 different alleles were found for D7S523 ranging from
16 to 24 repeats alleles. (CA)20 was the most prevalent allele both in normal individuals and CF patients with
21.3% and 20% frequencies respectively. Heterozygosity frequency of D7S523 in normal individuals and CF
patients was 97.5% and 90% respectively. Eighteen different alleles were found for c.3499+200TA(7_56)
ranging from 8 to 38 repeats alleles. (TA)9 was the most prevalent allele both in normal individuals and CF
patients with 30% and 23.5% frequencies respectively. All normal subjects and 97.5% of CF patients showed
heterozyous genotype. The high heterozygosity of the two studied microsatellites witnesses the dynamism of
such markers. High degree of heterozygosity of c.3499+200TA(7_56) and D7S523 make these markers, a very
useful tool for prenatal diagnosis especially in Iranian population.