Direct molecular analysis of FMR-1 gene mutation in patients with fragile Xq syndrome and their families

Background: The unequivocal diagnosis of fragile Xq syndrome is based in th e direct analysis of the underlying FMR-1 gene mutation, that consists in a n increased number of trinucleotide CGG repetitions. Aim: To study families with fragile Xq syndrome, using the Southern technique for the analysis of the mutation. Subjects and methods: Fifteen individuals, pertaining to 6 f amilies with fragile Xq syndrome, were done. Results: Five male individuals had a clinically evident syndrome, confirmed by cytogenetic analysis that showed fragility in 10 to 29% of studied cells. One subject with a clinical picture suggesting fragile Xq had a normal cytogenic study. The other stud ied subjects were the mothers of the five subjects with the syndrome, that must be carriers, and four brothers. Molecular analysis showed that seven s ubjects (5 males) had a complete mutation, five (4 females) were carriers o f a pre mutation and three (2 males) did not have the mutation. Conclusions : The Southern technique allows to verify the normal condition of FRAXA loc us, identify carriers and to detect complete mutations in fragile Xq syndro me.