Molecular prenatal diagnosis of ataxia telangiectasia heterozygosity by direct mutational assays

Ataxia telangiectasia (AT) is a severe autosomal recessive disease, rare but not infrequent in Italy. Owing to the seriousness of the disease, prenatal diagnosis has been attempted in the past by means of cytogenetic, biochemical, radio-biological and indirect molecular analyses. We performed the first direct molecular prenatal diagnosis of AT on a chorionic villi sample from a 37-year-old woman at the 10th week of pregnancy. She had two previous children suffering AT and two induced abortions. At molecular analysis her affected children were compound heterozygotes for mutations 7792C-->T in exon 55 (from the mother) and 8283delTC in exon 59 (from the father). The prenatal diagnosis was performed by two different operators in double-blind form. Mutation 7792C-->T was studied by restriction enzyme analysis using TaqI. Mutation 8283delTC was screened by heteroduplex analysis. The fetus was heterozygous for the mutation 7792C-->T (confirmed by sequencing). In order to verify the possible contamination by maternal DNA, polymorphic loci HLA-DRB1 and HLA-DQA1, together with microsatellite markers D6S259, D11S2000, D11S29, D11S1778 and D11S2179, were examined. All these loci were informative, showing that the fetus received only one allele from each parent. The heterozygosity for ATM mutation 7792C-->T was confirmed by molecular studies after the birth of a healthy male baby.