IDENTIFICATION OF 2 DIFFERENT MUTATIONS CAUSING PROTEIN-S DEFICIENCY IN 2 UNRELATED BELGIAN FAMILIES USING A NONISOTOPIC SCANNING AND SEQUENCING METHOD

Hereditary protein S deficiency is a risk factor for developing recurr ent venous thromboembolic disease and is caused by a defect in the pro tein S 1 (PROS I) gene. Identification of the mutation in the PROS 1 g ene can overcome diagnostic uncertainty in family members with borderl ine protein S levels. We describe a novel nonisotopic method for molec ular diagnosis of protein S deficiency, using fluorescein-labeled ampl ification and sequencing primers. As a first step, all exons of the PR OS1 gene are selectively amplified, and heteroduplex analysis is perfo rmed. As a second step, all exons are analyzed by direct sequencing. U sing this method, we have characterized the molecular defect in two Be lgian families with hereditary protein S deficiency type I: a frameshi ft mutation in exon XIV (1881insTC) and a missense mutation caused by a T-to-C transition, resulting in substitution of Leu405 by Pro (L405P ).