Optimization of a simple and rapid single-strand conformation analysis for detection of mutations in the PROS1 gene: Identification of seven novel mutations and three novel, apparently neutral, variants

Anticoagulant protein S (PS) deficiency is a known risk factor for thrombophilia. The structure and high allelic heterogeneity of the PS gene (PROS1), together with the presence of a 97% homologous pseudogene, complicates PROS1 analysis. We have optimized a simple, fast, and non-isotopic Single-Strand Conformation Analysis (SSCA or SSCP) method for PROS1 mutation detection. This is accomplished through the analysis of the single-stranded and heteroduplex DNA fragments corresponding to 15 PCR segments that include part of the 5'-upstream region and the 15 PROS1 exons with their intron boundaries. To standardize the method, 13 known PROS1 mutations or allele variants in 10 different fragments were analyzed under different electrophoretic conditions. The results indicated that, using a combination of two different electrophoretic settings, all the allele variants could be detected as a single-strand band shift and/or by the presence of a heteroduplex. This method was used to analyze the PROS1 gene in 31 propositi with different types of PS deficiency and thrombosis. Ten different cosegregating mutations, seven of which are novel (143C-G, L-27H, G96X, M599T, P626L, 1418delA, and 1877delT), were identified in the five families suffering from type I or quantitative PS deficiency and in four of the nine families with coexistence of type I and type III phenotypes. No clearly co-segregating PROS1 mutations were identified in any of the 17 type III propositi analyzed, although eight of them were heterozygotes for the uncommon P460 allele of the S/P460 variant. Furthermore, five apparently neutral allelic variants, three of which are novel (-296C-T, 182G-C and T57S), were identified in a normal control, two type I/III and two type III PS-deficient pedigrees.