in point mutation-negative hereditary protein S deWciency

Abstract Hereditary protein S (PS) deWciency is an auto-somal disorder caused by mutations in the PS gene (PROS1). Conventional PCR-based mutation detection identiWes PROS1 point mutations in approximately 50 % of the cases. To verify if gross copy number variations (CNVs) are often present in point mutation-negative here-ditary PS deWciency we used multiplex ligation-dependent probe ampliWcation (MLPA) as a detection tool in samples from individuals with a high probability of having true PS deWciency. To this end, DNA samples from nine PS deW-cient probands with family members (seven type I and two type III) and nine isolated probands (three type I and six type III), in whom PROS1 mutations were not found by DNA sequencing, were evaluated. An independent quanti-tative PCR (qPCR) was performed to conWrm the Wndings of the MLPA assay. Family members were also tested when DNA was available. Gross abnormalities of PROS1 were found in six out of eighteen probands. In three pro-bands complete deletion of the gene was detected. Two probands had a partial deletion involving diVerent parts of the gene (one from exon 4 through 9 and another from exon 9 through 11). One family showed a duplication of part of PROS1. qPCR analysis was in accordance with these results. In conclusion, this study substantiates that gross gene abnormalities in PROS1 are relatively common in hereditary PS deWcient patients and that MLPA is a useful tool for direct screening of CNVs in PROS1 point muta-tion-negative individuals