Gross deletions/duplications in PROS1 are relatively common in point mutation-negative hereditary protein S deficiency

Abstract

Hereditary protein S (PS) deficiency is an autosomal disorder caused by mutations in the PS gene (PROS1). Conventional PCR-based mutation detection identifies PROS1 point mutations in approximately 50% of the cases. To verify if gross copy number variations (CNVs) are often present in point mutation-negative hereditary PS deficiency we used multiplex ligation-dependent probe amplification (MLPA) as a detection tool in samples from individuals with a high probability of having true PS deficiency. To this end, DNA samples from nine PS deficient 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 quantitative PCR (qPCR) was performed to confirm the findings 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 probands complete deletion of the gene was detected. Two probands had a partial deletion involving different 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 deficient patients and that MLPA is a useful tool for direct screening of CNVs in PROS1 point mutation-negative individuals.

Molecular basis of protein S deficiency in China

“…Using quantitative PCR, Johansson et al [46] found large deletions in 3 out of 8 ProS-deficient families (37.5%) who were PROS1 gene mutation-negative. Pintao et al [35] identified gross abnormalities in 6 out of 18 probands (33.3%) who were mutation-negative and suggested that MLPA is a useful tool to uncover gross mutations. Furthermore, LindHalld en et al [47] detected large deletions in 5 out of 8 families (62.5%) that were previously sequenced and identified no mutations.…”

“…In addition, multiplex ligationdependent probe amplification (MLPA) was employed to detect large or gross variations of the PROS1 gene in cases in which no mutation was detected by direct sequencing, but repeatedly low ProS activity suggested a genetically determined deficiency. For this analysis, the SALSA MLPA P112 PROS1 kit (MRC-Holland, Amsterdam, Netherlands) was used [35]. It contains 15 probes for 12 of the 15 exons, one probe for the promoter region and one probe for the potential exon 4 of the ProS pseudogene.…”

Inherited Thrombophilia: Past, Present, and Future Research

“…Type I PS deficiency is most frequently observed and often a consequence of missense mutations in the protein S gene (PROS1). Copy number variations were found in 33% of a group of missense negative patients with PS deficiency (Pintao et al, 2009). These copy number variations included deletion of the whole PROS1 gene, partial gene deletions and partial duplications.…”

Protein C and protein S deficiencies: similarities and differences between two brothers playing in the same game

“…In the PROSIT study, mutations in PROS1 were found only in 70% of probands with PS deficiency (17). However, using DNA sequencing methods, large deletions or gene segment duplications may remain undetected (74,75). Moreover, there are mutations affecting the transcription regulatory sequences at the 5' of the gene (76,77).…”