IDENTIFICATION OF 19 PROTEIN-S GENE-MUTATIONS IN PATIENTS WITH PHENOTYPIC PROTEIN-S DEFICIENCY AND THROMBOSIS

Protein S is a protein C-dependent and independent inhibitor of the co agulation cascade. Deficiency of protein S is an established risk fact or for venous thromboembolism. We have used a strategy of specific amp lification of the coding regions and intron/exon boundaries of the act ive protein S gene (PROS1) and direct single-strand solid phase sequen cing, to seek mutations in 35 individuals with phenotypic protein S de ficiency. Nineteen point mutations (16 novel) in 19 probands (or relat ives of probands) with venous thromboembolism are reported here. Fifte en of the 19 mutations were expected to be causal and included 10 miss ense mutations (Lys9Glu, Glu26Ala, Gly54Glu, Cys145Tyr. Cys200Ser, Ser 283Pro, Gly340Asp. Cys408Ser, Ser460Pro, and Cys625Arg). Three of the 15 mutations resulted in premature stop codons (delete T 635 producing a stop codon at position 126, Lys368stop and Tyr595stop) and two were at intron/exon boundaries (+1 G to A in intron d and +3 A to C in int ron j). Of the remaining four mutations, three were within intronic se quence and one was a silent mutation within the coding region and did not alter amino acid composition. In two of the 10 missense mutations, reduced plasma protein S activity compared with antigen level suggest ed the presence of variant (type II) protein S. (C) 1996 by The Americ an Society of Hematology.