A missense mutation in gamma-glutamyl carboxylase gene causes combined deficiency of all vitamin K-dependent blood coagulation factors

To identify potential mutations in the gamma-glutamyl carboxylase gene, the sequence of all exons and intron/exon borders was determined in 4 patients from a consanguineous kindred with combined deficiency of all vitamin K-de pendent procoagulants and anticoagulants and results were compared with nor mal genomic sequence. Ail 4 patients were homozygous for a point mutation i n exon 9 that resulted in the conversion of an arginine codon (CTG) to leuc ine codon (CGG) at residue 394. Screening of this mutation based on introdu ction of Alu I site in amplified fragment from normal allele but not from t he mutated allele showed that 13 asymptomatic members of the kindred were h eterozygous for the mutation. The mutation was not found in 340 unrelated n ormal chromosomes, The segregation pattern of the mutation which is the fir st reported in the gamma-glutamyl carboxylase gene fits perfectly with phen otype of the disorder and confirms the suggested autosomal recessive patter n of inheritance of combined deficiency of all vitamin K-dependent procoagu lants and anticoagulants in this kindred. The mutated carboxylase protein e xpressed in Drosophila cells was stable but demonstrated threefold reduced activity compared with WT carboxylase, confirming that the L394R mutation r esults in a defective carboxylase, (C) 1998 by The American Society of Hema tology.