title: Compound heterozygosity of novel missense mutations in the gamma-glutamyl-carboxylase gene causes hereditary combined vitamin K-dependent coagulation factor deficiency.
abstract: Hereditary combined vitamin K-dependent (VKD) coagulation factor deficiency is an autosomal recessive bleeding disorder associated with defects in either the gamma-carboxylase, which carboxylates VKD proteins to render them active, or the vitamin K epoxide reductase (VKORC1), which supplies the reduced vitamin K cofactor required for carboxylation. Such deficiencies are rare, and we report the fourth case resulting from mutations in the carboxylase gene, identified in a Tunisian girl who exhibited impaired function in hemostatic VKD factors that was not restored by vitamin K administration. Sequence analysis of the proposita did not identify any mutations in the VKORC1 gene but, remarkably, revealed 3 heterozygous mutations in the carboxylase gene that caused the substitutions Asp31Asn, Trp157Arg, and Thr591Lys. None of these mutations have previously been reported. Family analysis showed that Asp31Asn and Thr591Lys were coallelic and maternally transmitted while Trp157Arg was transmitted by the father, and a genomic screen of 100 healthy individuals ruled out frequent polymorphisms. Mutational analysis indicated wild-type activity for the Asp31Asn carboxylase. In contrast, the respective Trp157Arg and Thr591Lys activities were 8% and 0% that of wild-type carboxylase, and their compound heterozygosity can therefore account for functional VKD factor deficiency. The implications for carboxylase mechanism are discussed.
authors.affiliation: Laboratory of Hemostasis and Thrombosis, U689 INSERM, Hôpital Lariboisière, 41 boulevard de la Chapelle, 75475 Paris Cedex 10, France.
authors.forename: Dhouha
authors.initials: D
authors.lastname: Darghouth
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Hallgren
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Shtofman
authors.forename: Amel
authors.initials: A
authors.lastname: Mrad
authors.forename: Youssef
authors.initials: Y
authors.lastname: Gharbi
authors.forename: Ahmed
authors.initials: A
authors.lastname: Maherzi
authors.forename: Radhia
authors.initials: R
authors.lastname: Kastally
authors.forename: Sophie
authors.initials: S
authors.lastname: LeRicousse
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Berkner
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Rosa
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D025861:Blood Coagulation Disorders, Inherited / Q000201:enzymology / Q000235:genetics; D019735:Carbon-Carbon Ligases / Q000172:deficiency* / Q000235:genetics*; D002648:Child; D020147:Coagulation Protein Disorders / Q000201:enzymology* / Q000235:genetics*; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D006579:Heterozygote; D006801:Humans; D007223:Infant; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014812:Vitamin K / Q000378:metabolism*; D064417:Vitamin K Epoxide Reductases
chemical_list: D017931:DNA Primers; D014812:Vitamin K; D006899:Mixed Function Oxygenases; C578523:VKORC1 protein, human; D064417:Vitamin K Epoxide Reductases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase