Objective: To analyze genetic mutations and explore its molecular pathogenesis for an hereditary protein C (PC) deficiency pedigree.
Methods: The pedigree has included 15 individuals from 4 generations. Plasma levels of PC activity (PC:A), PC antigen (PC:Ag) and other coagulant parameters were determined for members of the family. The 9 exons and intron-exon boundaries of protein C gene (PROC) of the proband were amplified with PCR and analyzed with direct sequencing. Detected mutations were confirmed with reverse sequencing. Corresponding PCR fragments from the family members were also directly sequenced.
Results: Plasma PC:A and PC:Ag for the proband was 26% and 18.60%, respectively, both being lower than normal references. Seven members from the pedigree also had lower PC:A, six had lower PC:Ag. A compound heterozygous missense mutation, including a T to G transition at position 6128 of exon 7, which results in Phe139Val, and a G to C transition at position 8478 in exon 9, which results in Asp255His, were identified in the proband. The paternal grandma, father and two aunts were heterozygous for g.6128 T to G, whilst the mother, the second uncle, sister and son were heterozygous for g.8478 G to C. There were lower PC:A in family members with g.8478 G to C.
Conclusion: The proband had inherited two independent mutations of the PROC gene including g.6128 T to G in exon 7 and g.8478 G to C in exon 9 from her father and mother, respectively. The resulting compound heterozygous mutation has caused a serious hereditary protein C deficiency.