Phenotypic and genotypic analysis of a pedigree affected with hereditary protein C deficiency due to heterozygous deletional mutation of PROC gene / 中华医学遗传学杂志

ABSTRACT

OBJECTIVE@#To analyze the phenotype and genetic variants of a pedigree affected with hereditary protein C (PC) deficiency.@*METHODS@#The protein C activity (PCA) of the proband and her family members (a four-generation pedigree including 11 individuals) were tested by chromogenic substrate method, and the protein C antigen (PCAg) was detected with an enzyme-linked immunosorbent assay(ELISA). The 9 exons and flanking sequences of the protein C (PROC) gene were amplified by PCR and directly sequenced. Suspected mutation was validated by clone sequencing and in other members of the family. MutationTaster and ClustalX-2.1-win was used to analyze the pathogenicity and conservation of the mutation site,respectively. Three-dimentional protein model and amino acids interaction were analyzed with Swiss-PdbViewer software.@*RESULTS@#The PC A and PC Ag of the proband were decreased to 46% (reference range 70%-130%) and 50% (referencerange70%-140%), respectively. Her grandmother,aunt, cousin and younger brother also showed declined PCA and PCAg by approximately 50%. Genetic analysis revealed that the above individuals have all carried a deletional mutation c.1212-1212delG (p.Met364TrpfsX15) in exon 9 of the PROC gene which can cause replacement of Methionine at position 364 by Tryptophan and alteration of 15 downstream amino acids, and produce a premature stop codon at position 378. The score of MutationTaster was 1.000, indicating that the variant is pathogenic. Conservative analysis showed that the 15 altered amino acids are located in a conserved region across nine homologous species. Protein model analysis showed that the mutation has disrupted a catalytic domain of protein C thereby affected its function.@*CONCLUSION@#The heterozygous c.1212-1212delG deletional mutation in exon 9 of the PROC gene, which was unreported previously,probably accounts for the decrease of PCA and PCAg in this pedigree.