Hereditary Protein C Deficiency Associated with Mutations in Exon IX of the Protein C Gene

Abstract

SummaryThis report describes five families with symptomatic hereditary protein C deficiency. Using a polymerase chain reaction (PCR)-based method, the entire coding sequence and intron-exon boundaries of the protein C gene was amplified from genomic DNA. In each family a single point mutation in the protein C gene was identified. Two unrelated families were found to share the same mutation, while the other three had different mutations. In the first two families with type I protein C deficiency the normal cytosine residue at nucleotide position 8551 in the protein C gene was replaced by thymidine leading to substitution of the normal proline residue at amino acid position 279 by leucine. In the third family with type I deficiency a previously undescribed mutation was identified. In this family the guanosine residue at position 8559 was replaced by adenosine (glycine 282 substituted by serine). In the fourth family, also with type I deficiency, guanosine 8589 was replaced by adenosine (glycine 292 substituted by serine). The fifth family had type II deficiency and in affected members cytosine 8769 was replaced by thymidine (arginine 352 substituted by tryptophan). All these mutations lead to amino acid substitutions in the serine protease domain of the mature protein. All were able to be confirmed by restriction enzyme analysis of PCR-derived DNA. In addition the novel mutation at nucleotide position 8559 was also demonstrable using single strand conformation polymorphism (SSCP) analysis of PCR-derived DNA. These mutations were likely examples of deamination of methylated cytosine occurring in cytosine-phosphate-guanosine (CpG) dinucleotide sequences. These findings confirm the genetic heterogeneity of hereditary protein C deficiency in these families.

Defective Sorting to Secretory Vesicles in Trans-Golgi Network Is Partly Responsible for Protein C Deficiency

“…These genetic abnormalities were the same mutations reported previously, 13,17,21 but PC R352W and PC G376D had not been observed previously in the Japanese population. PC R169W has a molecular defect in the activation process by the thrombin/thrombomodulin complex, 21 and PC plasma levels are decreased, although the abnormal molecules are present in the circulation.…”

“…PC R169W has a molecular defect in the activation process by the thrombin/thrombomodulin complex, 21 and PC plasma levels are decreased, although the abnormal molecules are present in the circulation. Patients with mutants PC R352W and PC G376D reportedly develop a type I PC deficiency, 13,17 but the molecular basis for the impaired secretion of these abnormal molecules has not been reported.…”

“…In the human PC, Asp71 is modified to a ␤-hydroxylated residue and is thought to be involved in high-affinity calcium ion binding. 10 Many clinical reports have shown that patients with decreased circulating levels of PC develop thrombophilia, [11][12][13][14][15] with venous thrombosis in heterozygotes and purpura fulminans in homozygotes. A wide variety of genetic mutations can lead to PC deficiency and PC molecular abnormality.…”

“…A wide variety of genetic mutations can lead to PC deficiency and PC molecular abnormality. [11][12][13][14][15] We found genetic mutations in three patients with thrombotic episodes and decreased levels of plasma PC. In the present study, we expressed wild-type PC and PC mutants corresponding to the respective genetic abnormalities of each patient to elucidate the molecular mechanisms of the secretion of wild-type PC and impaired secretion of abnormal PC.…”

Protein C and protein S deficiencies: similarities and differences between two brothers playing in the same game

“…Missense mutations are the most frequently reported types; the resulting amino acid change involving the Gla-domain or the pro-peptide result in defective calcium and phospholipid binding (49)(50)(51)(52)(53)(54)(55)(56)(57). Mutations in the serine protease domain result in defective protease activity or decreased substrate binding (58)(59)(60).…”