Activation-resistant homozygous protein C R229W mutation causing familial perinatal intracranial hemorrhage and delayed onset of thrombosis. Issue 143 (July 2016)

• Record Type: Journal Article
• Authors: Alsultan, Abdulrahman; Gale, Andrew J.; Kurban, Kadijah; Khalifah, Mohammed; Albadr, Fahad B.; Griffin, John H.
• Is Part Of: Thrombosis research. Issue 143(2016)
• Page Start: 17
• Page End: 21
• Publication Date: 2016-07
• Subjects: Intracranial hemorrhage -- Mutation -- Neonate -- Protein C -- Thrombosis; Thrombosis -- Periodicals; 616.135
• DOI: 10.1016/j.thromres.2016.04.011
• Languages: English
• ISSNs: 0049-3848

Abstract

Abstract: Introduction: We describe a family with two first-degree cousins who presented with similar phenotypes characterized by neonatal intracranial hemorrhage and subsequent onset of thrombosis. Patients/methods: We enrolled the two affected patients, five unaffected family members and fifty-five normal controls. Clinical, laboratory, and radiological characteristics of patients were obtained. Exome sequencing was performed for the older affected child. PROC c.811 C > T was genotyped by PCR in patients, family members, and controls. Protein C amidolytic activity and antigen were measured using the STACHROM® protein C kit and ELISAs. To define functional abnormalities caused by the patients' mutation, recombinant wildtype protein C and its mutants R229W, R229Q and R229A were studied. Results: For the two cousins, protein C amidolytic activity was 61% and 59% and antigen was 57% and 73% (nl 70–140%), respectively. Exome sequencing revealed a homozygous variant in exon 9 of the protein C ( PROC ) gene c.811 C > T (R229W). The R229W mutation is located in the calcium binding loop of protein C's protease domain that mediates thrombomodulin interactions. Recombinant R229W-protein C mutant was strikingly defective in rate of activation by thrombin: thrombomodulin, suggesting an in vivo deficit in these children for generation of activated protein C. Conclusions: These cases emphasize that protein C and activated protein C are important in maintaining the integrity of the brain vascular endothelium in humans. Moreover, routine protein C assays utilizing snake venom protease fail to detect protein C mutants that are resistant to thrombin:thrombomodulin activation. Highlights: Protein C is a natural anticoagulant and its deficiency increases risk of thrombosis. Homozygous protein C gene ( PROC ) c.811 C > T mutation (R229W) was identified in one family. Protein C R229W mutation was linked to perinatal intracranial bleeding and delayed onset of thrombosis. Recombinant protein C mutant R229W is resistant to thrombin:thrombomodulin activation.