Abdulrahman Alsultan1, Andrew J Gale2, Kadijah Kurban3, Mohammed Khalifah3, Fahad B Albadr4, John H Griffin2. 1. Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia. Electronic address: aalsultan1@ksu.edu.sa. 2. Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA. 3. Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia. 4. Department of Radiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
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.
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.
Authors: P H Reitsma; F Bernardi; R G Doig; S Gandrille; J S Greengard; H Ireland; M Krawczak; B Lind; G L Long; S R Poort Journal: Thromb Haemost Date: 1995-05 Impact factor: 5.249