Normal Protein C Research Articles

Term Infant with Bilateral Parenchymal Brain Hemorrhages.

Term Infant with Bilateral Parenchymal Brain Hemorrhages.

Application of Thrombomodulin-Thrombin Generation to Diverse Abnormalities of the Protein C System

Background: Increased thrombin generation is an interesting candidate as a potential indicator of hypercoagulability and thrombosis risk. Increased thrombin generation using the calibrated automated thrombogram (CAT) has been reported in antithrombin deficiency but the CAT does not reflect protein C deficiency without the addition of thrombomodulin (TM). TM activates protein C (PC) in the CAT and reduces thrombin generation. Objective: The objective of this study was to determine the capacity of the TM-augmented CAT to detect defects in various protein C system components; the lupus anticoagulant was also investigated as a cause of decreased protein C activation. Methods: The CAT-TM was performed with reagents and methods per the manufacturer's instructions using 5 pM tissue factor and TM (Stago). Other assays included: PC (chromogenic), free protein S (PS, LIA), activated protein C resistance (aPTT-based clotting assay), factor V Leiden (FVL PCR) and lupus anticoagulant (LA, dRVVT and Staclot LA, Stago). Platelet poor plasma samples were obtained from the biobank of a consented prospective inceptional cohort study of thrombosis and thrombophilia or a positive family history of either (ThromboPICS #05-0339); samples from healthy controls with no personal or family history of thrombosis or thrombophilia were collected on a consented protocol (#09-0816). Samples from participants on therapeutic inhibitors of factor Xa or thrombin were treated with appropriate neutralizers; no sample was tested on warfarin. Clinical data included gender, age (< 18 versus ≥ 18 years), history of thrombosis, timing of sample from most recent thrombosis (acute < 14 days; subacute 14-90 days; or chronic > 90 days) and use of anticoagulants at the time of the blood draw. Tests for violations of normality were negative. Therefore, results of cohorts versus controls were compared with independent sample t-test and subgroup analyses relative to control used One-Way ANOVA. Post-hoc comparisons of each subgroup to the controls were collected for multiple comparisons using the Bonferroni correction. Results: Ninety-nine cases and 45 normal controls were studied. Overall half of the cases had a history of thrombosis and 66% of those with thrombosis were on no anticoagulation at the time of testing. Table 1 displays results of the CAT-TM in the 2 control and 6 study groups. Control adults and children showed a mean 50% thrombin reduction in thrombin generation with CAT-TM; overall, persons with protein C system defects showed approximately 25% reduction, with the least reduction of thrombin generation in the cohort of PC deficiency at 19%. Sensitivity of the CAT-TM was 100% for PC deficiency, 81% for LA positivity, 80% for PS deficiency and 72% for FVL positivity with no difference in degree of thrombin reduction between hetero- and homozygous FVL. In addition, we identified 14 individuals with CAT-TM results similar to protein C system defects but with confirmed normal PC, PS, FVL and LA tests. Although 9 of these unknowns had a personal (7) or family (2) history of thrombosis, five came from the healthy controls. The false positive results in 3 adult and 2 pediatric controls conferred a CAT-TM test specificity of 89%. Furthermore, analyses showed no differences in CAT-TM results related to gender, age group, history of thrombosis, age of clot at blood draw (acute, subacute or chronic) or use of anticoagulation at the time of blood draw. Conclusions: The CAT-TM is a useful screening test for defects in the protein C system, including LA, although this test could not discriminate between heterozygous and homozygous FVL. The etiology of positive CAT-TM in normal individuals or individuals with a personal or family history of thrombosis without identified PC system defects is currently unknown and under ongoing investigation. Disclosures No relevant conflicts of interest to declare.

Peculiar laboratory phenotype/ genotype relationship due to compound inherited protein C defects in a child with severe venous thromboembolism

A 7-years-old child who developed unprovoked deep vein thrombosis (DVT) and pulmonary embolism (PE) was tested for inherited thrombophilia. Protein C (PC) antigen level (87 %) and PC coagulometric and amidolytic activities (12 % and 11 %, respectively) were consistent with a homozygous PC type IIA phenotype.The patient was carrier of two heterozygous missense mutations causing p.Arg32Cys substitution associated with a type I PC defect ("null allele", from the paternal side) and p.Gly433Ser substitution responsible for a type IIA PC defect (from the maternal side). Thus, the apparently normal PC antigen level in the proband was misleading in the interpretation of phenotype/genotype relationship of this compound PC defect. The child was also carrier of heterozygous prothrombin G20210A variant.Severe venous thromboembolism can occur in otherwise healthy children with complex inherited thrombophilia. Careful laboratory characterization of the phenotype/genotype relationship can be crucial to correctly classify PC defects and for their management with anticoagulants or replacement therapy.

Phenotypic detection and structure analysis of a PC missense mutation (Met406Ile) resulted in venous thromboembolism

To identify the phenotypic detection and structure analysis of a protein C (PC) missense mutation (Met406Ile) resulting in venous thromboembolism. Pedigree research was performed for a hereditary PC deficiency pedigree. Chromogenic assay was used for phenotypic diagnosis to detect the AT activity. All 9 exons were amplified by polymerase chain reaction (PCR) and direct sequencing analysis was performed for PCR products. The corresponding mutation sites of family members were detected.Homology modeling was used for reconstructing mutant PC construction. The effects of construction change were analyzed. The PC activities of proband and 4 family members decreased to different extents by 29.7%, 42.2%, 42.4%, 67.3% and 70.7% respectively. Among them, the proband and other three family members carried the same mutation (c.1218G > A, Met406Ile) while another family member had a PC polymorphism (rs1799810). Homology modeling showed that VDW's interaction radius of amino acids decreased after mutation (Met406Ile).In particular, the radius of Gly418:C and Ile406CG2, Gly418:C and Ile406HG23, Leu419:N and Ile406:HG23 decreased to 2.0733å, 1.620 45å and 1.446 52å respectively. Compared with normal PC, the interaction energy of mutant PC rose from -8.504 54 to 1210.04 kal/mol. And the change of VDW interaction energy was significant. The mechanism of this pedigree is caused by PROC gene missense mutation on exon 9 (c.1218G > A, Met406Ile). The regional amino acids of mutant PC collide with each other and lead to an instability of PC reconstruction.

Genetic variants associated with protein C levels

Normal protein C (PC) plasma levels range widely in the general population. Factors influencing normal PC levels are thought to influence the risk of venous thrombosis. Little is known about the underlying genetic variants. We performed a genome scan of normal PC levels to identify genes that regulate normal PC levels. We performed a variance components linkage analysis for normal PC levels in 275 individuals from a single, large family. We then sequenced candidate genes under the identified linkage peak in eight family members: four with high and four with low, but normal, PC levels. For variants showing a difference in carriers between those with high and low PC levels, we re-evaluated linkage in the 275 family members conditional on the measured genotype effect. Genotype-specific mean PC levels were determined using likelihood analysis. Findings were replicated in the Leiden Thrombophilia Study (LETS). We identified a quantitative trait locus at chromosome 5q14.1 affecting normal PC plasma level variability. Next-generation sequencing of 113 candidate genes under the linkage peak revealed four SNPs in BHMT2, ACOT12, SSBP2 and XRCC4, which significantly increased PC levels in our thrombophilic family, but not in LETS. We identified four genes at chromosome 5q14.1 that might influence normal PC levels. BHMT2 seems the most likely candidate to regulate PC levels via homocysteine, a competitive inhibitor to thrombin. Failure to replicate our findings in LETS might be due to differences between the studies in genetic background and linkage disequilibrium patterns.

Safety of plasma‐derived protein C for treating disseminated intravascular coagulation in adult patients with active cancer

Cancer-related disseminated intravascular coagulation (DIC) is a life-threatening condition for which no effective treatment is currently available. Protein C (PC), a modulator of coagulation as well as the inflammatory system, has been successfully tested (in its activated recombinant form [a-rPC]) in sepsis-related coagulopathy, but with an increased risk for major bleeding. Plasma-derived PC (pd-PC) is more suitable than a-rPC in patients at high risk from bleeding due to its self-limiting process. We carried out a single-arm study evaluating the role of pd-PC in adult cancer patients with overt DIC. Over a period of 3 years, we treated 19 patients with overt DIC and a PC plasma concentration <50%; all received PC concentrate (Ceprotin(®), Baxter) for 72 hr in adjusted doses to restore normal PC values (70-120%). Blood coagulation, haematological tests, and the DIC score were recorded after 12, 24, 48 hr, 7 and 10 days, while clinical outcomes (bleeding, thrombosis and mortality) were recorded up to 28 days. Within 48 hr of starting pd-PC therapy, laboratory tests as well as the DIC score improved in all patients. At 28-days follow-up, no bleeding or thrombosis was observed. This is the first study to investigate the use of pd- PC for treatment of cancer-related overt DIC.

Normal levels of protein C and protein S tested in the acute phase of a venous thromboembolic event are not falsely elevated

BackgroundProtein C (PC) and protein S (PS) determination is part of the thrombophilia investigation in patients with idiopathic venous thromboembolism (VTE). Based on scarce evidence it is a common notion that PC and PS levels decrease during the acute phase of VTE, necessitating delay of testing and temporary transition from warfarin to low molecular weight heparin. We have previously demonstrated that an abnormal PC or PS result determined within 24 hours of VTE diagnosis and before the initiation of warfarin needs to be repeated for confirmation ≥3 months after starting treatment and ≥14 days after stopping anticoagulation therapy. In the current study, we sought to show that normal PC and PS values determined during the acute phase of VTE are not false negatives.Methods99 patients with acute idiopathic VTE who had normal PC and PS determination within the first 24 hours of presentation and who subsequently had their oral anticoagulation discontinued after six months of therapy. PC and PS determinations were repeated ≥6 months after starting treatment and ≥ 14 days after stopping warfarin. Proportions of patients who tested abnormal on the second test were calculated and 95% confidence intervals obtained using the Wilson's score method. Data from a previously published study on patients with abnormal initial tests was included for comparison.ResultsNone of the 99 patients who had normal PC and PS initially had an abnormal result on repeated testing (0%; 95% CI 0 - 3.7%). Data from the previous study showed that, among patients who initially had abnormal results, 40% (95%CI 35.4-84.8%) were confirmed to have low PC and 63.6% (95%CI 16.8-68.7%) low PS on repeated testing. The difference between proportions was statistically significant (χ2 p-value < 0.001).ConclusionOur results suggest that PC and PS can be determined during the acute phase of VTE and whereas abnormal results need to be confirmed with repeat testing at a later date, a normal result effectively rules out deficiency with only one test.

High Levels of Protein C Are Determinated by PROCR H3 in a Dutch Family.

Abstract 2139Poster Board II-116The natural anticoagulant protein C (PC) circulates in blood at a concentration of about 60 nM. Inter-individual variations in the levels of PC are in part genetically determined, but which loci in the genome are involved is only partially known. In a recent study we identified a locus on chromosome 20 which was associated with high PC levels in a large pedigree from the GENES study (LOD score >5 at 55 cMorgan). Candidate genes related to the PC pathway under the LOD-1 region encoded FOXA2 (previously known as HNF3 beta, a nuclear factor regulating protein C gene transcription), thrombomodulin (THBD,which is key to activation of PC), and the endothelial protein C receptor (PROCR). Here we present data that pinpoint a SNP in PROCRas being responsible for the observed segregation of high PC levels. The pedigree has 218 members and was ascertained through a proband with a family history of venous thrombosis (VT). Classical genetic risk factors for thrombosis (i.e. PC-, PS-, antithrombin deficiency, factor V Leiden and prothrombin G20201A) were not present. Complete medical data, plasma measurements and DNA was available for 161 family members. The mean age was 47±15 (range 15-87) years. The mean PC plasma level was 116±25% (range 72-212). Four family members had experienced VT and 2 had had recurrence. These symptomatic members had normal to high PC levels (66, 82, 114 and 178%).Haplotypes (and genotypes) for PROCR were determined in the family members by TaqMan assay using tag SNPs (single nucleotide polymorphisms) and PROCR H3 was associated with the levels of PC in the family. Furthermore, the promoter, exons, and 3`UTR of the 3 candidate genes were sequenced in 13 individuals, 9 with high and 4 with normal plasma PC levels. Critical SNPs that were encountered during sequencing were genotyped in all family members, namely FOXA2 rs1055080 (3`UTR) and rs2277764 (promoter region). As those 2 SNPs were inherited together in the set of 13 patients and also in the LETS (data not shown), our further analysis used only rs1055080. Plasma soluble endothelial protein C receptor (sEPCR) and soluble thrombomodulin (sTM) levels were measured with an ELISA assay. PC and sEPCR and levels were compared between PROCR H3 and FOXA2 rs1055080 carriers and non carriers by Student's t-test. sTM was analyzed by Mann-Whitney test. Association between PC levels and sEPCR/sTM levels were evaluated using linear regression analysis. Afterwards associations were adjusted for the PROCR H3 and FOXA2 rs1055080 SNP separately to detect their possible confounding effect. DNA sequencing only yielded previously reported SNPs in FOXA2, THBD and PROCR. Only the above mentioned SNPs were associated with PC plasma levels. Linkage analysis for PC levels using the original markers (from Marshifield) and adding the new PROCR and FOXA2 SNPs did not change the LOD score. When the analysis was adjusted for the mentioned markers, the LOD score dropped below 2. sEPCR has a bimodal distribution; mean ± SD was 103±27 ng/ml for the first mode and 262±70 ng/ml for the second mode. Median (range) sTM was 1.2 ng/ml (0.1-4). Linkage analysis for sEPCR levels yielded a high LOD score (above 6) that was accentuated to above 8 when PROCR H3 was included as a marker. For sTM, the LOD score was low with every combination of markers. PC, sEPCR and sTM levels were compared between PROCR H3 carriers and non-carriers and both PC levels and sEPCR levels were influenced by this PROCR haplotype, but not sTM. In conclusion, chromosome 20 harbors a locus which influences PC levels and also the levels of sEPCR, but not the levels of sTM. A detailed analysis with SNPs in PROCR, THBD and FOXA2suggests that the so-called PROCR H3 is directly responsible for the increased PC and sEPCR levels in this family. PROCR H3 is known to represent a g.A6936G substitution leading to a p.Ser219Gly replacement in the transmembrane domain of EPCR. The Gly219 isoform is more sensitive to sheddases (such as the ADAM17 metalloprotease) and is associated with generation of truncated mRNA lacking the transmembrane domain. However, the exact mechanism by which EPCR and sEPCR levels influence the level of PC remains to be determined Disclosures:No relevant conflicts of interest to declare.

Mice with a severe deficiency in protein C display prothrombotic and proinflammatory phenotypes and compromised maternal reproductive capabilities.

Anticoagulant protein C (PC) is important not only for maintenance of normal hemostasis, but also for regulating the host immune response during inflammation. Because mice with a designed total genetic deficiency in PC (PC-/- mice) die soon after birth, attempts to dissect PC function in various coagulation/inflammation-based pathologies through use of mice with less than 50% of normal PC levels have not been successful to date. In the current investigation, we have used a novel transgenic strategy to generate different mouse models expressing 1-18% of normal PC levels. In contrast to PC-/- mice, mice with only partial PC deficiency survived beyond birth and also developed thrombosis and inflammation. The onset and severity of these phenotypes vary significantly and are strongly dependent on plasma PC levels. Our findings additionally provide the first evidence that maternal PC is vital for sustaining pregnancy beyond 7.5 days postcoitum, likely by regulating the balance of coagulation and inflammation during trophoblast invasion. These low PC-expressing transgenic mouse lines provide novel animal models that can be used to elucidate the importance of PC in maintenance of the organism and in disease.

The prevalence of protein C, protein S, and antithrombin III deficiency in non-APS/SLE Chinese adults with noncardiac cerebral ischemia.

Protein C (PC), protein S (PS), and antithrombin III (AT-III) are vital thrombin antagonists in circulation. However, the prevalence of these natural inhibitors for cerebral ischemia is barely mentioned in the Chinese population. The prevalence of PC, PS, and AT-III deficiency in Chinese adults with cerebral ischemia is reported. The study subjects were free of antiphospholipid antibody syndrome or systemic lupus erythematosus. Cardiac, liver, and renal function were normal. An overall rate of thrombophilia was 27%. PS deficiency was the most common disorder, followed by PC with PS and PC deficiency. There was only one patient with AT-III deficiency. No gender was specific for thrombophilia. However, PS deficiency was predilected in young adults. A positive correlation between PC and AT-III was achieved in patients with a normal PC activity but not PC deficiency. There was no correlation between AT-III or PS. The odds ratios of PC and PS were 5.29 and 2.86, respectively. Accordingly, an inability for thrombin antagonization by the PC/PS axis may relate to the occurrence of cerebral ischemia in the Chinese population. AT-III seems to display a minor role only.

Abnormal Propeptide Processing Resulting in the Presence of Two Abnormal Species of Protein C in Plasma

A heterozygous G-->T transversion at position 1388 of the protein C (PC) gene which predicted the substitution of Arg(-1) to a Leu (PC(R-1L)) was identified in a thrombophilic patient. The PC(R-1L) was purified from the patient's plasma by immunoaffinity chromatography using Ca++-independent and Ca++-dependent monoclonal antibodies. NH2-terminal sequencing of the light chain of PC(R-1L) revealed two amino acid sequences: one was identical to the complete propeptide sequence of PC, while the other matched the normal PC light chain sequence elongated by one amino acid (Leucine at position 1). Activated PC(R-1L/propeptide) exhibited normal amidolytic and impaired anticoagulant activity. Thus, the substitution of a Leu for an Arg at position -1 of PC shifts the propeptidase cleavage site by one amino acid. In addition, in PC(R-1L/propeptide) the propeptide cleavage at Lys(-2) is less efficient since approximately 60% of PC variant molecules present in patient's plasma retained the entire propeptide. Our findings suggest that depending on the specific amino acid substitution at position-1, PC can be secreted in plasma containing the entire propeptide attached to the light chain. Impaired interaction of elongated APC molecules with a membrane-surface and/or factor Va which is the physiological substrate for APC, is manifested in vivo by thrombophilia.

Venous Thromboembolism Associated With Double Heterozygosity for R506Q Mutation of Factor V and for T298M Mutation of Protein C in a Large Family of a Previously Described Homozygous Protein C-Deficient Newborn With Massive Thrombosis

It is remarkable that certain patients with heterozygous protein C (PC) deficiency manifest venous thromboembolism (VTE), whereas others, particularly those belonging to families with homozygous PC deficiency, remain asymptomatic. The goals of the present study of a family, in which the proband had homozygous PC deficiency, were to identify members with and without VTE, to determine the mutation causing PC deficiency, and to search for the R506Q mutation of factor V (FV) causing activated PC resistance. Heterozygosity for a T298M mutation in exon 9 of the PC gene was found in the father of the homozygous proband who died of massive thrombosis. Based on analysis of a three-dimensional molecular model of PC, we speculate that this mutation causes type I deficiency due to disruption of packing of hydrophobic side chains and loss of an H-bond between Q184 and T298. Forty-six family members were examined for the T298M mutation by polymerase chain reaction (PCR) amplification of exon 9 and restriction analysis using Mae III and for the FV R506Q mutation by PCR amplification of exon 10 and restriction analysis using Mnl I. VTE was observed in five of 11 members who were heterozygous for both PC and FV mutations. In contrast, VTE was not observed for the PC mutation in 13 heterozygotes who had normal FV, including the parents of the deceased proband, 10 heterozygotes for the FV mutation who had normal PC, and 12 individuals bearing neither mutation. These observations extend recent evidence of an increased thrombotic risk conferred by the coexistence of heterozygous PC deficiency and heterozygous activated PC resistance and support the paradigm in which hereditary thrombophilia is often a multigenic disease.

Venous thromboembolism associated with double heterozygosity for R506Q mutation of factor V and for T298M mutation of protein C in a large family of a previously described homozygous protein C-deficient newborn with massive thrombosis

It is remarkable that certain patients with heterozygous protein C (PC) deficiency manifest venous thromboembolism (VTE), whereas others, particularly those belonging to families with homozygous PC deficiency, remain asymptomatic. The goals of the present study of a family, in which the proband had homozygous PC deficiency, were to identify members with and without VTE, to determine the mutation causing PC deficiency, and to search for the R506Q mutation of factor V (FV) causing activated PC resistance. Heterozygosity for a T298M mutation in exon 9 of the PC gene was found in the father of the homozygous proband who died of massive thrombosis. Based on analysis of a three- dimensional molecular model of PC, we speculate that this mutation causes type I deficiency due to disruption of packing of hydrophobic side chains and loss of an H-bond between Q184 and T298. Forty-six family members were examined for the T298M mutation by polymerase chain reaction (PCR) amplification of exon 9 and restriction analysis using Mae III and for the FV R506Q mutation by PCR amplification of exon 10 and restriction analysis using Mnl I. VTE was observed in five of 11 members who were heterozygous for both PC and FV mutations. In contrast, VTE was not observed for the PC mutation in 13 heterozygotes who had normal FV, including the parents of the deceased proband, 10 heterozygotes for the FV mutation who had normal PC, and 12 individuals bearing neither mutation. These observations extend recent evidence of an increased thrombotic risk conferred by the coexistence of heterozygous PC deficiency and heterozygous activated PC resistance and support the paradigm in which hereditary thrombophilia is often a multigenic disease.

Gene Analysis of an Abnormal Protein C with a Mutation of GAG for Glu26 to AAG for Lys

We report a missense mutation of protein C (PC) gene in a family with type II congenital. PC deficiency. The proband was a 17-year-old high school student with deep venous thrombosis and pulmonary embolism. Hemostatic examinations revealed normal amidolytic activity and PC antigen level measured by a chromogenic snake venom assay and an EIA utilizing a polyclonal antibody, respectively. However, anticoagulant activity measured by the activated partial thromboplastin time method and immunological antigen level estimated by a monoclonal antibody recognizing the Ca2+-dependent conformational change were reduced. Two other members. of this family (father and paternal grand-mother) showed the identical defect, but they had been asymptomatic. The functional abnormalities were most likely to be due to alternation in the Gla domain. Subsequently, a polymerase chain reaction (PCR) strategy and an allele-specific oligonucleotide (ASO) hybridization were used to evaluate exon 3 of the PC gene. Sequence analysis following amplification of exon 3 and its flanking regions showed a single G to A transition, resulting in the conversion of Glu26 codon (GAG) to Lys26 codon (AAG). Since this missense mutation generated no new restriction site, the PCR-amplified exon 3 fragments from this family member were hybridized with ASOs corresponding to the normal and mutated sequences. An identical mutation was detected in the affected family members of the proband by the ASO hybridization. These data indicate that conversion of the Glu26 codon (GAG) to Lys26 codon (AAG) was responsible for the type II congenital PC deficiency inherited in this Japanese family.

The Gla26 Residue of Protein C Is Required for the Binding of Protein C to Thrombomodulin and Endothelial Cell Protein C Receptor, but not to Protein S and Factor Va

A functionally defective protein C (PC)-Mie, detected the plasma of a patient with hereditary thrombophilia, has Lys substituted for gamma-carboxyglutamic acid (Gla)26 residue. The activation rate of PC-Mie by Protac or thrombin in the absence of Ca2+ and that by thrombin with native thrombomodulin (TM), recombinant soluble truncated TM or on cultured endothelial cells in the presence of Ca2+ were all apparently lower than that of normal PC. The anticoagulant activity of Protac-activated PC (APC)-Mie on the plasma clotting time and the rate of inactivation of factor Va by APC-Mie in the presence of phospholipids were lower than those seen with normal APC. APC-Mie and normal APC bound equally to protein S and to biotinyl-factor Va. However, neither PC-Mie nor APC-Mie bound to phospholipids and to cultured human endothelial cells. It was similar to that observed with Gladomainless PC/APC, but different from that seen with normal PC/APC. These results suggest that Gla26-dependent conformation is required for the binding of PC/APC to phospholipids, TM and the surface of endothelial cell PC/APC receptor, but not to protein S and factor Va.

Ectopic Transcript Analysis Indicates that Allelic Exclusion is an Important Cause of Type I Protein C Deficiency in Patients with Nonsense and Frameshift Mutations in the PROC Gene

Nonsense mutations, deletions and splice site mutations are a common cause of type I protein C deficiency. Either directly or indirectly by altering the reading frame, these lesions generate or may generate premature stop codons and could therefore be expected to result in premature termination of translation. In this study, the possibility that such mutations could instead exert their pathological effects at an earlier stage in the expression pathway, through "allelic exclusion" at the RNA level, was investigated. Protein C (PROC) mRNA was analysed in seven Spanish type I protein C deficient patients heterozygous for two nonsense mutations, a 7bp deletion, a 2bp insertion and three splice site mutations. Ectopic RNA transcripts from patient and control lymphocytes were analysed by RT-PCR and direct sequencing of amplified PROC cDNA fragments. The nonsense mutations and the deletion were absent from the cDNAs indicating that only mRNA derived from the normal allele had been expressed. Similarly for the splice site mutations, only normal PROC cDNAs were obtained. In one case, exclusion of the mutated allele could be confirmed by polymorphism analysis. In contrast to these six mutations, the 2 bp insertion was not associated with loss of mRNA from the mutated allele. In this case, cDNA analysis revealed the absence of 19 bases from the PROC mRNA consistent with the generation and utilization of a cryptic splice site 3' to the site of mutation, which would result in a frameshift and a premature stop codon. It is concluded that allelic exclusion is a common causative mechanism in those cases of type I protein C deficiency which result from mutations that introduce premature stop codons.

A novel dysfunctional protein C (Protein C Padua 2) associated with a thrombotic tendency: substitution of Cys for Arg‐1 results in a strongly reduced affinity for binding of Ca++

A dysfunctional protein C (PC) molecule (Protein C Padua 2) was found in a 40-year-old man presenting with recurrent deep vein thrombosis/pulmonary embolism and a family history of thrombotic disease. The patient exhibited a normal PC antigen level, normal chromogenic activity (using Protac as PC activator) but markedly reduced coagulometric activity. After adsorption of patient plasma onto Al(OH)3, between 30% and 45% PC antigen/chromogenic activity but no coagulometric activity was detectable in the supernatant. The dysfunctional molecule exhibited reduced affinity for a Ca++ dependent anti-protein C monoclonal antibody as detected by specific ELISA assay. Immunoblotting experiments showed that PC Padua 2 had an increased MW (95 kD v 65 kD for normal PC). The lesion responsible was determined by PCR/direct sequencing to be a heterozygous CGT/TGT transition in exon 3 of the protein C gene resulting in the substitution of Arg by Cys at residue--1 in the pro-peptide leader sequence. The presence of a high MW PC was consistent with the fact that (part of) the propeptide (at least Cys-1) still was attached to the protein C molecule. This finding could also explain the strongly reduced affinity of PC Padua 2 for the Ca++ dependent anti-protein C monoclonals.

Protein C Activity in Healthy Volunteers - Influence of Age, Sex, Smoking and Oral Contraceptives

Interpretation of protein C (PC) levels in a given individual has several limitations. A normal PC activity does not necessarily exclude a genetic deficiency nor can a reduced level confirm it. Measuring PC amidolytic activity in 9,648 healthy blood donors has allowed identification of demographic factors which cause variation in PC activity and further hinder interpretation. PC activity displays a log normal distribution and significant variation with age. This is most marked in young adult males when mean PC activity rises from 0.86 iu/ml (15-19 years) to 1.04 iu/ml (45-49 years; P < 0.0001). Pre-menopausal females, who for most age ranges, have mean PC activity below their male contemporaries, show a less marked rise with age until the menopause when PC activity rises further. The use of hormonal contraceptive preparations is associated with an increase in mean PC activity of 0.05-0.08 iu/ml while smoking habit has no influence on PC activity. In view of these findings we strongly recommend the use of age and sex restricted reference ranges when interpreting PC activity.

Isolation and Characterization of a Mouse Protein C cDNA

Protein C (PC) is a vitamin K-dependent serine protease, a deficiency of which results in thrombus. There is no spontaneously occurring mouse model of the disease. Attempts to create such a model in mice by using anti-sense gene technology requires isolation of a normal mouse PC cDNA. When a mouse liver (BALB/c) cDNA library was screened using a human PC cDNA as a probe, nine overlapping cDNA clones were isolated and sequenced. The cloned mouse PC cDNA comprised 1,512 nucleotides and the open reading frame of the cDNA encoded a polypeptide of 461 amino acids residues including a leader peptide composed of 41 amino acids. Mouse PC exhibited high homology to both human and bovine PCs. Mouse PC also had several structural features common in other PCs; locations of 23 Cys residues, location of putative beta-hydroxy Asp71, possible carbohydrate attachment sites involving Asp residues at amino acid positions 249, 314, and 330, and location of active sites such as His212, Asp258, and Ser361. Northern blot hybridization analysis identified a single species of mouse PC mRNA (2.0 kb in length) in mouse liver.

蛇毒を用いたプロテインＣ活性の測定 先天性プロテインＣ欠乏症，播種性血管内凝固症候群，血栓性血小板減少性紫斑病，糖尿病，肝障害およびワーファリン服用患者におけるプロテインＣ抗原との比較

Functional protein C (PC) activity (both anticoagulant and amidolytic) was measured using a specific PC activator extracted from the venom of Agkistrodon contortrix in 4 patients with hereditary PC deficiency, 37 with disseminated intravascular coagulation (DIC), 9 with thrombotic thrombocytopenic purpura (TTP), 8 with diabetes mellitus (DM), 8 with liver injury and 30 under long-term warfarin therapy. The results were compared with those obtained by an immunological assay (ELISA). In patients with hereditary PC deficiency, DIC and TTP, PC activity was closely related with PC antigen levels. Both functional and immunological PC were decreased in many patients with DIC, while most TTP patients had normal PC levels. Some DM patients had high PC antigen levels, and their PC activity was somewhat lower than the antigen levels. PC activity and antigen were decreased in patients with hepatic injury, but in some of them functional assays (especially anticoagulant assay) gave lower PC values than the immunoassay. During stabilized warfarin treatment, PC antigen and amidolytic activity were decreased in parallel, but a decrease in anticoagulant activity was more pronounced. In addition, only anticoagulant activity correlated significantly with thrombotest values.These results indicate that the measurement of PC activity is valuable for the assessment of the behavior of PC in various disease states. Only anticoagulat PC assay can evaluate the PC function in patients under oral anticoagulant therapy and in some patients with hepatic injury.