1/13. Factor XII Tenri, a novel cross-reacting material negative factor xii deficiency, occurs through a proteasome-mediated degradation.A homozygous cross-reacting material negative factor XII-deficient patient with 3% antigen and activity levels of factor XII was screened for the identification of a mutation at the genomic level. Low-ionic strength single-stranded conformation polymorphism (SSCP) analysis and sequence analysis showed that the proband's gene for factor XII had an A-->G substitution at nucleotide position 7832 in exon 3, resulting in a Tyr34 to Cys substitution in the NH2-terminal type II domain of factor XII. We designated this mutation as factor XII Tenri. Mutagenic polymerase chain reaction (PCR), followed by KpnI digestion, showed a homozygous mutation in the proband's gene and heterozygous mutations in his parents and sister. immunoprecipitation and Western blot analyses of plasma samples from the factor XII Tenri family indicated that the proband had a trace amount of variant factor XII with an apparent molecular mass of 115 kD, which was converted to the normal 80-kD form after reduction, suggesting that factor XII Tenri was secreted as a disulfide-linked heterodimer with a approximately 35-kD protein, which we identified as alpha1-microglobulin by immunoblotting. pulse-chase experiments using baby hamster kidney (BHK) cells showed that Tenri-type factor XII was extensively degraded intracellularly, but the addition of cystine resulted in increased secretion of the mutant. Using membrane-permeable inhibitors, we observed that the degradation occurred in the pre-Golgi, nonlysosomal compartment and a proteasome appeared to play a major role in this process. On the basis of these in vitro results, we speculate that the majority of the factor XII Tenri is degraded intracellularly through a quality control mechanism in the endoplasmic reticulum (ER), and a small amount of factor XII Tenri that formed a disulfide-linked heterodimer with alpha1-microglobulin is secreted into the blood stream.- - - - - - - - - - ranking = 1keywords = antigen (Clic here for more details about this article) |
2/13. Molecular characterization of coagulation factor xii deficiency in a Japanese family.We report the identification in a Japanese family of a novel homozygous W486C mutation in the protease domain of coagulation factor XII (FXII), which was associated with the reduction of plasma FXII activity and antigen level to less than 5% of normal. Sequences of each exon for FXII gene was analysed in family members by polymerase chain reaction (PCR) amplification followed by a direct sequencing method. sequence analysis showed a homozygous substitution of G to C at nucleotide position 10587 (cDNA position 1458) in proband's FXII gene, resulting in a Trp to Cys substitution in the catalytic domain of FXII. PCR-fragment length polymorphism analysis of 55 healthy volunteers showed no such mutation. Transient expression of FXII in HK-293T cells and analysis of FXII antigen in culture media and cell lysates showed reduced secretion of mutant protein by more than 84% relative to that of wild type protein although the intracellular contents were similar. Our results suggest that the reduced secretion of FXII protein was due to incorrect folding caused by the introduction of Cys486. We designated this mutation as FXII Mie-1.- - - - - - - - - - ranking = 2keywords = antigen (Clic here for more details about this article) |
3/13. Genetic analyses and expression studies identified a novel mutation (W486C) as a molecular basis of congenital coagulation factor xii deficiency.We analyzed the factor XII (FXII) gene of a patient with congenital FXII deficiency and identified a novel amino acid substitution (W486C) in the catalytic domain. The proband was an asymptomatic 49-year-old Japanese female with abnormal coagulation test, discovered by chance. The FXII activity and antigen level were both under 10%, suggesting a cross-reacting material-negative FXII deficiency. sequence analysis of the proband's FXII gene revealed a homozygous nucleotide substitution G --> C in exon 12, resulting in the amino acid substitution W486C in the catalytic domain. We constructed the mutant FXII cDNA in an expression plasmid vector and transfected it into Chinese hamster ovary cells. The recombinant wild-type FXII antigen was detected in the culture medium by immunoprecipitation assay, but the mutant FXII (W486C) was not observed. On the other hand, both the wild-type FXII and W486C cell lysates contained FXII antigen and FXII mRNA, as estimated by western blotting and quantitative reverse transcriptase-polymerase chain reaction. These findings suggest that the W486C substitution of FXII impairs intracellular processing of the protein and/or transport system.- - - - - - - - - - ranking = 3keywords = antigen (Clic here for more details about this article) |
4/13. Characterization of factor XII Tenri, a rare CRM-negative factor xii deficiency.Factor XII Tenri (Y34C), a rare cross-reacting material (CRM)-negative factor xii deficiency, was identified in a 71-yr-old Japanese woman with angina pectoris. In the patient's plasma, factor XII activity and antigen levels were only 1.6% and 5.0%, respectively, of those seen in a normal subject. Immunoblot analysis showed that the secreted factor XII Tenri existed not only as a monomer (76 kDa), but also in complexes with apparent molecular weights of approximately 115, 140, 190, 215, and 225 kDa. After reduction with 2-mercaptoethanol, the factor XII Tenri contained in the complexes was completely converted to monomeric form on immunoblot patterns. It appeared that some of the secreted factor XII Tenri formed several types of disulfide-linked complexes, including a factor XII-alpha1-microglobulin complex, through a newly generated Cys residue. The monomeric form of factor XII Tenri, like normal factor XII, was degraded into 2 major fragments with molecular weights of approximately 45 kDa and 30 kDa following mixing with activated partial-thromboplastin-time measuring reagent (cephalin and ellagic acid), whereas the factor XII Tenri that formed the complexes was not. This indicates that the factor XII Tenri present in disulfide-linked complexes with other proteins (and itself) is not converted to active forms, suggesting that attached proteins obstruct or delay the activation of factor XII via an inhibition of its binding to a negatively charged surface in vitro.- - - - - - - - - - ranking = 1keywords = antigen (Clic here for more details about this article) |
5/13. Functional characterization of an abnormal factor XII molecule (F XII Bern).An 18-year-old healthy woman was found to have cross-reacting material (CRM)-positive factor XII (F XII) deficiency, F XII clotting activity was less than 0.01 U/mL, whereas F XII antigen was 0.11 U/mL. An F XII inhibitor was excluded. To partially characterize the molecular defect of the abnormal F XII, immunologic and functional studies were performed on the proposita's plasma. The abnormal F XII was a single chain molecule with the same molecular weight (80 Kd) and the same isoelectric points (pl, 5.9 to 6.8) as normal F XII. dextran sulfate activation of the proposita's plasma showed no proteolytic cleavage of F XII even after 120 minutes, whereas F XII in pooled normal plasma, diluted 1:10 with CRM-negative F XII-deficient plasma, was completely cleaved after 40 minutes. adsorption to kaolin was identical for both abnormal and normal F XII. In the presence of dextran sulfate and exogenous plasma kallikrein, the abnormal F XII was cleaved with the same rate as normal F XII. However, kallikrein-cleaved abnormal F XII was not able to cleave factor XI and plasma prekallikrein, in contrast to activated normal F XII. Thus, these studies show that the functional defect of this abnormal F XII, denoted as F XII Bern, is due to the lack of protease activity of the kallikrein-cleaved molecule. Therefore, the structural defect is likely to be located in the light chain region of F XII, containing the enzymatic active site.- - - - - - - - - - ranking = 1keywords = antigen (Clic here for more details about this article) |
6/13. Evaluation of the clotting defect in a factor XII-deficient kindred.A family with factor XII severe congenital deficiency is described. Factor XII activity and factor XII antigen were both undetectable in the propositus plasma; levels of FXII:C and FXII:Ag were intermediate in heterozygotes. Plasma prekallikrein activity was low in the propositus, whereas normal levels of antigen could be found, suggesting a defect of kallikrein activation due to factor xii deficiency.- - - - - - - - - - ranking = 2keywords = antigen (Clic here for more details about this article) |
7/13. Factor XII and other hemostatic protein abnormalities in nephrotic syndrome patients.Factor XII clotting activities and antigen levels were assayed in 14 plasma samples from 10 patients with nephrotic syndrome; the group was heterogeneous clinically and histologically. Factor XII was low at initial sampling in 7 of the 10 patients; in 7 of the 14 samples, factor XII antigen was in excess over clotting activity. Inhibition of factor XII could not be demonstrated; excess plasma antigen and urinary antigen (when present) had normal patterns on crossed-immunoelectrophoresis, indicating no major changes in charge or size. In 3 patients tested more than once, plasma levels of factor XII were increased up to 6fold in steroid-induced remission. Of other hemostatic factors assessed for comparison, factor viii was elevated in 11 of the 14 samples; eight of these had elevated factor VII levels as well. Eight samples from six patients showed low antithrombin iii levels; one of these patients had recurrent thromboses. antithrombin iii levels correlated with the serum albumin concentration. Only two of the eight urines tested had detectable factor XII antigen; a third had factor IX and prothrombin and no factor XII. plasminogen and antithrombin iii were readily demonstrated in all urine samples with higher concentrations in those patients with less selective proteinuria. Urinary and plasma levels were not correlated, suggesting that increased consumption or turnover was not simply related to increased filtration.- - - - - - - - - - ranking = 5keywords = antigen (Clic here for more details about this article) |
8/13. Severe Fletcher factor (plasma prekallikrein) deficiency with partial deficiency of Hageman factor (factor XII): report of a case with observation on in vivo and in vitro leukocyte chemotaxis.A case of cross-reacting material-negative Fletcher trait with additional partial deficiency of Hageman factor (HF, Factor XII) is described. Although the patient presented with a recent history of frequent epistaxis, he had no other personal or family history of a tendency toward bleeding or infection. Similar to other cases of Fletcher trait, his plasma showed a markedly prolonged partial thromboplastin time which could be corrected by prolonged incubation with the surface-activator kaolin. Surface-induced fibrinolysis, amidolysis of alpha-N-benzoyl-proline-L-phenylalanine-L-arginine-p-nitroanilide, and cold-promoted enhancement of factor VII activity, reactions requiring the presence in the plasma of fletcher factor (prekallikrein), in addition to Hageman factor and Fitzgerald factor (high-molecular weight kininogen), were also defective. In vivo chemotaxis of polymorphonuclear leukocytes and monocytes (Rebuck's skin window technique) in response to skin abrasions was defective, but was normal when diphtheria-tetanus toxoid was also applied. in vitro leukocyte chemotaxis (Boyden chamber technique) in response to normal or patient's own serum activated with zymosan was normal. Together with previous observations that kallikrein generated chemotactic activity, possibly via activation of C5, the present observations suggest that prekallikrein activation may be important for in vivo leukocyte chemotactic response to skin abrasion. The inheritance of Fletcher trait in this patient is unclear.l Although the father was an apparent heterozygote, the mother was completely normal for Fletcher factor procoagulant activity and antigen. The mild Hageman factor deficiency in the patient did not contribute significantly to the plasma defects described and was likely inherited from the father who had a low HF procoagulant activity.- - - - - - - - - - ranking = 1keywords = antigen (Clic here for more details about this article) |
9/13. hemophilia a in a phenotypic female with normal male karyotype associated with a low factor XII level.hemophilia a was detected in a 40-year-old black Gabonese female prior to thoracic surgery for empyema. The diagnosis of mild hemophilia a was supported by the findings of low factor viii coagulant activity (VIII:C 4%), normal levels of factors VIII related antigen (VIIIR:Ag) and VIII von Willebrand (VIIIR:WF), without detectable circulating anticoagulant. Neither the patient nor her immediate relatives had past histories of abnormal bleeding. The physical features were phenotypically female with developed breasts, pubic hair and normal external genitalia: however, she had primary amenorrhea, a blind vagina with no uterus and her karyotype was 46,XY. These findings are consistent with the diagnosis of testicular feminization thereby explaining the apparent contradiction between the phenotype and the known six-linked inheritance of hemophilia a. In addition to factor viii deficiency a low level of factor XII (20%) was detected although it cannot be concluded whether the patient is truly factor XII deficient or whether she represents a low variant of the normal distribution.- - - - - - - - - - ranking = 1keywords = antigen (Clic here for more details about this article) |
10/13. Classic gout in Hageman factor (Factor XII) deficiency.A 62-year-old man with a typical history of gout was admitted to the hospital with left-sided hemiplegia. His serum uric acid level was 10.3 mg/dL, his partial thromboplastin time was 198 s, and his Hageman factor (factor XII) coagulant activity and antigen were less than 1% of normal. Aspiration of synovial fluid from his inflamed knee disclosed urate crystals and abundant leukocytes but an absence of Hageman factor antigen. The presence of acute gouty arthritis in a patient with Hageman trait challenges the role of Hageman factor in the pathogenesis of gouty arthropathy.- - - - - - - - - - ranking = 2keywords = antigen (Clic here for more details about this article) |
| | Next -> |