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C K Kasper

Publications and source records attributed to C K Kasper.

At least 19 recordsLinked to original sources
PubMed2001

Frequency of recent retrotransposition events in the human factor IX gene.

Two germline retrotransposition mutations of recent origin were observed in 727 independent mutations (0.28%) in the human factor IX gene (F9) of patients with hemophilia B: 1) a 279 bp insertion in exon H originating from an Alu family of short interspersed elements not previously known to be active and, 2) a 463 bp insertion in exon E of a LINE1 element originating in the maternal grandmother. If the rates of recent germline mutation in F9 are typical of the genome, a retrotransposition event is estimated to occur somewhere in the genome of about one in every 17 children born. Analysis of other estimates for retrotransposition frequency and overall mutation rates suggests that the actual rate of retrotransposition is likely to be in the range of one in every 2.4 to 28 live births.

Alu Elements↗
PubMed2000

Novel hotspot detector software reveals a non-CpG hotspot of germline mutation in the factor IX gene (F9) in Latin Americans.

Two-base substitutions at each of two nucleotides in the factor IX gene (F9), but not part of CpG dinucleotides, were recently reported in a small population sample collected in Mexico, a significant observation of recurrent sites ("hotspots") of mutation (P=0.00005). When these new data were combined with previously collected mutation data into two progressively larger and inclusive Latin American samples, additional mutations were observed at one recurrent site, nucleotide 17747, and an additional recurrent nucleotide was observed such that the recurrent nucleotides in these larger samples were also significant (P=0.0003 and 0.0003). In contrast, in three non-Latin American control samples, there was at most only one nucleotide that recurred only once, most likely a chance recurrence (P>/=0.5). When the significance of substitutions was analyzed at each recurrent nucleotide individually, nucleotide 17747 was shown to be a significant recurrent nucleotide by itself in all the Latin American population samples (P</=0.02). Furthermore, a standard statistical comparison of mutation frequencies in the previously collected data alone confirmed that the frequency of mutation at nucleotide 17747 is significantly higher in Latin Americans than in all other populations combined (P=0.01). Thus, nucleotide 17747 is a germline mutation hotspot in F9 specific to Latin American populations. This may be the first evidence for population-specific effects on germline mutation that causes human genetic disease. The significance of the observed recurrent sites was analyzed using new software called Hotspot Detector which is capable of detecting significant recurrent sites in small samples, extending the sensitivity of F9 as a human germline mutagen test. Hotspot Detector uses a Monte-Carlo simulation method that was validated by comparing its results with those from an exact probability formula derived from statistical theory.

CpG Islands↗
PubMed1999

Reported in vivo splice-site mutations in the factor IX gene: severity of splicing defects and a hypothesis for predicting deleterious splice donor mutations.

Small consensus sequences have been defined for RNA splicing, but questions about splicing in humans remain unanswered. Analysis of germline mutations in the factor IX gene offers a highly advantageous system for studying the mutational process in humans. In a sample of 860 families with hemophilia B, 9% of independent mutations are likely to disrupt splicing as their primary mode of action. This includes 26 splicing mutations reported herein. When combined with the factor IX splice mutations reported by others, at least 104 independent mutations have been observed, 80 of which are single base substitutions within the splice donor and splice acceptor consensus sequences. After analysis of these mutations, the following inferences emerge: (1) the susceptibility of a splice donor sequence to deleterious mutation depends on the degree of similarity with the donor consensus sequence, suggesting a simple "5-6 hypothesis" for predicting deleterious vs. neutral mutations; (2) the great majority of mutations that disrupt the splice donor or splice acceptor sequences result in at least a 100-fold decrement in factor IX coagulant activity, indicating that the mutations at these sites generally function as an on/off switch; (3) mutations that create cryptic splice junctions or that shorten but do not interrupt the polypyrimidine tract in the splice acceptor sequence can reduce splicing by a variable amount; and (4) there are thousands of potential donor-acceptor consensus sequence combinations in the 38-kb factor IX gene region apparently not reduced by evolutionary selective pressure, presenting an apparent paradox; i.e., mutations in the donor and acceptor consensus sequences at intron/exon splice junctions can dramatically alter normal splicing, yet, appropriately spaced, good matches to the consensus sequences do not predispose to significant amounts of alternative splicing.

Computer Simulation↗
PubMed1999

Germline origins in the human F9 gene: frequent G:C-->A:T mosaicism and increased mutations with advanced maternal age.

The factor IX gene (F9) is an advantageous system for analyzing recent spontaneous germline mutation in humans. Herein, the male:female ratio of mutation ("r") in F9 have been estimated by Bayesian analysis from 59 germline origin families. The overall "r" in F9 was estimated at 3.75. The "r"s varied with the type of mutation. The "r"s ranged from 6.65 and 6.10 for transitions at CpG and A:T to G:C transitions at non-CpG dinucleotides, respectively, to 0.57 and 0.42 for microdeletions/microinsertions and large deletions (>1 kb), respectively. The "r" for the two subtypes of non-CpG transitions differed (6.10 for A:T to G:C vs 0.80 for G:C to A:T). Somatic mosaicism was detected in 11% of the 45 origin individuals for whom the causative mutation was visualized directly by genomic sequencing of leukocyte DNA (estimated sensitivity of approximately one part in 20). Four of the five defined somatic mosaics had G:C to A:T transitions at non-CpG dinucleotides, hinting that this mutation subtype may occur commonly early in embryogenesis. The age at conception was analyzed for 41 US Caucasian families in which the age of the origin parent and the year of conception for the first carrier/hemophiliac were available. No evidence for a paternal age effect was seen. However, an advanced maternal age effect was observed (P=0.03) and was particularly prominent for transversions (average of the 79th percentile when maternal age was normalized for the year of conception). This suggests that an increased maternal age results in a higher rate of transmitted mutation, whereas the increased number of mitotic replications associated with advanced paternal age has little, if any, effect on the rate of transmitted mutation.

Adolescent↗
PubMed1999

Human recombinant DNA-derived antihaemophilic factor (factor VIII) in the treatment of haemophilia A: conclusions of a 5-year study of home therapy. The KOGENATE Study Group.

Fifty-eight previously treated haemophilic subjects were treated exclusively with the recombinant FVIII (rFVIII-KOGENATE) produced by Bayer Corporation (Berkeley, CA) in an international multicentre prospective study of more than 5 years duration. Fifty-four of the 58 had severe haemophilia (< 2% FVIII) and four had moderate haemophilia (2-5% FVIII); 23/58 (40%) were seropositive for HIV, while 35/58 (60%) were HIV seronegative. Patients were monitored for safety and efficacy over a median period of 4.7 years (range 0.9-5.9 years) and received 17 922 infusions totalling 25.7 million units of rFVIII. Of 7107 bleeding episodes reported in home diaries, 5831 (82%) required only one treatment with rVIII. Twenty-five invasive surgical procedures in 17 patients, including eight joint replacements, were successfully accomplished and 13 serious bleeding episodes in eight patients were successfully treated. FVIII recovery performed on 885 occasions using 39 different lots of rFVIII showed mean incremental recovery of 2.48% IU-1 kg-1 (+/- 0.64). Adverse events were associated with 42 infusions (0.2%); none caused discontinuation of therapy. Immunological parameters remained stable in HIV-seronegative subjects treated with rFVIII; a small decrease in CD4 counts was noted in HIV-seropositive individuals (mean - 37.2 cells mm-3 yr-1). No de novo formation of inhibitors to FVIII was noted; and no clinical allergic reactions occurred to murine or hamster proteins. These conclusions from the longest monitored safety study ever performed for a haemophilia treatment product (with more than 5 years of observation) confirm previous interim study reports that rFVIII is well tolerated over the long-term, has biological activity comparable to that of plasma-derived FVIII, and is safe and efficacious for the treatment of haemophilia A.

Adolescent↗
PubMed1999

Haemophilia B Brandenberg-type promoter mutation.

We report the second confirmed case of the haemophilia B 'Brandenberg' phenotype. At the time of testing, patient HB530 was a 17-year-old post-puberty male with a persistent, clinically severe bleeding disorder and markedly reduced plasma procoagulant factor IX activity (< 1%). Sequencing studies revealed a G-->A transition at bp - 26 within the promoter region of the factor IX gene. This case report confirms the observation that not all patients with promoter mutations improve after puberty and supports the hypothesis that bp - 26 is a critical binding site within the factor IX gene promoter region for both constitutive as well as androgen-inducible transcription factors.

Adolescent↗
PubMed1999

Kinetics of factor IX activity differ from that of factor IX antigen in patients with haemophilia B receiving high-purity factor IX replacement.

Pharmacokinetic studies in haemophilia B have found in vivo recovery of FIX (FIX) to be uniformly lower than the factor VIII recovery in haemophilia A. We hypothesized that this lower recovery could result from rapid binding to high-affinity receptors on platelets and endothelium. To test this hypothesis, we evaluated the kinetics of FIX activity and protein in haemophilia B patients. Twelve patients were enrolled in a double dosing, crossover study with two high-purity FIX concentrates, AlphaNine SD and MonoNine. Subjects were given 40 U kg-1 of FIX concentrate and blood samples were taken at 15, 30, and 60 min. A second infusion of 40 U kg-1 was given after the 60 min blood sample and further blood samples removed at 15, 60, 120, and 360 min after the second dose. Patients were infused with the alternate concentrate at least 7 days later. Plasma samples were assayed for FIX activity by coagulation assay and antigen by RIA. FIX antigen in the infused concentrates was measured and quantified as microg U-1. There was no difference between the two FIX concentrates (AlphaNine vs. MonoNine) in the initial (15 min) activity (57% +/-1 19% vs. 53% +/-1 12%) and antigen (62% +/-1 16% vs. 55% +/-1 19%) recoveries. Recoveries after the second FIX dose were not statistically different than those observed after the first FIX dose. In one patient, a doubling of the initial infusion dose did not increase FIX recovery after the second FIX dose. However, the recovery of FIX antigen was significantly greater than the recovery of FIX activity and the differences became more significant in the post-15 min samples. We calculated a ratio of plasma FIX antigen to FIX activity in microg U-1. Average antigen to activity ratio increased from 5.8 +/-1 1.9 microg U-1 at 15 min to 7.1 +/-1 2.2 microg U-1 at 60 min. At 420 min the ratio increased to 9.3 +/-1 2.4 microg U-1. Although these studies failed to demonstrate a significant FIX receptor pool, they did demonstrate a phenomenon of progressive loss of biologic activity of the FIX protein after infusion of FIX concentrates.

Blood Platelets↗
PubMed1998

Germline mutations in Peruvian patients with hemophilia B: pattern of mutation in AmerIndians is similar to the putative endogenous germline pattern.

Exogenous (e.g., environmental) mutagens produce characteristic patterns of mutation. In contrast, endogenous mutation processes likely are associated with an invariant pattern of mutation. Analysis of factor IX gene mutations among large samples of hemophilia B patients from multiple, widely divergent geographic and ethnic populations reveals a remarkably constant mutational pattern, suggesting that the primary germline mutational process results from endogenous processes rather than environmental mutagens. To test this hypothesis further, we have initiated a study of hemophilia B patients from Peru because relatively large populations of AmerIndians can be found with low admixtures of other races. To determine if the factor IX (FIX) germline mutational pattern in AmerIndians differs from the common and putative endogenous pattern, FIX gene mutations were characterized in an initial sample of 10 AmerIndian Peruvian patients with hemophilia B. A minimum of 2.2 kb of the FIX gene was examined by PCR and direct sequencing of all eight exons, the splice junctions, and the promoter region. The pattern of germline mutation in AmerIndians was similar to the pattern of FIX germline mutations from larger U. S. Caucasian or Mexican Hispanic samples (P=0.55 and 0.63, respectively). The similar pattern in this initial sample of the Peru AmerIndian population provides additional support for the inference that the FIX germline mutational pattern results from predominantly endogenous processes rather than exogenous mutagens.

Factor IX↗
PubMed1998

A randomized, double-blind comparison of two dosage levels of recombinant factor VIIa in the treatment of joint, muscle and mucocutaneous haemorrhages in persons with haemophilia A and B, with and without inhibitors. rFVIIa Study Group.

Recombinant factor VIIa (rFVIIa) was developed to provide an improved procoagulant component capable of 'by-passing' inhibitor antibodies in the treatment of haemophilic patients. The primary objective of this study was to compare the efficacy of two dosage regimens of rFVIIa (given intravenously at periodic intervals) in the treatment of joint, muscle and mucocutaneous haemorrhages in persons with haemophilia A and B with and without inhibitors. The study was designed as a randomized, double-blind, parallel group, international multicenter trial. Patients were randomly allocated to treatment A: 35 mu kg-1 or B: 70 mu kg-1, in blocks of 2. Within each block, one patient was assigned to the 35 mu kg-1 dosing regimen and the other to 70 mu kg-1 dose. One hundred and fifty subjects from 20 sites were screened for this study and 116 had baseline assessments. Of these, 84 were treated on the protocol and 32 were not treated in the study, in most cases because they did not return to the clinic with an eligible bleeding episode. One hundred and seventy-nine bleeding episodes were treated, of which 145 (81%) were acute haemarthroses. Both treatments were efficacious, with 71% having an excellent (59% and 60%) or effective (12% and 11%) response. Overall, the mean and median number of doses given per episode of joint bleeding were 3.1 and 2, respectively. The mean number of doses was 3.1 for the 70 mu kg-1 group and 2.7 for the 35 mu kg-1 group (P value = 0.142). The study concluded that rFVIIa in a dosage of 35 mu kg-1 or 70 mu kg-1 is both safe and reasonably effective in the treatment of joint or muscle haemorrhages in haemophilic patients with inhibitor antibodies to factor VIII or factor IX. It is concluded that the appropriate dose for the treatment of joint and peripheral muscle bleeding in haemophilic patients with inhibitors is 35-70 mu kg-1 given at 2-3 h intervals until haemostasis is achieved.

Adult↗
PubMed1998

Factor VIII inhibitors in mild and moderate-severity haemophilia A. UK Haemophilia Centre Directors Organisation.

Twenty six patients with mild or moderate haemophilia A and inhibitors are described. The inhibitor was detected at a median age of 33 years, after a median of 5.5 bleeding episodes. This usually following intensive replacement therapy. The median presenting inhibitor titre was antihuman 11.6 BU/ml, antiporcine 1.45 BU/ml. Plasma basal factor VIII level declined from a median of 0.08 IU/ml to 0.01 IU/ml following the inhibitor development. This caused spontaneous bleeding in 22 and a bleeding pattern similar to acquired haemophilia in 17. Bleeding was often severe and caused two deaths. The inhibitor disappeared spontaneously, or following immune tolerance induction, in 16 cases after a median of 9 months (range 0.5-46), with a return to the original baseline VIIIC level and bleeding pattern accompanied inhibitor loss. The inhibitor persisted in the remainder of the cases over a median period of 99 months (range 17-433 months) of follow-up. Inhibitors are an uncommon complication of mild haemophilia which frequently persist and may be associated with severe, life-threatening, haemorrhage. Forty-one percent of treated haemophilic family members had a history of factor VIII inhibitors, suggesting a familial predisposition to develop inhibitors in these kindreds. Sixteen patients from 11 families were genotyped. Seven different missense mutations affecting the light chain were detected and two in the A2 domain. Five patients from three families had a mutation causing a substitution of Trp2229 by Cys in the C2 domain which appears to predispose to inhibitor formation since 7 of the 18 affected individuals have a history of inhibitor development.

Adolescent↗
PubMed1996

Structural integrity of the gamma-carboxyglutamic acid domain of human blood coagulation factor IXa Is required for its binding to cofactor VIIIa.

This report describes the analysis of a novel mutant human factor IX protein from a patient with hemophilia B (factor IX activity <1%; factor IX antigen 45%). Enzymatic amplification of all eight exons of the factor IX gene followed by direct sequence analysis reveals a single nucleotide change (a guanine --> adenine transition) in exon 2 at nucleotide 6409 which results in a glycine --> arginine substitution at amino acid 12 in the gamma-carboxyglutamic acid rich (Gla) domain of the mature protein. Factor IX was isolated by immunoaffinity chromatography from plasma obtained from the proband. The purified protein is indistinguishable from normal factor IX by polyacrylamide gel electrophoresis. Characterization of the variant in purified component assays reveals that it is activated normally by its physiologic activator factor XIa, but its phospholipid-dependent activation by the factor VIIa-tissue factor complex is diminished. In the presence of phospholipid and 5 mM Ca2+, the activities of variant and normal plasma-derived factor IX are similar; however, in the presence of activated factor VIIIa (intrinsic tenase complex), the normal augmentation of the cleavage of the specific substrate of factor IX, factor X, is not observed. The determination of the association constants for normal and variant factor IXa with factor VIIIa shows that the affinity of the activated variant factor IX for the cofactor factor VIIIa is 172-fold lower than normal. Competition studies using active site-inactivated factor IXas in the intrinsic tenase complex confirm that the defect in the variant protein is in its binding to factor VIIIa. We conclude that the structural integrity of the Gla domain of human factor IX is critical for the normal binding of factor IXa to factor VIIIa in the intrinsic tenase complex. In addition, a glycine at amino acid 12 is necessary for normal activation of factor IX by the factor VIIa-tissue factor complex.

Adenine↗
PubMed1996

Safety profile of porcine factor VIII and its use as hospital and home-therapy for patients with haemophilia-A and inhibitors: the results of an international survey.

A multicentre retrospective survey was conducted to re-assess the use of porcine factor VIII (HYATE:C), its side effects and the selection of patients for regular or home-therapy. 15,152,000 units of HYATE:C were used by 154 patients. The median inhibitor cross-reactivity to porcine VIIIC of 137 patients was 15%, 27% of patients lacking cross-reactivity. An absent, intermediate or brisk specific antiporcine anamnestic response was observed in 29, 40 and 31% of patients respectively. Seven patients were treated on-demand as home-therapy for a median 6.2, range 1.5-13 years, 23 further patients were treated regularly in hospital for a median of 3, range 2-7 years. This group used 8,319,000 U of porcine VIIIC for 2,000 bleeding episodes. The incidence of transfusion reactions was 0.001%, 0.64% and 2.3%, for domiciliary infusions, infusions in multiply treated in-patients, and unselected in-patient infusions, respectively. The risk of reactions was dose-related. A post-infusion fall in platelet count was common, but usually transient and clinically insignificant. This was also dose-related (r = -0.64, p = 0.002). Marked reductions in platelet count were occasionally seen, usually with intensive replacement therapy. The relative lack of side effects observed amongst patients treated at home is attributable to the low, median 33 U/kg, dose used by this group. A subgroup of inhibitor patients, identifiable by their absent or modest anamnestic response to porcine factor VIII may be treated regularly and safely with this product in small doses, over a period of years.

Animals↗
PubMed1995

Safety of high doses of a monoclonal antibody-purified factor IX concentrate. The Mononine Study Group.

This report summarizes safety and efficacy information among patients treated with high doses (> 75 U/kg) of a monoclonal antibody-purified factor IX concentrate [coagulation factor IX (human) monoclonal antibody purified)] in two clinical trials. One hundred infusions of this factor IX concentrate at doses > 75 U/kg were administered to 35 patients, six of whom had experienced thrombotic complications during previous treatment with prothrombin complex concentrate. Hemostasis in all patients was rated as "excellent," and there were no thrombotic complications.

Adult↗
PubMed1995

Comparison of six commercial plasma references for factor VIII, factor IX and von Willebrand factor. On behalf of the Subcommittee for Factor VIII and IX of the Scientific and Standardization Committee of the ISTH.

Six brands of normal reference plasma produced in the United States, with assigned assay values for factor VII and IX and, in four instances, ristocetin cofactor and van Willebrand antigen, were assayed in nine coagulation laboratories in academic institutions in the same country. Differences in mean assays of reference plasmas, as a percent of labelled potency, were significant and were greater than differences among laboratories. Standard methods of assigning potency to commercial reference plasmas are recommended.

Antigens↗