Search PubMed⌕ Search

Biomedical subjects

J Emmerich

Publications and source records attributed to J Emmerich.

At least 109 records · Page 6Linked to original sources
PubMed1995

Protein C infusion in a patient with inherited protein C deficiency caused by two missense mutations: Arg 178 to Gln and Arg-1 to His.

This paper reports the case of an adult patient with severe protein C(PC) deficiency. She had the first deep vein thrombosis when she was 14 years old and developed skin necrosis when oral anticoagulant treatment was started. The same sequence of thrombotic complications recurred several times. Analysis of the PC gene coding sequences allowed two mutations (Arg-1 to His and Arg 178 to Gln) to be identified in this compound heterozygote. Oral anticoagulant treatment during PC concentrate infusion and low-molecular-weight heparin administration was successful and uncomplicated.

Arginine↗
PubMed1995

Mechanism of protein C deficiency in a patient with arginine 358 alpha 1-antitrypsin (Pittsburgh mutation): role in the maintenance of hemostatic balance.

We recently described a new case of alpha 1-antithrombin (alpha 1-AT) Pittsburgh, a mutation that transforms alpha 1-AT into a potent inhibitor of thrombin. In contrast to the originally described patient, who had a severe hemorrhagic diathesis, our proband had only a mild bleeding tendency. The current article explores possible mechanisms for the relative hemostatic competence of our patient. The levels of both normal and mutant alpha 1-AT were similar to those of the previously reported case, as was the rise in plasma antithrombin level during an acute phase reaction. The level of protein C, however, was found on several occasions to be approximately 20% of normal. Family studies and examination of the patient's protein C gene on a denaturing gel failed to identify an abnormality. Moreover, the patient's protein C showed no abnormalities suggestive of faulty intracellular processing. However, the protein C in his plasma was for the most part in the activated form and bound to the mutant alpha 1-AT. Thus it is likely that the strong affinity of mutant alpha 1-AT for protein C leads to an increased turnover and thus to a low circulating level. A seeming flaw in that scenario is that the mutant alpha 1-AT also has a very high affinity for thrombin and might be expected therefore to block the activation of protein C. When thrombin was complexed with thrombomodulin (as it is when protein C is physiologically activated at the endothelial surface), mutant alpha 1-AT was far less able to inhibit thrombin than was the case for the free enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

A review of mutations causing deficiencies of antithrombin, protein C and protein S.

The mutations observed in patients with antithrombin and protein C deficiencies are mostly substitutions of one nucleotide, or deletions/insertions of fewer than 10 nucleotides in the exons and intron-exon junctions. These genomic abnormalities result in missense changes (involving aminoacids important for protein folding), aberrant polypeptide chains and/or premature termination codons, or abnormal splicing precluding DNA transcription. The number of mutations so far identified is such that it is difficult to use genomic DNA analysis for diagnostic purpose. However, identification of the gene defect can be useful in well-defined situations, such as the risk of homozygosity, and complex or ambiguous plasma phenotypes, which frequently occur in protein C deficiency. Protein S deficiency, the molecular bases of which have been less extensively studied, is due to micromodifications of the coding sequence in only half the cases investigated so far. The mechanisms involved in the remaining cases remain to be identified.

Alleles↗
PubMed1994

A phenylalanine 402 to leucine mutation is responsible for a stable inactive conformation of antithrombin.

In a South African family with antithrombin deficiency and unexplained thrombosis, genomic DNA analysis revealed a substitution of Phe 402 by Leu. This mutation involves an amino acid located in the carboxyterminal side of the antithrombin reactive loop and has already been observed in a French family (antithrombin Maisons-Laffitte). In both cases, the expression of the mutation is pleiotropic, i.e. results in a reduction in the circulating concentration of antithrombin and impairs both its anti-thrombin activity and its ability to bind heparin. The effect of a denaturing agent (sodium dodecyl sulfate) on the recognition of the plasma antithrombin by a polyclonal antibody was studied in an immuno-enzymatic assay. The Phe to Leu mutation decreased the sensitivity to denaturation, suggesting that the mutation increases the stability of the protein. Whether this stable conformation is due to a partial insertion of the amino-terminal side of the reactive loop, which would explain how both protease binding and heparin binding are affected, remains to be determined.

Adolescent↗
PubMed1994

First de novo mutations in the protein C gene of two patients with type I deficiency: a missense mutation and a splice site deletion.

In a series of 40 patients with symptomatic protein C deficiency, we identified two sporadic cases with novel mutations that probably affect gene expression. The mutations, a 5-bp deletion of the donor splice site of intron f (nucleotides 3455 to 3459) and a mutation of nucleotide 8523 in exon IX leading to the substitution of Ser 270 by Pro, were not found in the protein C gene of the patients' parents. Transmission of the paternal and maternal protein C alleles was apparently normal on the basis of frequent polymorphisms in exons I, VI, and VIII. We also checked the transmission of the chromosomal material by analyzing the beta-globin gene frameworks and three variable number of tandem repeats (VNTRs). By combining the results of intragenic polymorphism, VNTR and beta-globin gene framework analyses, we were able to exclude nonpaternity and confirm the de novo origin of the mutation.

Adult↗
PubMed1994

[A new cause of familial thrombophilia: resistance to the effect of activated protein C].

An examination of the cascade of events leading to coagulation emphasizes the importance of protein inhibitors. Deficiencies in these proteins have been implicated as playing a possible causal role in familial thrombo-embolic diseases. Recently the discovery of a probable deficiency in protein C cofactor, different from protein S, stimulated much research in this area. Protein C is a 461 amino acid vitamin K-dependent protein with a molar mass of 62,000 Daltons. After transduction the precursor protein is modified into an active form. Circulating protein C is then activated by proteolysis on the endothelial surface under the control of thrombomodulin-bound thrombin. Thus thrombin affects both procoagulation by activating factors V and VIII (and XI) and anticoagulation after being bound to thrombomodulin. Inactivation of factors V and VIII requires calcium, phospholipids and a C-protein cofactor, protein S. On the basis of clinical observations, it was hypothesized then confirmed that deficiency in a non-identified cofactor of protein C could explain resistance to the anticoagulating action of activated protein C. Purification of the plasma fraction carrying the cofactor activity led to the isolation of a protein which has all the biochemical properties of factor V. In addition, adding factor V to affected plasma has been shown to correct for resistance to activated protein C. But paradoxically, patients with resistance to the action of activated protein C have a normal level of factor V. The mutation responsible for activated protein C resistance was found to be a Gln for Arg mutation at position 506 of factor V. The implication of this mutation has been very recently confirmed and led rapidly to the development of molecular biology methods allowing its identification. At present, this new cause of familial hypercoagulable states can thus be identified with polymerase chain reaction and denaturing gradient gel electrophoresis. These advances have increased the number of identifiable hypercoagulable states, yet further work is needed since currently less than 10% of these diseases can be explained by deficiencies in one of the inhibitor proteins, antithrombin III, protein C or protein S.

Factor V↗
PubMed1994

Three novel mutations of antithrombin inducing high-molecular-mass compounds.

We have identified three novel mutations of the antithrombin (AT) gene in patients with thrombotic complications: a Cys 128 --> Tyr mutations, a G --> A mutation in the intervening sequence 4 (IVS4) 14 nucleotide 5' to exon 5, and a 9 bp deletion in the 3' end of exon 6 resulting in a short aberrant sequence after Arg 425. The latter mutation was associated with an Arg 47 --> His mutation in two compound heterozygous brothers. These three mutations led to the expression in the circulation of small amounts of inactive molecules with a high molecular mass in immunoblot analysis. In reducing conditions, these variant molecules had a normal molecular mass, which led us to postulate that these mutations prevent the formation of one intramolecular disulfide bond and allow the formation of intermolecular disulfide bonds. Plasma from a heterozygous patients bearing the Cys 128 --> Tyr mutation and from a compound heterozygote bearing the Arg 47 --> His mutation and the 9 bp deletion in exon 6 were passed through a heparin-sepharose column. In both cases a population of high-molecular-weight AT molecules with no binding affinity and no AT activity was separated from a population of normal molecules in the first patient, together with a population of molecules with a reduced binding affinity for heparin due to the substitution of Arg 47, in the compound heterozygote. The common feature of these three mutations is that they lead to partial misfolding and to the formation of intermolecular disulfide bonds with other plasma components, inducing the pleiotropic phenotypes observed.

Adolescent↗
PubMed1994

Molecular basis of antithrombin type I deficiency: the first large in-frame deletion and two novel mutations in exon 6.

We report three novel mutations accounting for cases of inherited type I antithrombin (AT) deficiency. Using the polymerase chain reaction (PCR) and direct sequencing of the coding sequences of the AT gene, we found one mutation in exon 4 and two in exon 6. A deletion of 105 bp causing an in-frame deletion of 35 amino acids between Tyr 240 and Gly 276 was found in exon 4. In a second kindred, deletion of two adenines in codon 412-413 introduced a frameshift and a stop codon at position 431. The last mutation was an insertion of ACCG in codon 387, generating a frameshift with a stop codon located at the normal position. The finding of a sequence repeat of nine residues located at the 5' and 3' ends of the deleted fragment might explain the 105 bp deletion by slippage and mispairing at the replication fork during DNA synthesis. The second mutation is the fourth described within a region of six amino acids (between Phe 408 and Arg 413), which seems to be a cluster of mutations. In this case, the presence of a double repeat sequence--TTCCT and AACA--flanking this region could be particularly favorable for slipped mispairing. These results confirm that human gene mutations are not random events but are strongly influenced by DNA flanking sequences.

Amino Acid Sequence↗
PubMed1994

Influence of six mutations of the protein C gene on the Gla domain conformation and calcium affinity.

The protein C Gla domain was studied in six families presenting a type II hereditary deficiency characterized by low activity in a coagulation assay and normal activity in an amidolytic assay. Five of these mutations, previously described by our group, affected Arg-5, Arg-1, Arg 229 and Ser 252. We report here the first natural Glu 7 to Asp mutation in a sixth family. We evaluated the binding of the mutated protein C to H11, a monoclonal antibody (mAb) known to recognize the sequence Phe4 to Arg9 of the Gla domain; the presence of calcium ions suppresses the recognition of this epitope by H11. Mutation of Arg229 to Gln and Ser252 to Asn did not modify the inhibition of protein C binding, whereas the Arg-1 to His mutation resulted in a loss of inhibition in the presence of CaCl2. This suggests that the protein C of this patient shows impaired carboxylation. The protein C from patients bearing the mutations Arg-5 to Trp, Arg-1 to Cys and Glu 7 to Asp bound poorly to H11 mAb, even in the absence of calcium ions. The calcium affinity of the Gla domain was studied by pseudo-affinity chromatography, in which protein C was successively eluted from a Mono Q column by CaCl2 10 mM and NaCl 0.6 M. Protein C from the patient bearing the Arg-5 to Asp mutation had a normal elution profile, suggesting that a modification of the propeptide cleavage site impairs the conformation of the Gla domain but not carboxylation.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Carboxyglutamic Acid↗