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Biomedical subjects

J C Deybach

Publications and source records attributed to J C Deybach.

At least 73 records · Page 4Linked to original sources
PubMed1993

Ferrochelatase structural mutant (Fechm1Pas) in the house mouse.

The molecular basis of an inherited defect of ferrochelatase in mouse (Fechm1Pas/Fechm1Pas, described by Tutois et al., 1991, J. Clin. Invest. 88:1730-1736) was investigated. cDNA clones encoding ferrochelatase, isolated by amplification of the mRNA from the liver of a mutant mouse using the polymerase chain reaction, were sequenced by the dideoxynucleotide chain-termination method. All the clones carried a T to A transversion at nucleotide 293, leading to a methionine to lysine substitution at position 98 in the protein (mutation M98K). Hybridization with allele-specific oligonucleotides (ASOs) confirmed the mutation at the cDNA and genomic levels. Finally, expression of the mutant ferrochelatase protein in E. coli demonstrated a marked deficiency in activity in agreement with the activity of the deficient enzyme in vivo. This Fechm1Pas/Fechm1Pas mutant mouse represents a useful model for studying the pathophysiological feature of the human disease and the first accessible model for gene therapy in the field of porphyrias.

Animals↗
PubMed1993

High prevalence of a point mutation in the porphobilinogen deaminase gene in Dutch patients with acute intermittent porphyria.

Acute intermittent porphyria (AIP) is an autosomal dominant disease characterized by a deficiency of porphobilinogen deaminase (PBGD). Up to now 14 different mutations have been described. In an effort to investigate the molecular epidemiology of AIP we have undertaken a systematic study of different exons of the PBGD gene from a large number of unrelated patients. Here, exon 8 from 82 unrelated Dutch and French AIP patients was examined using single strand confirmation polymorphism analysis (SSCP) after polymerase chain reaction (PCR) amplification. A single base mutation, C to T, at position 346 of the sequence coding for PBGD was observed in 15 Dutch families but in only 1 French family. A simple PCR assay is described to facilitate the diagnosis of this common mutation at the DNA level.

Base Sequence↗
PubMed1993

Decreased nocturnal plasma melatonin levels in patients with recurrent acute intermittent porphyria attacks.

Acute intermittent porphyria (AIP) is a hereditary disease characterized biochemically by a defect in the heme pathway enzyme porphobilinogen deaminase. There is wide variability in the neurologic clinical expression of AIP, and the disorder remains latent in most gene carriers. The natural history of the disease and results in a porphyric rat model suggest a significant relationship between tryptophan metabolites and clinical expression of the disease. In the present study, we examined urine and blood tryptophan metabolite levels in AIP women before, during and after acute attacks and treatment by heme arginate. Heme arginate treatment promptly decreased total tryptophan levels (from 69 +/- 9, to 44 +/- 5, mean +/- SEM, mumole/l, p < 0.001), serotonin blood levels (from 629 +/- 103, to 356 +/- 80, nmole/l, p < 0.01) and the urinary excretion of 5-HIAA (from 3.9 +/- 0.6, to 2.2 +/- 0.4, mumole/mmole creatinine, p < 0.01). The plasma level of melatonin was found much lower than the normal control level at night (86.2 +/- 70.3, vs the normal range, 409 +/- 78.9, pmole/l +/- SEM) and day time (38.8 +/- 22.0, vs 75 +/- 13.7). Heme arginate treatment did not influence melatonin levels. Our results support the involvement of abnormal tryptophan metabolism in the pathophysiology of AIP acute attacks. Low melatonin plasma levels in porphyric women suggest that the defect of the pineal hormone may be responsible for the recurrent aspect of porphyric attacks. A desynchronization of biological rhythms in AIP patients may increase the inducibility of hepatic ALA synthase to environmental risk factors and, specially, to sex steroid hormones.

Adult↗
PubMed1993

[Acute attacks of hepatic porphyria: specific treatment with heme arginate].

Severe hepatic porphyrias (acute intermittent porphyria, variegate porphyria and hereditary coproporphyria) are hereditary diseases. Each type of porphyria is the result of a specific decrease in the activity of one of the enzymes of heme biosynthesis. Acute attacks are very serious: the abdominal pains are severe and the neurological manifestations can lead to death or incomplete recovery with irreversible sequelae (usually paralysis). Since 1985, the prognosis of acute attacks has been greatly improved by the introduction of heme-arginate. The 69 acute attacks (30 patients, 4 men and 26 women) that we treated with heme-arginate between 1988 and 1991 are described in this report. All patients were infused with 250 mg/d of heme-arginate for 4 days: the mean duration of abdominal pain was 2.5 days (SD 0.72). For 95 p. 100 of the attacks, the total hospitalization time was 5 days or less; side effects were very minor. In every case, a favorable response was dependent upon the early initiation of heme therapy.

Acute Disease↗
PubMed1992

Heterogeneity of mutations in the uroporphyrinogen III synthase gene in congenital erythropoietic porphyria.

Congenital erythropoietic porphyria (CEP) or Günther's disease is an inborn error of heme biosynthesis transmitted as an autosomal recessive trait and characterized by a profound deficiency of uroporphyrinogen III synthase (UROIIIS) activity. We have previously described two missense mutations in the UROIIIS gene, confirming that the primary defect responsible for CEP is a structural alteration of this gene. We have extended our work to 5 additional unrelated families. Two new point mutations, a deletion and an insertion have been found in the messenger RNA. Our study shows that a molecular heterogeneity of the mutations exists in Günther's disease. One mutation (C73R), however, appears to be more frequent than the others. Finally, the different normal and mutated proteins have been expressed in Escherichia coli to determine the consequence of the mutations on the enzyme activity.

Amino Acid Sequence↗
PubMed1992

Denaturing gradient gel electrophoresis for rapid detection of latent carriers of a subtype of acute intermittent porphyria with normal erythrocyte porphobilinogen deaminase activity.

Acute intermittent porphyria is an autosomal dominant disorder defined by a partial deficiency of porphobilinogen deaminase (EC 4.3.1.8). Clinical manifestations of the disease are characterized by acute attacks of neurological dysfunction often linked to environmental factors. Early diagnosis of gene carriers is important in the prevention of attacks and is usually achieved by determining the porphobilinogen deaminase activity in erythrocytes. However, in a subtype of acute intermittent porphyria, the enzymatic defect is restricted to nonerythropoietic cells. Different mutations have already been described that account for this phenotype in two unrelated families. We previously detected asymptomatic carriers by using mutation-specific probes after in vitro amplification of the target DNA sequence. In this study, we investigated the DNA of eight unrelated subjects with the same subtype of acute intermittent porphyria by using the polymerase chain reaction, with subsequent analysis of the amplified products by denaturing gradient gel electrophoresis. Five of these patients shared the same single-base change. This technique was quite simple and efficient for detecting asymptomatic carriers. Importantly, it is potentially useful for studying families with the same phenotypic subtype of the disease and possibly different mutations in the same DNA region.

Base Sequence↗
PubMed1991

Human erythropoietic protoporphyria: two point mutations in the ferrochelatase gene.

The molecular basis of the ferrochelatase defect responsible for human Erythropoietic Protoporphyria (EPP), a usually autosomal dominant disease, was investigated in a family with an apparently homozygous patient. Two mutations of the ferrochelatase gene were identified by sequencing the proband's cDNA after in vitro amplification of the mRNA and subcloning of the amplified products. One mutation results from a G to T transition at nucleotide 163 which produces a glycine to cysteine substitution at amino-acid residue 55 (G-55-C). The other one was a G to A change at nucleotide 801, leading to a methionine to isoleucine substitution at amino-acid residue 267 (M-267-I). This EPP patient was then double heterozygous and as expected each of his parents carried one of the mutations. A second similar EPP patient was screened for these mutations with negative results, showing a genetic heterogeneity in EPP.

Adult↗
PubMed1991

Erythropoietic protoporphyria in the house mouse. A recessive inherited ferrochelatase deficiency with anemia, photosensitivity, and liver disease.

A viable autosomal recessive mutation (named fch, or ferrochelatase deficiency) causing jaundice and anemia in mice arose in a mutagenesis experiment using ethylnitrosourea. Homozygotes (fch/fch) display a hemolytic anemia, photosensitivity, cholestasis, and severe hepatic dysfunction. Protoporphyrin is found at high concentration in erythrocytes, serum, and liver. Ferrochelatase activity in various tissues is 2.7-6.3% of normal. Heterozygotes (+/fch) are not anemic and have normal liver function; they are not sensitive to light exposure; ferrochelatase activity is 45-65% of normal. Southern blot analysis using a ferrochelatase cDNA probe reveals no gross deletion of the ferrochelatase gene. This is the first spontaneous form of erythropoietic protoporphyria in the house mouse. Despite the presence in the mouse of clinical and biochemical features infrequent in the human, this mutation may represent a model for the human disease, especially in its severe form.

Anemia, Hemolytic↗
PubMed1991

Molecular heterogeneity of acute intermittent porphyria: identification of four additional mutations resulting in the CRIM-negative subtype of the disease.

Four mutations of the porphobilinogen (PBG) deaminase gene that result in cross-reacting immunological material (CRIM)-negative forms of acute intermittent porphyria (AIP) have been identified by in vitro amplification of cDNA from patients and by cloning of the amplified products in a bacterial expression vector. One mutation is a single base deletion which causes a frameshift and which is expected to result in the synthesis of a truncated protein. Two other mutations consist of single base substitutions and lead to amino acid changes. The fourth mutation is a single base substitution producing an aberrant splicing and resulting in an mRNA which would encode a protein missing three amino acids. DNAs from 16 unrelated CRIM-negative AIP patients were screened for the presence of these four mutations, by hybridization with oligonucleotides specific for each of the mutations, but none of the four mutations was identified in additional patients. The results indicate that mutations responsible for CRIM-negative AIP are highly heterogenous.

Amino Acid Sequence↗
PubMed1990

Point mutations in the uroporphyrinogen III synthase gene in congenital erythropoietic porphyria (Günther's disease).

Congenital erythropoietic porphyria (Günther's disease) is a rare disorder of heme biosynthesis inherited in an autosomal recessive fashion. The molecular abnormality responsible for the characteristic defect in uroporphyrinogen III synthase activity was investigated in two patients. For the first patient, complementary DNA was specifically amplified using the polymerase chain reaction and subsequently cloned and sequenced. Data obtained revealed the coexistence of two distinct point mutations: a T to C change in codon 73 (arginine in place of a cysteine) and a C to T change in codon 53 (leucine in place of a proline). The second case was studied by hybridization with allele specific oligonucleotides and was found to be homozygous for the same mutation in codon 53. These are the first mutations to be recognized in the uroporphyrinogen III synthase gene from congenital erythropoietic porphyria patients.

Alleles↗
PubMed1990

A retrospective study of a patient with homozygous form of acute intermittent porphyria.

In 1964 a child with an exceptional form of porphyria was described; she excreted persistently excessive amounts of delta-aminolaevulinic acid, porphobilinogen and uroporphyrin in her urine from early childhood. The biochemical profile resembled that of acute intermittent porphyria (AIP). The child died at the age of 8 years. Reinvestigation of some urine samples by HPLC revealed differences in comparison with urines of other patients with AIP. The clinical picture characterized by porencephaly and severe retardation in development was completely different from that of AIP. Her mother suffered from AIP but the father never had attacks. Investigations on blood and urine samples of the father showed that he also was affected. Due to the early onset in the index patient, its persistent character, and the fact that both parents are affected we postulate retrospectively to have diagnosed a case of homozygous or a double heterozygous AIP, hitherto undescribed.

Acute Disease↗
PubMed1990

Two different point G to A mutations in exon 10 of the porphobilinogen deaminase gene are responsible for acute intermittent porphyria.

Two mutations of the porphobilinogen (PBG) deaminase gene resulting in cross-reacting immunological material (CRIM) positive forms of acute intermittent porphyria (AIP) have been identified by in vitro amplification of cDNA and cloning of the amplified products in a bacterial expression vector. Both mutations resulted from G to A transitions in exon 10 of the gene and produced arginine to glutamine substitutions in the abnormal protein. Expression of mutant cDNA in Escherichia coli reveals that one but not the other of these amino acid changes results in a striking decrease of the optimal pH of the mutated enzyme. One or the other of these two mutations accounted for the defect causing AIP in six unrelated patients among the eight patients evaluated with the CRIM positive subtype of this disorder.

Acute Disease↗