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Y Nordmann

Publications and source records attributed to Y Nordmann.

At least 91 records · Page 5Linked to original sources
PubMed1989

The mouse porphobilinogen deaminase gene. Structural organization, sequence, and transcriptional analysis.

The porphobilinogen deaminase gene encodes the third enzyme of the heme biosynthetic pathway. This gene is expressed in a tissue-specific manner and gives rise to two isoenzymatic forms encoded by mRNA species differing in their 5' extremity. Recent studies in human demonstrated that the tissue-specific expression of the porphobilinogen deaminase gene is determined in erythropoietic cells, by the utilization of a specific promoter situated 3' to the housekeeping promoter used in other cell types. This results, through differential splicing, in the mutually exclusive presence of either exon 1 or exon 2 in mature mRNAs. Here, we report the cloning and sequencing of the porphobilinogen deaminase gene from mouse. The overall organization of the mouse gene is similar to that of the human one. In the housekeeping promoter, only a short stretch of homology is found including two potential Sp1 binding sites; in contrast, more extensive similarity appears in the erythroid-specific promoter including two motifs also found in globin gene, a CACCC box, and a recently described Ery F1 consensus binding sequence. We derived a set of single-stranded probes corresponding to different parts of the mouse gene to carry out a detailed analysis of the transcriptional unit in various cell types, using a run-on transcription assay on isolated nuclei. In liver cells, the first (non-erythropoietic) exon is more actively transcribed than parts of the gene situated downstream, suggesting that the elongation of transcripts is blocked within the 5' part of the first intron. In erythropoietic cells, the downstream promoter becomes activated; surprisingly, the initiation of transcription is also enhanced from the upstream (housekeeping) promoter and most of the transcripts initiated at the housekeeping promoter stop downstream of the first exon, between the two promoters.

Amino Acid Sequence↗
PubMed1989

A point mutation G----A in exon 12 of the porphobilinogen deaminase gene results in exon skipping and is responsible for acute intermittent porphyria.

We have determined the mutation in a patient with acute intermittent porphyria. The mRNA coding for porphobilinogen deaminase was reverse transcribed then the cDNA was enzymatically amplified in vitro. Upon sequencing of a polymerase chain reaction product of abnormal size we found that this fragment lacked exon 12 of the gene. We analysed a genomic fragment containing exon 12 and determined that the patient was heterozygous for a point mutation G A at the last position of exon 12. We propose that this base change is responsible for an abnormal processing of the mutant allele such that exon 12 is missing in the mature mRNA. The resulting aberrant mRNA encodes a truncated protein which is inactive but stable and can be detected using antibodies directed against the normal enzyme.

Acute Disease↗
PubMed1989

Purification and properties of mouse liver coproporphyrinogen oxidase.

Coproporphyrinogen oxidase was purified to homogeneity from mouse liver. The specific activity of the pure enzyme was 3500 nmol.h-1.mg-1; its apparent molecular mass (35 kDa) was confirmed by immunological characterization of the enzyme in a trichloroacetic-acid-precipitated total-liver-protein extract. The native enzyme appeared to be a dimer of 70 kDa as determined by gel filtration under nondenaturating conditions. The Km value for coproporphyrinogen III was 0.3 microM. The purified enzyme was activated by neutral detergents and phospholipids (affecting both Vmax and Km) but inhibited by ionic detergents. Reactivity toward sulfhydryl agents suggested the possible involvement of (an) SH group(s) for the activity. When compared to the previously purified coproporphyrinogen oxidases (from bovine liver and yeast), the mouse liver coproporphyrinogen oxidase appears to share many common catalytic properties with both enzymes. However, its apparent molecular mass is very different from that of the bovine liver enzyme (71.6 kDa) but identical to that found for the yeast (Saccharomyces cerevisiae) enzyme.

Amino Acids↗
PubMed1989

[Anesthesia and hepatic porphyria].

Three of the acute hepatic porphyrias, acute intermittent porphyria, variegata porphyria and hereditary coproporphyria, are characterized by an idiosyncratic reaction to many common drugs; the resulting excessive excretion of porphyrin precursors is responsible for episodes of acute neurological dysfunction. This review aimed to focus the attention of the anaesthesiologist on the porphyrinogenic properties of all the drugs used in anaesthesia and intensive care. An outline of the chemistry of porphyrins and the enzymatic pathways were recalled, so as to place the acute porphyrias in their proper perspective. There follows a reminder of the clinical aspect of acute porphyric crises. The part played by drugs is then assessed from clinical and laboratory data concerning their porphyrinogenicity. Those drugs for which there is conflicting evidence regarding their safe use in porphyric patients are discussed: propofol, ketamine, benzodiazepines, etomidate, local anaesthetics. Recommendations supported by clinical and experimental data are given, especially the results obtained with the chick embryo liver model. Treatment of the acute crisis is provided, with particular emphasis on the use of haematin. The anaesthetic management of hepatic porphyric patients is described. Those drugs which are well-known porphyrinogenic compounds in the chick embryo liver must be excluded from use for anaesthesia in the porphyric patients, even if they have been observed to be innocuous in rare cases of asymptomatic patients. Finally, recommendations for anaesthesia in symptomatic cutanea porphyria are given.

Alcuronium↗
PubMed1989

Tissue-specific splicing mutation in acute intermittent porphyria.

An inherited deficiency of porphobilinogen deaminase [porphobilinogen ammonia-lyase (polymerizing), EC 4.3.1.8] in humans is responsible for the autosomal dominant disease acute intermittent porphyria. Different classes of mutations have been described at the protein level suggesting that this is a heterogeneous disease. It was previously demonstrated that porphobilinogen deaminase is encoded by two distinct mRNA species expressed in a tissue-specific manner. Analysis of the genomic sequences indicated that these two mRNAs are transcribed from two promoters and only differ in their first exon. The first mutation identified in the human porphobilinogen deaminase gene is a single-base substitution (G----A) in the canonical 5' splice donor site of intron 1. This mutation leads to a particular subtype of acute intermittent porphyria characterized by the restriction of the enzymatic defect to nonerythropoietic tissues. Hybridization analysis using oligonucleotide probes after in vitro amplification of genomic DNA offers another possibility of detecting asymptomatic carriers of the mutation in affected families.

Acute Disease↗
PubMed1989

Molecular analysis of acute intermittent porphyria in a Finnish family with normal erythrocyte porphobilinogen deaminase.

Porphobilinogen deaminase, the third enzyme of the haem biosynthetic pathway, is encoded by two distinct mRNA species expressed in a tissue-specific manner from a single gene. These two mRNAs are transcribed from two promoters and only differ in their first exon. An inherited deficiency or porphobilinogen deaminase in man is responsible for the autosomal dominant disease acute intermittent porphyria. Different classes of mutations have been described at the protein level suggesting that this is a heterogeneous disease. In the present report, we describe the molecular abnormality responsible for a variant form of acute intermittent porphyria where the enzyme defect is restricted to non-erythroid cells. Upon cloning and sequencing the mutant allele of a patient from a large Finnish kindred, a single-base substitution within the 5'-splice donor sequence of intron 1 was found at the last position of exon 1 (CG----CT). The identification of this mutation allowed us to detect asymptomatic gene carriers among family members using in vitro amplification of DNA and hybridization of the target sequence to allele-specific oligonucleotides.

Ammonia-Lyases↗
PubMed1988

Prevalence of the 281 (Gly----Glu) mutation in hepatoerythropoietic porphyria and porphyria cutanea tarda.

The prevalence of the 281 (Gly----Glu) mutation in hepatoerythropoietic porphyria (HEP) was investigated by the use of hybridization with a synthetic oligonucleotide probe. The mutation was found in HEP-affected members of two unrelated families from Spain, but was absent in two other patients from Italy and Portugal who also had HEP. Moreover, this mutation was not detected in 13 unrelated cases of familial (type II) porphyria cutanea tarda.

Carboxy-Lyases↗
PubMed1988

Radiological features in congenital erythropoietic porphyria (Gunther's disease). Report of 3 cases.

Gunther's disease or congenital erythropoietic porphyria is a rare and severe disorder comprising cutaneous and haemolytic symptoms. Photocutaneous lesions are responsible for scleroderma-like calcifications and deformities of the extremities visible on X-rays. Hemolytic manifestations lead to diffuse major osteopenia. Soft tissue calcifications of the fingers can be seen even in young patients. One case reported here is the first illustration of intracranial calcifications located on dura-mater and calvarium.

Bone Diseases, Metabolic↗
PubMed1987

DNA polymorphism of human porphobilinogen deaminase gene in acute intermittent porphyria.

A common two-allele MspI restriction fragment length polymorphism of the human erythroid porphobilinogen (PBG)-deaminase gene was investigated in 33 unrelated patients with acute intermittent porphyria (AIP) and 20 controls. The polymorphism was tightly linked (lod score 3.14; no recombinants) to the locus for AIP as identified by measurement of erythrocyte PBG-deaminase activity. The frequency of the polymorphism in the AIP patients did not differ significantly from that in the controls. No common polymorphisms for eight other restriction endonucleases were found in either group. In 30 of the AIP patients no crossreacting immunological material (CRIM) was produced by the mutant PBG-deaminase allele. The MspI polymorphism enabled each PBG-deaminase allele to be distinguished in subjects heterozygous for the polymorphism; thus a major gene deletion was excluded as the cause of the CRIM-negative mutation in all of the 18 families that contained an affected CRIM-negative individual heterozygous for the polymorphism. In suitable families, the MspI polymorphism provides a more certain way of identifying carriers of the AIP gene than current enzymatic methods and major gene deletions are unlikely to be present in more than a small proportion of the commonest type of AIP, the CRIM-negative form.

Acute Disease↗
PubMed1987

Ferritin synthesis in differentiating Friend erythroleukemic cells.

We have investigated the regulation of ferritin synthesis during induction of Friend erythroleukemic cells by dimethyl sulfoxide. Northern blot analysis shows that mouse ferritin H and L mRNAs each contain approximately 1.1 kilobases. The levels of both mRNAs increase after addition of dimethyl sulfoxide in a biphasic manner. After a sharp rise in the first 6 h, the levels decline and then rise again over the next 90 h. These increases in mRNA levels reflect increased transcription of both mRNAs. Analysis of ferritin subunit synthesis surprisingly showed no corresponding increase in the rate of protein synthesis, suggesting that the additional mRNA was not in functional polysomes. These studies also indicated a novel processing of mouse ferritin H subunits. H subunits appear to be synthesized as a precursor of approximately 22,500. This form is not present in mature shells. Pulse-chase experiments indicated that the precursor is first processed to an intermediate form of 20,000 and then to the 18,000 component found in functional shells.

Animals↗
PubMed1987

[Drug risk of hepatic porphyria. Development of an animal experiment model].

Hepatic porphyrias (acute intermittent porphyria, coproporphyria, porphyria variegata and porphyria cutanea) are inherited diseases affecting porphyrin-heme metabolism in the liver. A situation analogous to the latent stage of human hepatic porphyria can be produced in chick embryos by injecting an inhibitor of ferrochelatase (the last enzyme in the heme biosynthesis pathway); the simultaneous injection of a porphyrinogenic drug (e.g. barbiturate) results in a strong increase of liver porphyrin levels, as is found in human hepatic porphyrias. This experimental model facilitates drug screening: drugs that are found to be porphyrinogenic in ovo are potentially dangerous to patients with hepatic porphyria and should be avoided.

Animals↗
PubMed1987

Tissue-specific expression of porphobilinogen deaminase. Two isoenzymes from a single gene.

Porphobilinogen deaminase (hydroxymethylbilane synthase; EC 4.3.1.8), the third enzyme of the heme biosynthetic pathway, catalyzes the stepwise condensation of four porphobilinogen units to yield hydroxymethylbilane, which is in turn converted to uroporphyrinogen III by cosynthetase. We compared the apparent molecular mass of porphobilinogen deaminase from erythropoietic and from non-erythropoietic cells by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and immune-blotting. The results indicate that two isoforms of porphobilinogen deaminase can be distinguished and differ by 2000 Da. Analysis of cell-free translation products directed by mRNAs from human erythropoietic spleen and from human liver demonstrates that the two isoforms of porphobilinogen deaminase are encoded by distinct messenger RNAs. We cloned and sequenced cDNAs complementary to the non-erythropoietic form of porphobilinogen deaminase encoding RNA. Comparison of these sequences to that of human erythropoietic mRNA [Raich et al. (1986) Nucleic Acids Res. 14, 5955-5968] revealed that the two mRNA species differ by their 5' extremity. From the mRNA sequences we could deduce that an additional peptide of 17 amino acid residues at the NH2 terminus of the non-erythropoietic isoform of porphobilinogen deaminase accounts for its higher molecular mass. RNase mapping experiments demonstrate that the two porphobilinogen deaminase mRNAs are distributed according to a strict tissue-specificity, the erythropoietic form being restricted to erythropoietic cells. We propose that a single porphobilinogen deaminase gene is transcribed from two different promoters, yielding the two forms of porphobilinogen deaminase mRNAs. Our present finding may have some relevance for further understanding the porphobilinogen deaminase deficiency in certain cases of acute intermittent porphyria with an enzymatic defect restricted in non-erythropoietic cells.

Ammonia-Lyases↗