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J Riou

Publications and source records attributed to J Riou.

At least 37 records · Page 2Linked to original sources
PubMed1998

Haemoglobin J-Biskra: a new mildly unstable alpha1 gene variant with a deletion of eight residues (alpha50-57, alpha51-58 or alpha52-59) including the distal histidine.

Single point mutation, which accounts for 92% of the 700 known variants, is the most frequent genetic defect responsible for abnormal haemoglobins. Small deletions (or insertions) involving from one to five residues are also observed, but in only approximately 5% of cases. The remaining variants produce fusion or extended haemoglobins. A deletion of eight residues, which included the distal histidine and its neighbours (alpha50-57, alpha51-58 or alpha52-59), was found in Hb J-Biskra. This new alpha-chain variant was mildly unstable in vitro only and there was no haematological or biochemical evidence of haemolysis in the affected family members. 24 nucleotides were missing in a region of the alpha1 gene showing an identical sequence of eight nucleotides at both ends. Several starting points could therefore lead to the same nucleotide and aminoacid remaining sequence. This deletion is the largest up to now reported in a haemoglobin molecule which is expressed at an almost normal level in the red blood cell. Comparison of the DNA sequences near to the deleted (or inserted) regions in the various haemoglobins carrying this type of abnormality almost always revealed the presence of a sequence that was hypothesized to slow down progression of the replication fork, and of repeats that may lead to possible secondary structures favouring slipped mispairing.

Amino Acid Sequence↗
PubMed1998

Hb Godavari [alpha 95(G2)Pro-->Thr]: a neutral amino acid substitution in the alpha 1 beta 2 interface that modifies the electrophoretic mobility of hemoglobin.

Hb Godavari [alpha 95(G2)Pro-->Thr] was characterized independently in two families of different ethnic origin. The first case, found in the Netherlands, involved an Indian patient. The second one was identified a few months later in an African family from Mali, living in France. Hb Godavari is the fourth example of a substitution involving neutral residues at position alpha 95(G2). In all these variants the electrophoretic pattern suggested that the structural modification unmasks a charged residue buried in the alpha 1 beta 2 contact area. The oxygen affinity of this abnormal hemoglobin was approximately 10% higher than that of Hb A; in the absence of 2,3-diphosphoglycerate, its cooperativity was moderately decreased, suggesting a slightly unstable T state.

Adult↗
PubMed1998

HB Les Andelys [alpha83(F4)LEU-->PRO]: a new moderately unstable variant.

Hb Les Andelys [alpha83(F4)Leu-->Pro] is a mildly unstable variant that was found during glycated hemoglobin measurement in a French family. In this hemoglobin molecule the affected site, in the alpha chain, and the amino acid substitution are identical to those of Hb Santa Ana, an unstable beta chain variant. The structural abnormality was demonstrated by protein chemistry methods, involving, in addition to the classical techniques, a selective precipitation of the abnormal hemoglobin by isopropanol and a mass spectrometry analysis of the alphaT-9 peptide following carboxypeptidase digestion. DNA sequencing demonstrated that the mutation was CTG-->CCG at codon 83 of the alpha2 gene.

Amino Acid Sequence↗
PubMed1997

Structural and functional studies of hemoglobin Moabit (alpha 86(F7) Leu-->Arg.

An abnormal hemoglobin fraction was detected on high performance liquid chromatography profile performed for the measurement of glycated hemoglobin in a 55-year-old caucasian patient. The structural and functional studies were performed by standard techniques. Separation of hemoglobins by alkaline electrophoresis and by IEF revealed a slightly more rapid fraction than does Hb S. By acid electrophoresis, no abnormal Hb fraction could be observed. Separation of globin chains by electrophoresis demonstrated an alpha-chain variant and by chromatography, a fraction which eluted between beta and gamma globin chains. Tryptic digests and amino acid analysis have demonstrated a previously described substitution of Leu-->Arg alpha 86(F7).

Blood Protein Electrophoresis↗
PubMed1997

Cation-exchange HPLC evaluated for presumptive identification of hemoglobin variants.

A battery of relatively simple tests allows the presumptive identification of hemoglobin (Hb) variants, making unnecessary structural analysis by protein chemistry methods or DNA sequencing. The primary step in this strategy involves the use of a matrix of electrophoretic mobilities obtained under various experimental conditions. This leads to an unambiguous result in approximately 90% of the cases. Additional tests are required to characterize with more confidence the remaining 10%. We describe here the use of cation-exchange HPLC on the Bio-Rad Variant automated analyzer with the "beta Thalassemia Short" program. By comparing the elution time of 125 human Hb mutants, we found that some variants with almost identical pI values or produced by the same type of amino acid substitution displayed different elution times. We present several examples in which use of the HPLC profile helped establish the diagnosis.

Cations↗
PubMed1996

Perfusion chromatography on reversed-phase column allows fast analysis of human globin chains.

Human globin chain analysis provides important information on the genetics and molecular pathophysiology of hemoglobinopathies. We propose using perfusion chromatography on the reversed-phase stationary phase to perform these studies. The technique, herein described, involves a high-velocity flow of the mobile phase through a porous chromatographic stationary phase made of microspheres of poly(styrene-divinylbenzene) having throughpores of 6000-8000 A diameter with short diffusive pores of 500-1000 A diameter connected to them. The composition of fetal hemoglobin (Ggamma:Agamma ratio) is determined, using this method, as an order of magnitude faster than with conventional HPLC. Elution is performed by developing a linear gradient of acetonitrile at a flow rate of 3 ml/min (or more), easily obtained on any HPLC machine. Analyses may be done on samples containing as low as 3.0% Hb F. Results are similar to those obtained with the reference HPLC technique, which uses a C4 column. In addition, reversed-phase perfusion chromatography, using a shallow curvilinear gradient, may help in the characterization of Hb variants. This technique allowed us to discriminate several alpha and beta chain mutants from variants that have closely similar patterns of electrophoretic mobilities.

Chromatography↗
PubMed1995

Geographic distribution of 119 alleles of the alpha and beta globin genes detected in 432 French Caucasian carriers of haemoglobin variant.

The French population is the result of mixing of different peoples including the Celts, Saxons, Germans, Italians and Hispanics. Between 1981 and 1993 patients were selected during investigations in France for haematological disorders associated or otherwise with the presence of a haemoglobin (Hb) variant. Further carriers of abnormal Hb were identified by HPLC measurement of glycated Hb in diabetics and by neonatal screening. Four-hundred and thirty-two subjects were found to be heterozygous for one of the 119 different alpha and the beta gene alleles encountered. These variants were characterised by a combination of 6 electrophoretic methods and in some cases by protein structure determinations. Some mutants reflected the population movements in and into France. A few mutants are frequently described in the French Caucasian population: Hb Lepore Boston, Hb D Punjab, whereas others appear to be anthropological markers. Hb Winnipeg has only been found in the West of France (Normandy); Hb J Baltimore is mainly found in French subjects of Spanish origin. Several cases of sporadic and previously undescribed mutations of Hb were identified. The last immigration waves from Africa and Asia appear to have contributed to the evolution of the pattern of haemoglobinopathies in the French population (Hb S, Hb O Arab or Hb C).

Alleles↗
PubMed1994

Hemoglobin variants in North Africa.

The populations of Morocco, Algeria, and Tunisia are composed of different ethnic groups including Arabs, Berbers, Sub-Saharan Africans, Europeans, and Turks. Between 1981 and 1991, we studied more than 3,000 individuals from these North African countries. One-hundred and eighty-one carried one (or more) unusual hemoglobin variant(s) other than Hb S and Hb C which are the most frequent variants in these countries. Each of these 181 individuals was heterozygous for at least one of the 49 abnormal alpha or beta alleles identified by electrophoretic and/or structural studies, and some homozygotes were detected. A few mutants are common in North Africa: Hb O-Arab, Hb D-Punjab and Hb G-Philadelphia. Other mutants encountered in European or African populations are found in relatively few North African families. The observed polymorphisms in the populations of North Africa probably result largely from their complex ethnic origins.

Algeria↗
PubMed1993

Hb Saint Nazaire (beta 103[G5]Phe-->Ile): a new example of polycythemia due to a hemoglobin variant with increased oxygen affinity.

Hb Saint Nazaire [beta 103 (G5) Phe-->Ile] was found in four apparently unrelated French families. The five patients carrying this hemoglobin have been detected because of a moderate erythrocytosis. The structural abnormality of Hb Saint Nazaire concerns the same residue as in Hb Heathrow [beta 103 (G5) Phe-->Leu). A comparative functional study between these two variants showed that the increase in oxygen affinity is much lower in Hb Saint Nazaire than in Hb Heathrow. The replacement of phenylalanine G5, which is localized within the heme pocket, by a leucine abolishes several contacts between the heme and the globin and leads to an environment of the heme having some similarities with that observed in myoglobin. In contrast, the replacement of G5 by an isoleucine is likely to introduce less structural modifications.

Adolescent↗
PubMed1993

Hb Melusine [alpha 114(GH2)Pro-->Ser]: a new neutral hemoglobin variant.

Hb Melusine [alpha 114(GH2)Pro-->Ser] was found in an Algerian patient during a systematic screening for hemoglobinopathies performed in Luxembourg. The abnormal hemoglobin was suspected when a thickening of the Hb A band was observed by isoelectrofocusing. The mutant hemoglobin was silent in all other electrophoretic methods used for presumptive diagnosis with the exception of globin electrophoresis in the presence of Triton X-100. This technique revealed an alpha chain considerably more hydrophobic than normal. The structural abnormality of Hb Melusine concerns position alpha 114(GH2) that belongs to a cluster of hydrophobic residues localized in the N-terminal half of the alpha T-12b tryptic peptide. It has been shown in the case of another variant of that position (Hb Nouakchott), that the replacement of the Pro GH2 by a Leu was responsible for a dramatic increase in the retention time of the alpha polypeptide chain during reversed phase high performance liquid chromatography, much higher than that reported for similar substitutions in other regions of the hemoglobin molecule.

Adult↗
PubMed1993

Hb Val de Marne [alpha 133(H16)Ser-->Arg]: a new hemoglobin variant with moderate increase in oxygen affinity.

Hb Val de Marne [alpha 133(H16)Ser-->Arg] was found in a French family during a neonatal hemoglobinopathy screening program. The abnormal hemoglobin was found, within a few months interval, in two newborn children who were first cousins. In the children as well as in the parents carrying this hemoglobin variant, the red cell parameters were normal. Hb Val de Marne, isolated by isoelectrofocusing, displayed a slightly higher auto-oxidation rate than Hb A. Its oxygen affinity was increased 1.7-fold in comparison to that of Hb A. The heterotropic effects were normal.

Adult↗
PubMed1992

Rapid molecular characterization of mutations leading to unstable hemoglobin beta-chain variants.

Characterization of unstable hemoglobins by protein analysis is often difficult. However, it is facilitated by DNA analysis, especially in the case of hyperunstable beta-chain variants, which produce a beta-thalassemia phenotype. We have applied an efficient strategy to the detection of such variants at the DNA level, based on computer-designed denaturing gradient gel electrophoresis (DGGE) of amplified DNA fragments. This approach makes it possible to detect any anomaly in the beta-globin gene. We describe the use of the DGGE method for rapid characterization of beta-chain variants and report a new missense mutation in the beta-globin gene third exon, beta 127 CAG-CGG/Gln-Arg, which is responsible for the synthesis of a highly unstable hemoglobin.

Adolescent↗