Search PubMed⌕ Search

Biomedical subjects

J Delaunay

Publications and source records attributed to J Delaunay.

At least 73 records · Page 4Linked to original sources
PubMed1996

Molecular genetics of hereditary elliptocytosis and hereditary spherocytosis.

Red cells ow their mechanical properties, that is, their resistance and their elastic deformability, to a protein network that laminates the lipid bilayer and to proteins spanning the latter. All proteins are interconnected. Their structure, as well as the structure of the corresponding genes, will be outlined. Numerous mutations have allowed to reclassify hereditary elliptocytosis (HE) and poikilocytosis (HP), and, more recently, hereditary spherocytosis (HS) into well defined subsets of hereditary hemolytic anemias. HE stems from changes in the SPTA1, SPTB, EL1 and (exceptionally) GPYC genes that encode spectrin alpha- and beta- chains, protein 4.1 and glycophorin C/D, respectively. HS derives from altercations in the ANK1, EPB3 and ELB42 genes, encoding ankyrin, band 3 and protein 4.2, respectively, and also in the SPTA1 and SPTB genes. We will present a repertory of the known mutations. Innumerable polymorphisms will not be considered here, except for a few remarkable ones. Some general points must be stressed on. (a) Clinically conspicuous disorders are often the result of two alleles interacting in trans to one another. Whereas one allele causes moderate symptoms by itself, the other one is usually silent in the simple heterozygous (and exceptionally in the homozygous) state. As a result, the number of potentially pathogenic alleles is much more important than had been initially suspected. (b) The reduction or the loss of a protein within multiprotein assemblies are frequently encountered in red cell membrane genetic diseases; it leads to the disruption of the complexes with the possible disappearance of the other proteins than the mutated protein. (c) The above genes being also expressed in nonerythroid tissues, one starts finding multisyndromic conditions adding non-hematological manifestations to hemolysis. It is puzzling, though, that such situations are not more frequent. (d) In practice, the molecular diagnosis of HE and HS has reached a semi-routine stage that helps very much the paediatricians and haematologists.

Anemia, Hemolytic↗
PubMed1995

Genetic disorders of the red cell membranes.

The red cell membrane is comprised of a lipid bilayer studded with transmembrane proteins, and laminated by a protein network, the membrane skeleton, at the surface of the inner monolayer. The erythrocyte owes its mechanical properties to the membrane skeleton. Hereditary spherocytosis, hereditary elliptocytosis or poikilocytosis, Southeast Asian ovalocytosis are hereditary hemolytic anemias, due to mutations in the genes encoding ankyrin, the anion exchanger, spectrin, protein 4.1 or protein 4.2, which are main proteins of the membrane. Recent advances in the field have led to fundamental questions.

Anemia, Hemolytic, Congenital↗
PubMed1995

Hemoglobin Roanne [alpha 94(G1) Asp-->Glu]: a variant of the alpha 1 beta 2 interface with an unexpected high oxygen affinity.

In hemoglobin (Hb) Roanne, the aspartate residue alpha 94(G1) is replaced by a glutamic acid. This residue plays a key role in the structural changes affecting the alpha 1 beta 2 contact area during the deoxy- to oxy-state transition in the hemoglobin molecule. Aspartate alpha 94(G1) is involved in several contacts both in the deoxy- and oxy-structures. The most important of those is a hydrogen bond with asparagine beta 102 (G4), stabilizing the oxygenated structure. Alteration of this contact usually leads to a decrease in oxygen affinity. Hb Roanne is the first example in which an increased oxygen affinity was found as a result of a structural modification at this position. Functional data suggested that the mechanisms responsible for this altered property are a destabilisation of the T-structure and a modification of the allosteric equilibrium.

Aged↗
PubMed1995

A deletional frameshift mutation in protein 4.2 gene (allele 4.2 Lisboa) associated with hereditary hemolytic anemia.

We studied a 26-year-old Portuguese patient with recessively transmitted hereditary hemolytic anemia. Protein 4.2 was absent from red cell ghosts by Western blotting. Although the 4.2 mRNA was not detected in Northern blots, it was shown to be present by a procedure based on nested reverse transcription-polymerase chain reaction (RT-PCR). Partial nucleotide sequencing disclosed a one-nucleotide deletion at nt 264 (or 265): AAG GTG-->AAG TG, in codon 88 (or 89) belonging to exon 2. This change, defining allele 4.2 Lisboa, placed in frame the nonsense triplet that normally overlaps codons 136 and 137 (GTG ACC). This mutation, which abolishes an EcoNI site, was also found in the gene of the proband (homozygous state), her parents, and her brother (heterozygous state). Apart from anemia, the patient was free of clinical manifestations. Platelet membranes were also investigated using Western blots. Antibodies to red cell protein 4.2 showed a doublet (72 and 70 kD) both in the controls and the patient. This finding raises an interesting question concerning the relationship between this doublet and erythroid protein 4.2.

Adult↗
PubMed1995

Red cell membrane polypeptides under normal conditions and in genetic disorders.

Broadly speaking, the red cell membrane is comprised of --a cholesterol-rich phospholipid bilayer that is studded by a large number of trans-bilayer proteins, --of glycosylphosphatidylinositol-anchored proteins (GPI-proteins) standing outside, and --an important protein assembly, the erythrocyte or membrane skeleton, that laminates the inner surface of the bilayer. Among the trans-bilayer proteins, one finds the anion exchanger, the glycophorins, the glucose transporter, a variety of cation transporters and pumps, and of course proteins carrying the epitopes of many blood groups. Among the GPI-proteins, one encounters the acetylcholinesterase and the decay-accelerating factor (CD 55). Among the skeletal proteins, finally, one recognises spectrin, actin (and a number of actin-binding proteins other than spectrin: dematin, tropomyosin, tropomodulin, etc.), protein 4.1 and protein p55. Spectrin heterotetramer organizes into a bidimensional network with a hexagonal mesh on the average. This network is linked to trans-bilayer proteins, through the complex beta-spectrin-ankyrin-anion exchanger (+ protein 4.2) on the one hand and, on the other hand, through the triangular interaction between protein 4.1, glycophorin C and protein p55. The sequence of the above proteins and the exon-intron organisation of their genes are known in most cases. Many proteins have a widespread tissue distribution in the form of variants adapted to their local functions. Such variants may be the products of multigene families (anion exchanger, ankyrin, spectrin), or derive from a single gene (protein 4.1, protein 4.2), the transcripts of which undergo cell-specific alternative splicing. It has been established that many congenital haemolytic anaemias result from mutations altering the above-mentioned genes. We will provide two examples. Hereditary elliptocytosis stems from an array of mutations located at, or near the head-to-head self-association region of two spectrin alpha beta dimers, or from mutations which, most often, yield a reduction (heterozygous state) or the lack (homozygous state) of protein 4.1. The aggravation of elliptocytosis associated with alpha-spectrin mutations frequently yields poikilocytosis and usually stems from the occurrence, in trans, of a low expression allele, allele alpha LELY. Hereditary spherocytosis derives from mutations in the ankyrin gene (80% of the cases), the anion exchanger gene (10-15% of the cases), the protein 4.2 gene (rare cases) and the alpha- and beta-spectrin genes (rare cases). Anion exchanger mutations usually cause the decrease in this protein (heterozygous state).(ABSTRACT TRUNCATED AT 250 WORDS)

Anion Exchange Protein 1, Erythrocyte↗
PubMed1995

Hereditary xerocytosis: a report of six unrelated Spanish families with leaky red cell syndrome and increased heat stability of the erythrocyte membrane.

Hereditary xerocytosis (HX) is a rare haemolytic disease due to dehydrated red blood cells (RBCs). A unique feature of this syndrome is that affected members often show normal or near normal haemoglobin levels despite clinical and laboratory evidence of mild to moderate haemolysis. The diagnostic clue is the association of markedly increased RBC Na+ + K+ fluxes with low total cation (Na+ + K+) content. 11 patients of six unrelated families of Spanish origin with HX have been studied from clinical, genetical and biological points of view. In addition, we have investigated the sensitivity of RBC membrane to heat at three different incubation times (15, 30 and 60 min) and two different temperature values (46 degrees C and 49 degrees C). Under these conditions control RBCs (50 normal subjects) exhibited at 49 degrees C and 30 min a maximum of 30% fragmented RBCs. This value increased to 80% after 60 min of incubation. In contrast, patients with HX showed significantly lower percentages of fragmented RBCs at both 30 and 60 min of incubation (maximum 10% and 30%, respectively). In an attempt to determine if increased heat stability was unique to HX RBCs, several other congenital membranopathies with haemolytic anaemia were also studied. The degree of fragmentation, except in one case of HPP (which was strongly increased), did not differ from the control group. Electrophoretic studies of membrane proteins performed in RBCs of all the patients with HX did not explain any qualitative nor quantitative abnormality. In addition to its physiopathological interest, study of RBC heat stability, together with other haematological parameters (increased MCHC and decreased RBC osmotic fragility), may be useful for HX diagnosis, especially in laboratories which are not equipped to evaluate RBC membrane permeability.

Anemia, Hemolytic↗
PubMed1995

Band 3 Chur: a variant associated with band 3-deficient hereditary spherocytosis and substitution in a highly conserved position of transmembrane segment 11.

We studied a large Swiss family with dominantly inherited hereditary spherocytosis and band 3 (anion exchanger 1, AE1) deficiency. Band 3 cDNA was analysed by single-strand conformation polymorphism analysis and nucleotide sequencing. A new point mutation was found: G771D (GGC-->GAC). This change was present in all eight investigated patients but absent in four healthy members of the family. It is located at a highly conserved position in the middle of transmembrane segment 11, introducing a negative charge in a stretch of 16 apolar or neutral residues. None of the six amino-acid substitutions already known in this region as being associated with band 3 deficiency were recorded. To rule out any major transcriptional or post-transcriptional defect, we evaluated the amount of band 3 mRNA by RNase mapping using a band 3-protein 4.1 chimaeric probe. Similar mRNA amounts were present in patients and controls. Our results strengthen the view that some amino-acids, that are well conserved throughout the AE family, may be crucial for the insertion and/or the stabilization of band 3 within the lipid bilayer. At the present time, most of the mutations altering such residues are located in the C-terminal region of band 3.

Animals↗
PubMed1995

Ethnic distribution of allele alpha LELY, a low-expression allele of red-cell spectrin alpha-gene.

Allele alpha LELY is a low-expression allele of erythroid spectrin alpha-chain. It carries mutations both in exon 40 and intron 45 and is associated with partial skipping of exon 46. Allele alpha LELY remains asymptomatic by itself. In contrast, it enhances the expression level of deleterious alpha-alleles occurring in trans, and as such has clinical importance. The aim of this study was to evaluate the incidence of allele alpha LELY in various ethnic groups, i.e. Caucasians, African Blacks, Japanese and Chinese. Allele alpha LELY occurred in all groups investigated with a fairly uniform frequency: 31%, 21%, 20% and 22%, respectively. Mutations in exon 40 and intron 45 appeared linked to one another without exception. Partial skipping of exon 46 or the low-expression feature, whenever they could be assessed, were invariably observed. Allele alpha LELY appears to be an ancient and stable allele.

Alleles↗
PubMed1995

A point mutation in the protein 4.2 gene (allele 4.2 Tozeur) associated with hereditary haemolytic anaemia.

A recessively transmitted haemolytic anaemia associated with the lack of protein 4.2 was found in a Tunisian kindred. Trace amounts of this protein (72 kD component) became visible using high-sensitivity Western blots. Band 3 and ankyrin genes were excluded as candidate genes by linkage studies, and nucleotide sequencing of band 3 cytoplasmic domain cDNA revealed no alteration. In contrast, protein 4.2 gene contained in the homozygous state a mutation at position 310: CGA-->CAA (Arg-->Gln). This mutation defining allele 4.2 Tozeur was co-inherited with the disease. The mRNA encoding the variant protein was normal in size and approximately normal in amount. Recombinant protein 4.2 Tozeur bound normally to red cell IOVs but disclosed an increased susceptibility to proteolysis in vitro. We infer that the nearly total absence of protein 4.2 in the patients results from imbalance between destruction and synthesis of mutated protein 4.2 prior to its binding to the membrane.

Anemia, Hemolytic↗
PubMed1994

Mild elliptocytosis associated with the alpha 34 Arg-->Trp mutation in spectrin Genova (alpha I/74).

We report a new mutation responsible for nonhemolytic hereditary elliptocytosis (HE). The proband displayed an impaired spectrin self-association and an increase of the alpha I 74-kD fragment (alpha I/74 abnormality). The responsible mutation occurred in exon 2 of spectrin alpha-gene: alpha 34 Arg-->Trp (CGG-->TGG), defining spectrin Genova. In Trans to allele alpha Genova, the proband disclosed allele alpha LELY, a common low-expression allele of spectrin alpha-gene. It was recognized through particular peptide maps as well as characteristic mutations in exon 40 and intron 45, respectively. The father, who carried allele alpha Genova, but not allele alpha LELY, had a milder presentation. The sensitization of allele alpha Genova by allele alpha LELY was noticeable in the proband as compared with his father. Nevertheless, it was not as sharp as that observed with many other alpha I/74 HE alleles. Therefore, each alpha I/74 HE allele has a distinct intrinsic severity.

Alleles↗
PubMed1994

Abnormal expression of protein 4.1 in spermatozoa of infertile men with teratospermia.

Molecular defects responsible for morphologically abnormal spermatozoa (teratospermia) associated with male sterility are largely unknown. We report defective expression of protein 4.1, a cytoskeletal protein initially recognised in red cells. In some patients with severely amorphous sperm heads, protein 4.1 had an abnormal sub-cellular localisation (tail instead of head) and appeared as high-molecular-weight isoforms, especially a 135 kDa species instead of the 82 kDa isoform seen in fertile sperm. Because the 135 kDa isoform is characteristic of immature germ cells from testis, its presence in teratospermia suggests profoundly disturbed sperm differentiation.

Cytoskeletal Proteins↗
PubMed1994

A deletional frameshift mutation in spectrin beta-gene associated with hereditary elliptocytosis in spectrin Napoli.

We studied a clinically manifest, dominantly transmitted elliptocytosis in an Italian family. We found a new spectrin variant, designated spectrin Napoli. Its beta-chain was truncated in its C-terminal region (apparent MW 216 kD). It displayed a low expression level (15%). There was a 8 nt deletion: CTTTTGAGAAGT-->CTGT (nt 6255-6262), starting after codon 2053. This deletion was followed by a 54 nt (18 amino acids) missense sequence and terminated by the TGA triplet which normally overlaps codons 2074 and 2075 (CTTGAG). The overall length of the mutated beta-chain was comparable to that found in spectrin Nice, spectrin Tokyo and spectrin Tandil, which are other variants with truncated beta-chains; however, a distinct nonsense codon was used in spectrin Napoli.

Adult↗
PubMed1994

A variant of spectrin low-expression allele alpha LELY carrying a hereditary elliptocytosis mutation in codon 28.

Allele alpha LELY is a low-expression allele of the erythroid spectrin alpha-gene. It carries mutations in exon 40 (alpha V/41 polymorphism) and intron 45, respectively, and is associated with partial skipping of exon 46. The latter phenomenon is thought to impair the recruitment of alpha-chains by beta-chains, and would eventually account for the low-expression character. When it occurs in trans to an alpha-allele responsible for hereditary elliptocytosis (alpha HE allele; alpha HE/alpha LELY diplotype), allele alpha LELY enhances the severity of elliptocytosis. Because allele alpha LELY is widespread, we anticipated that it would occasionally carry HE determinants. These variants of allele alpha LELY will be designated alpha HE-LELY allele. The HE component was the known alpha 28 Arg-->His mutation. This alpha HE-LELY allele was investigated within the alpha HE-LELY/alpha LELY diplotype, a diplotype not described before. Except for the neonatal period, the presentation was mild. In a consistent manner, the alpha LELY component in cis of the alpha HE mutation counteracted the like component in trans.

Alleles↗
PubMed1994

Protein 4.1 deficiency associated with an altered binding to the spectrin-actin complex of the red cell membrane skeleton.

Protein 4.1 has been defined as a major component of the subcortical skeleton of erythrocytes. It binds the spectrin--actin scaffold through a 10-kD internal domain. This binding requires an essential 21-amino acid sequence motif, Motif I, which is retained by alternative splicing at the late stage of erythroid differentiation. We here analyze the molecular basis of heterozygous 4.1(-) hereditary elliptocytosis, associated with protein 4.1 partial deficiency, in nine related French families. cDNA sequencing revealed a single codon deletion (AAA) resulting in a lysine residue deletion within the 10-kD binding domain, 3' of Motif I. The mutated allele was designated allele 4.1 Aravis. In order to assess the functional effect of the codon deletion, recombinant 10-kD constructs were made and various binding assays were performed using spectrin, purified spectrin-actin complex, or red cell membranes. These experiments demonstrated that the deletion of the Lys residue clearly prevents the binding capacity. Similar results were obtained with a construct containing the Lys residue but lacking Motif I. These data strongly suggest that the binding site to the spectrin-actin complex must contain the Lys 447 (or 448), and therefore resides not only on Motif I but extends 3' of this essential motif.

Actins↗
PubMed1993

Elliptopoikilocytosis associated with the alpha 469 His-->Pro mutation in spectrin Barcelona (alpha I/50-46b).

We present two Spanish children with hereditary elliptopoikilocytosis. The mother displayed a symptomless elliptocytosis. Spectrin maps showed the alpha I/50-46b abnormality in the mother and in the children. The change was more conspicuous in the children than in the mother. The father carried the alpha V/41 allele, which is a common allele endowed with low expression. The alpha V/41 allele was also present in the children accounting for the much more severe expression of the alpha I/50-46b variant. The responsible mutation yielding the latter appeared to be the alpha 469 His-->Pro substitution (CAT-->CCT), which is a novel abnormality. The corresponding spectrin was designated spectrin Barcelona. As is often the case in hereditary elliptocytosis or poikilocytosis related to alpha-spectrin variants, the change involved a helix 3; namely, helix 3 of repeating segment alpha 5.

Alleles↗
PubMed1993

Evidence that red blood cell protein p55 may participate in the skeleton-membrane linkage that involves protein 4.1 and glycophorin C.

Human erythrocyte p55 is a peripheral membrane protein that contains three distinct domains in its primary structure: an N-terminal domain, an SH3 motif, and a C-terminal guanylate kinase domain. We used naturally mutated red blood cells (RBCs) with primary genetic defects resulting in the absence of protein 4.1 (4.1[-] hereditary elliptocytosis) or glycophorin C (Leach elliptocytosis). The absence of either protein was associated with the absence of p55. On a stoichiometric basis, the reduction in glycophorin C (about 80%) was concomitant to the lack of p55 in RBCs devoid of protein 4.1. Similarly, the reduction of protein 4.1 (about 20%) was equivalent to the absence of p55 in RBCs devoid of glycophorin C. These correlations suggest that p55 is associated, in precise proportions, with the protein 4.1-glycophorin-C complex, linking the skeleton and the membrane. The protein 4.1-glycophorin-C cross-bridge is known to be critically important for the stability and mechanical properties of human RBC plasma membrane. Because isoforms of protein 4.1, glycophorin C, and p55 exist in many tissues, these results provide evidence of a linkage between the skeleton and the membrane that may have implications in many nonerythroid cells.

Blood Proteins↗