PubMed Health⌕ Search

Biomedical subjects

Gil Tchernia

Publications and source records attributed to Gil Tchernia.

At least 19 recordsLinked to original sources
PubMed2006

Ribosomal protein S24 gene is mutated in Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a rare congenital red-cell aplasia characterized by anemia, bone-marrow erythroblastopenia, and congenital anomalies and is associated with heterozygous mutations in the ribosomal protein (RP) S19 gene (RPS19) in approximately 25% of probands. We report identification of de novo nonsense and splice-site mutations in another RP, RPS24 (encoded by RPS24 [10q22-q23]) in approximately 2% of RPS19 mutation-negative probands. This finding strongly suggests that DBA is a disorder of ribosome synthesis and that mutations in other RP or associated genes that lead to disrupted ribosomal biogenesis and/or function may also cause DBA.

Alternative Splicing↗
PubMed2006

Impaired ribosome biogenesis in Diamond-Blackfan anemia.

The gene encoding the ribosomal protein S19 (RPS19) is frequently mutated in Diamond-Blackfan anemia (DBA), a congenital erythroblastopenia. The consequence of these mutations on the onset of the disease remains obscure. Here, we show that RPS19 plays an essential role in biogenesis of the 40S small ribosomal subunit in human cells. Knockdown of RPS19 expression by siRNAs impairs 18S rRNA synthesis and formation of 40S subunits and induces apoptosis in HeLa cells. Pre-rRNA processing is altered, which leads to an arrest in the maturation of precursors to the 18S rRNA. Under these conditions, pre-40S particles are not exported to the cytoplasm and accumulate in the nucleoplasm of the cells in perinuclear dots. Consistently, we find that ribosome biogenesis and nucleolar organization is altered in skin fibroblasts from DBA patients bearing mutations in the RPS19 gene. In addition, maturation of the 18S rRNA is also perturbed in cells from a patient bearing no RPS19-related mutation. These results support the hypothesis that DBA is directly related to a defect in ribosome biogenesis and indicate that yet to be discovered DBA-related genes may be involved in the synthesis of the ribosomal subunits.

Anemia, Diamond-Blackfan↗
PubMed2006

High-risk pregnancies in Diamond-Blackfan anemia: a survey of 64 pregnancies from the French and German registries.

We reviewed 64 pregnancies in 26 women with Diamond-Blackfan anemia (DBA) included in the French and German DBA registries. Complications were seen in 42 pregnancies (66%) and included abortion, pre-eclampsia, in utero fetal death, intrauterine growth retardation, retroplacental hematoma, pre-term delivery and fetal malformations. Of the 34 children (53%) born alive, 13 had DBA. No correlations were found between pregnancy outcome and features of either maternal or child DBA. Pregnancies in DBA-affected women are at high risk, especially for complications likely to be of vascular-placental origin. Careful monitoring with prevention of severe anemia and early introduction of aspirin is suggested.

Anemia↗
PubMed2006

Two new human DMT1 gene mutations in a patient with microcytic anemia, low ferritinemia, and liver iron overload.

DMT1 mediates the pH-dependent uptake of Fe(2+) from the diet in duodenal enterocytes and in most other cells. It transfers iron from the endosomes to the cytosol following the uptake of the transferrin-transferrin receptor complex. DMT1 mutations are responsible for severe hypochromic microcytic anemia in rodents and in 2 human patients described recently. We report a compound heterozygote for 2 new DMT1 mutations, associated with microcytic anemia from birth and progressive liver iron overload. The first mutation is a GTG deletion in exon 5, leading to the V114 in-frame deletion in transmembrane domain 2, and the second is a G --> T substitution in exon 8 leading to the G212V replacement in transmembrane domain 5. Together with the 2 previously reported cases, this patient defines a new syndrome of congenital microcytic hypochromic anemia, poorly responsive to oral iron treatment, with liver iron overload associated paradoxically with normal to moderately elevated serum ferritin levels.

Amino Acid Sequence↗
PubMed2006

Parvovirus B19-induced anemia in renal transplantation: a role for rHuEPO in resistance to classical treatment.

Human parvovirus B19 (PVB 19) is responsible for pure red cell aplasia in immunocompromised patients, and particularly solid organ recipients. Intravenous immunoglobulins (IVIG) have been shown to be efficient to achieve the correction of anemia in association with the reduction of immunosuppression. We report a case of kidney transplant recipient with PVB 19-induced anemia that did not respond to recombinant human erythropoietin (rHuEPO) and to a first course of IVIG. After discontinuation of rHuEPO, a second course of IVIG was successful with the resolution of anemia. We discuss the role of rHuEPO that may facilitate PVB 19 replication in erythropoietin-sensitive human erythroid progenitor cells.

Drug Resistance↗
PubMed2005

Clinical and laboratory manifestations of congenital dyserythropoietic anemia type I in a cohort of French children.

Congenital dyserythropoietic anemia type I (CDA I) is a rare disorder of erythropoiesis. The objective of this study was to describe the clinical and laboratory manifestations, the diagnosis procedure, the therapeutic approaches and outcome in CDA I. The 12 patients included belong to the retrospective French Multicenter Study. Clinical and biologic data were compiled. Biologic tests included light and, in some cases, electron microscopy, ektacytometry, and red cell membrane protein electrophoresis. Neonatal manifestations (anemia, early jaundice, and/or splenomegaly) and bone abnormalities were present in 11 of the 12 and 6 of the 12 patients, respectively. CDA I was initially misdiagnosed in four children. By the time of diagnosis, anemia with reticulocytosis lower than expected in a hemolytic anemia was present in all patients. Bone marrow electron microscopy examination revealed characteristic findings in all nine children. Red cell membrane protein 4.1 was reduced in all five children. At least one transfusion was required in 11 of the 12 children. Interferon alpha2 corrected anemia in the three children who received monthly transfusions. CDA I is commonly misdiagnosed in children. It should be sought in patients with unexplained chronic anemia, especially when associated with neonatal manifestations, jaundice, splenomegaly, subnormal or low reticulocytosis, and congenital bone malformations.

Adolescent↗
PubMed2005

Clinical and molecular variability in congenital dyserythropoietic anaemia type I.

Congenital dyserythropoietic anaemia (CDA) type I is a rare, inherited disorder characterised by ineffective erythropoiesis and macrocytic anaemia. Complex bone disease has only occasionally been associated with this disease. CDA I is caused by mutations in the CDAN1 gene encoding for codanin-1. Our aim was to characterise the CDAN1 mutation in eight unrelated patients with sporadic CDA I, three of whom had complex bone disease. Six novel mutations in the CDAN1 gene were identified. In two patients, one mutation and in another, both mutations were elusive. No patient was homozygous for a null-type mutation. However, one patient with complex bone disease was homozygous for a splice-site mutation (IVS-12+5G>A). Western blotting revealed that codanin-1 synthesis was 65% less than the control. Five single nucleotide polymorphisms (SNPs) previously unreported in the literature or the SNP database were also identified. Although the absence of codanin-1 is probably lethal, the presence of 35% of the protein was compatible with life but was associated with severe clinical manifestations. However, in most patients studied, no correlation could be established between the expected levels of codanin-1 or the nature of the mutation and the severity of the clinical manifestations.

Adolescent↗
PubMed2005

Recurrent V75M mutation within the Wiskott-Aldrich syndrome protein: description of a homozygous female patient.

The Wiskott-Aldrich syndrome is a rare genetic disorder due to mutations in the WAS gene situated on chromosome X. It is comprised of microthrombocytopenia, eczema and immunodeficiency. However, the phenotypical presentation may vary as to the number and intensity of its manifestations. A milder form of Wiskott-Aldrich syndrome is known as the X-linked thrombocytopenia. We independently found eight individual or familial cases with the V75M substitution (9.76%). This high incidence was partly accounted for by the fact that three cases turned out to be related. The V75M mutation is recurrent, however, due to a CpG island. A genuine homozygous female patient was found. She showed microthrombocytopenia and infections to the same degree as her hemizygous father and brother. The WAS protein was decreased in a comparable fashion in the hemizygotes and the homozygote as well. Its amount was about 10% and 15% of normal in platelets and mononucleated white cells, respectively. In all patients was the picture consistent with XLT.

Adult↗
PubMed2005

Efficacy of mycophenolate mofetil in adult refractory auto-immune cytopenias: a single center preliminary study.

UNLABELLED: Treatment of auto-immune cytopenia refractory to front line therapy with intravenous immunoglobulins and steroids is a matter of concern. We assessed the efficacy and safety of mycophenolate mofetil in a prospective open preliminary study. STUDY DESIGN: Adult patients with steroid refractory auto-immune cytopenias were included. Mycophenolate mofetil (MMF) was added to treatment given at the time of inclusion, and efficacy was evaluated in term of improvement of platelet/haemoglobin levels and in term of reduction of previously given drugs, if any. All auto-immune thrombocytopenic purpura (AITP) patients had serologic assessment for associated auto-antibodies at the time of inclusion. Cytopenias associated with other auto-immune diseases, lymphoproliferative diseases or HIV infection were excluded. RESULTS: From November 1999 through November 2003, 13 patients were included (nine AITP, three auto-immune haemolytic anaemia (AIHA), one Evans' syndrome; four males, nine females; age: 35-72 yr). For AITP patients, an overall response of 78% was observed. Retrospective analysis showed no significant difference between patients having a short disease duration (<1 yr) and longer disease duration; between patients who previously received more or less than three treatments; and between patients for whom MMF was started as monotherapy or in association with prednisone, However, all AITP patients presenting associated auto-antibodies responded to MMF, while only 50% of patients without associated antibodies were responders. All patients presenting AIHA and Evans' syndrome were responders. The drug was well tolerated, with no significant side effects reported. The cumulative data suggest a potential place for MMF in the treatment arsenal of refractory cytopenias.

Adult↗
PubMed2004

Genetic complementation reveals a novel human congenital disorder of glycosylation of type II, due to inactivation of the Golgi CMP-sialic acid transporter.

We have identified a homozygous G>A substitution in the donor splice site of intron 6 (IVS6 + 1G>A) of the cytidine monophosphate (CMP)-sialic acid transporter gene of Lec2 cells as the mutation responsible for their asialo phenotype. These cells were used in complementation studies to test the activity of the 2 CMP-sialic acid transporter cDNA alleles of a patient devoid of sialyl-Le(x) expression on polymorphonuclear cells. No complementation was obtained with either of the 2 patient alleles, whereas full restoration of the sialylated phenotype was obtained in the Lec2 cells transfected with the corresponding human wild-type transcript. The inactivation of one patient allele by a double microdeletion inducing a premature stop codon at position 327 and a splice mutation of the other allele inducing a 130-base pair (bp) deletion and a premature stop codon at position 684 are proposed to be the causal defects of this disease. A 4-base insertion in intron 6 was found in the mother and is proposed to be responsible for the splice mutation. We conclude that this defect is a new type of congenital disorder of glycosylation (CDG) of type IIf affecting the transport of CMP-sialic acid into the Golgi apparatus.

Alternative Splicing↗
PubMed2004

Human blood IgM "memory" B cells are circulating splenic marginal zone B cells harboring a prediversified immunoglobulin repertoire.

The human peripheral B-cell compartment displays a large population of immunoglobulin M-positive, immunoglobulin D-positive CD27(+) (IgM(+)IgD(+)CD27(+)) "memory" B cells carrying a mutated immunoglobulin receptor. By means of phenotypic analysis, complementarity-determining region 3 (CDR3) spectratyping during a T-independent response, and gene-expression profiling of the different blood and splenic B-cell subsets, we show here that blood IgM(+)IgD(+)CD27(+) cells correspond to circulating splenic marginal zone B cells. Furthermore, analysis of this peripheral subset in healthy children younger than 2 years shows that these B cells develop and mutate their immunoglobulin receptor during ontogeny, prior to their differentiation into T-independent antigen-responsive cells. It is therefore proposed that these IgM(+)IgD(+)CD27(+) B cells provide the splenic marginal zone with a diversified and protective preimmune repertoire in charge of the responses against encapsulated bacteria.

Adolescent↗
PubMed2004

Nonsense-mediated and nonstop decay of ribosomal protein S19 mRNA in Diamond-Blackfan anemia.

Mutations in the ribosomal protein (RP)S19 gene have been found in about 25% of the cases of Diamond-Blackfan anemia (DBA), a rare congenital hypoplastic anemia that includes variable physical malformations. Various mutations have been identified in the RPS19 gene, but no investigations regarding the effect of these alterations on RPS19 mRNA levels have been performed. It is well established that mutated mRNA containing a premature stop codon (PTC) or lacking a stop codon can be rapidly degraded by specific mechanisms called nonsense mediated decay (NMD) and nonstop decay. To study the involvement of such mechanisms in DBA, we analyzed immortalized lymphoblastoid cells and primary fibroblasts from patients presenting different kinds of mutations in the RPS19 gene, generating allelic deletion, missense, nonsense, and nonstop messengers. We found that RPS19 mRNA levels are decreased in the cells with allelic deletion and, to a variable extent, also in all the cell lines with PTC or nonstop mutations. Further analysis showed that translation inhibition causes a stabilization of the mutated RPS19 mRNA. Our findings indicate that NMD and nonstop decay affect the expression of mutated RPS19 genes; this may help to clarify genotype-phenotype correlations in DBA.

Alleles↗
PubMed2004

Postmortem diagnosis of Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a rare etiology for congenital anemia, but this diagnosis should be considered when aregenerative hypoplastic anemia occurs in infancy. A term infant girl received a red blood cell transfusion at birth for neonatal anemia (hemoglobin 75 g/L) initially attributed to abruptio placentae. There were no additional investigations. Hemoglobin gradually decreased during the first 4 weeks of life, leading to severe anemia and death despite transfusions. A postmortem diagnosis of DBA was made by extraction of DNA collected on blood filter paper showing a deletion in RPS19 gene. Neonatal anemias should be carefully investigated and close follow-up should be performed during the first months of life, even if there is an obvious hemorrhagic etiology.

Anemia, Diamond-Blackfan↗
PubMed2003

Abnormal glycosylation of red cell membrane band 3 in the congenital disorder of glycosylation Ig.

A description is provided of the clinical presentation in an infant of the recently described congenital disorder of glycosylation type Ig, and the changes affecting glycosylation of red cell membrane band 3, the anion exchanger. It has been shown that the condition stems from a homozygous mutation within the human ortholog of yeast ALG12 gene, which encodes a dolichol-P-mannose:Man7GlcNAc2-PP-dolichol alpha,1-6 mannosyltransferase of the endoplasmic reticulum. The clinical phenotype included prominent central and peripheral manifestations in the CNS. Although the infant studied had no anemia, band 3 abnormally separated into two fractions upon electrophoresis. The chemical composition of the glycans of both fractions was analyzed in detail. The fraction with low electrophoretic mobility was moderately hypoglycosylated (by 27%) and its mannose content was normal. The fraction with high electrophoretic mobility was deeply carbohydrate deficient (by 64%) and had 1 mol mannose in excess but only three residues of N-acetylglucosamine. Glycophorin A was hypoglycosylated with respect to O-linked glycans. Glycosphingolipids of red cells were normal. We suggest that the incomplete biosynthesis of the N-linked glycan of band 3 was largely caused by the persistence of the 3-linked mannose residue on the 6-mannose arm of the trimannosyl moiety of the glycoprotein. It is remarkable that the changes recorded in band 3 have no clinical consequences. Band 3 alteration might serve as an additional indicator (some serum N-glycoproteins of hepatic origin are also indicative) of the congenital disorder of glycosylation type Ig.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2003

Nucleolar localization of RPS19 protein in normal cells and mislocalization due to mutations in the nucleolar localization signals in 2 Diamond-Blackfan anemia patients: potential insights into pathophysiology.

Ribosomal protein S19 (RPS19) is frequently mutated in Diamond-Blackfan anemia (DBA), a rare congenital hypoplastic anemia. Recent studies have shown that RPS19 expression decreases during terminal erythroid differentiation. Currently no information is available on the subcellular localization of normal RPS19 and the potential effects of various RPS19 mutations on cellular localization. In the present study, using wild-type and mutant RPS19 cDNA, we explored the subcellular distribution of normal and mutant proteins in a fibroblast cell line (Cos-7 cells). RPS19 was detected primarily in the nucleus, and more specifically in the nucleoli, where RPS19 colocalized with the nucleolar protein nucleolin. Using various N-terminal and C-terminal deletion constructs, we identified 2 nucleolar localization signals (NoSs) in RPS19: the first comprising amino acids Met1 to Arg16 in the NH2-terminus and the second comprising Gly120 to Asn142 in the COOH-terminus. Importantly, 2 mutations identified in DBA patients, Val15Phe and Gly127Gln, each of which localized to 1 of the 2 NoS, failed to localize RPS19 to the nucleolus. In addition to their mislocalization, there was a dramatic decrease in the expression of the 2 mutant proteins compared to the wild type. This decrease in protein expression was specific for the mutant RPS19, since expression of other proteins was normal. The present findings enable us to document the nucleolar localization signals in RPS19 and help define the phenotypic consequences of some mutations in RPS19 in DBA.

Anemia, Diamond-Blackfan↗
PubMed2003

Sub-lethal hydrops as a manifestation of dehydrated hereditary stomatocytosis in two consecutive pregnancies.

Dehydrated hereditary stomatocytosis (DHS) is a rare congenital hemolytic anemia mapping to 16q23-q24. We showed recently that it is part of a pleiotropic syndrome likely to display pseudohyperkalemia and/or different forms of fetal and placental fluid collections. Here, we report a woman with DHS. She had two consecutive pregnancies associated with severe fetal hydrops. Hydrops would probably have been lethal in the absence of appropriate removal of ascites and excess amniotic fluid. In utero exchange transfusion, performed once, was useless, because anemia was not pronounced enough to be the cause of the hydrops. In both newborns, ascites resolved within a week following birth and never recurred. The association of hydrops and hemolytic anemia suggests the possibility of DHS. Symptomatic treatment of the hydrops assists survival until spontaneous resorption occurs.

Adult↗
PubMed2003

Ten novel Diamond-Blackfan anemia mutations and three polymorphisms within the rps19 gene.

INTRODUCTION: A total of 25% of patients presenting with Diamond-Blackfan anemia (DBA) carry mutations in the rps19 gene, which encodes protein RPS19 of the small ribosomal subunit. The other DBA cases carry mutations in other, unknown gene(s). MATERIALS AND METHODS: We searched mutations in 48 DBA families or isolated patients based on PCR of exons of the rps19 gene and automatic sequencing. We also studied three novel intronic polymorphisms in 85 persons (most of the patients and their relatives, when the latter could be investigated). RESULTS: We identified 10 new mutations within the rps19 gene. We found no obvious correlation between the clinical expression and the nature of the mutation. Besides, we found three polymorphisms within the rps19 gene. Polymorphisms a, b and c were (i) a one-base insertion (+c at position +79) in intron 2, (ii) the g-->c substitution at position +89 also in intron 2 and (iii) the g-->a substitution at position +14 in intron 4. Inheritance studies showed that the polymorphisms were transmitted en bloc, thus defining the --- haplotypes (changes absent) and the +++ haplotypes (changes present). The percentages of each haplotype were about 50% in families and isolated persons with DBA, as well as in controls. CONCLUSION: For the 10 novel mutations found in the rps19 gene, there were no obvious genotype-phenotype correlations. The transmission of the polymorphisms was en bloc and the studies did not suggest any clinical correlates at this stage.

Anemia, Diamond-Blackfan↗