Pathologies attribuables à la consommation de coquillages

From a literature survey, a long list of germs and pollutants found in shellfish has been drawn up, which are potential pathogens when eaten. These consist of microbes, which, carried by the effluent from human or animal communities, reach shoreline ponds and oyster production sites. Transmission from faecal material to the eaten seafood is the origin of a variety of clinical conditions: septicaemia, typhoid, viral hepatitis A, neurological syndromes, and gastro-enteritis induced by bacteria, parasites or viruses.Other illnesses are associated with specific agents coming from the water environment: vibrios and toxic seaweeds, whose growth has been affected by nutrients in the untreated, surrounding waters, and depends on climatic and ecological conditions. The treatment of waste water from communities, and the protection of production sites are the sole means of illness prevention, since the case of shellfish, eaten alive and raw, and having been taken directly from the natural production environment, is a paradox in our ⪡hyper-secure⪢ food system.All food intake in the festive season has risks: for these to be acceptable, producers and control mechanisms must work together to reduce them.     

Molecular pathogenesis of human hepatocellular carcinoma

Hepatocarcinogenesis is a slow process during which genomic changes progressively alter the hepatocellular phenotype to produce cellular intermediates that evolve into hepatocellular carcinoma. During the long preneoplastic stage, in which the liver is often the site of chronic hepatitis, cirrhosis, or both, hepatocyte cycling is accelerated by upregulation of mitogenic pathways, in part through epigenetic mechanisms. This leads to the production of monoclonal populations of aberrant and dysplastic hepatocytes that have telomere erosion and telomerase re-expression, sometimes microsatellite instability, and occasionally structural aberrations in genes and chromosomes. Development of dysplastic hepatocytes in foci and nodules and emergence of hepatocellular carcinoma are associated with the accumulation of irreversible structural alterations in genes and chromosomes, but the genomic basis of the malignant phenotype is heterogeneous. The malignant hepatocyte phenotype may be produced by the disruption of a number of genes that function in different regulatory pathways, producing several molecular variants of hepatocellular carcinoma. New strategies should enable these variants to be characterized.     

Fgf10 regulates hepatopancreatic ductal system patterning and differentiation

During organogenesis, the foregut endoderm gives rise to the many different cell types that comprise the hepatopancreatic system, including hepatic, pancreatic and gallbladder cells, as well as the epithelial cells of the hepatopancreatic ductal system that connects these organs together and with the intestine. However, the mechanisms responsible for demarcating ducts versus organs are poorly understood. Here, we show that Fgf10 signaling from the adjacent mesenchyme is responsible for refining the boundaries between the hepatopancreatic duct and organs. In zebrafish fgf10 mutants, the hepatopancreatic ductal epithelium is severely dysmorphic, and cells of the hepatopancreatic ductal system and adjacent intestine misdifferentiate toward hepatic and pancreatic fates. Furthermore, Fgf10 also functions to prevent the differentiation of the proximal pancreas and liver into hepatic and pancreatic cells, respectively. These data shed light onto how the multipotent cells of the foregut endoderm, and subsequently those of the hepatopancreatic duct, are directed toward different organ fates.     

Loss of BBS proteins causes anosmia in humans and defects in olfactory cilia structure and function in the mouse

Defects in cilia are associated with several human disorders, including Kartagener syndrome, polycystic kidney disease, nephronophthisis and hydrocephalus. We proposed that the pleiotropic phenotype of Bardet-Biedl syndrome (BBS), which encompasses retinal degeneration, truncal obesity, renal and limb malformations and developmental delay, is due to dysfunction of basal bodies and cilia. Here we show that individuals with BBS have partial or complete anosmia. To test whether this phenotype is caused by ciliary defects of olfactory sensory neurons, we examined mice with deletions of Bbs1 or Bbs4. Loss of function of either BBS protein affected the olfactory, but not the respiratory, epithelium, causing severe reduction of the ciliated border, disorganization of the dendritic microtubule network and trapping of olfactory ciliary proteins in dendrites and cell bodies. Our data indicate that BBS proteins have a role in the microtubule organization of mammalian ciliated cells and that anosmia might be a useful determinant of other pleiotropic disorders with a suspected ciliary involvement.     

Exome sequencing identifies recurrent somatic RAC1 mutations in melanoma

We characterized the mutational landscape of melanoma, the form of skin cancer with the highest mortality rate, by sequencing the exomes of 147 melanomas. Sun-exposed melanomas had markedly more ultraviolet (UV)-like C>T somatic mutations compared to sun-shielded acral, mucosal and uveal melanomas. Among the newly identified cancer genes was PPP6C, encoding a serine/threonine phosphatase, which harbored mutations that clustered in the active site in 12% of sun-exposed melanomas, exclusively in tumors with mutations in BRAF or NRAS. Notably, we identified a recurrent UV-signature, an activating mutation in RAC1 in 9.2% of sun-exposed melanomas. This activating mutation, the third most frequent in our cohort of sun-exposed melanoma after those of BRAF and NRAS, changes Pro29 to serine (RAC1(P29S)) in the highly conserved switch I domain. Crystal structures, and biochemical and functional studies of RAC1(P29S) showed that the alteration releases the conformational restraint conferred by the conserved proline, causes an increased binding of the protein to downstream effectors, and promotes melanocyte proliferation and migration. These findings raise the possibility that pharmacological inhibition of downstream effectors of RAC1 signaling could be of therapeutic benefit.     

Meiotic arrest and aneuploidy in MLH3-deficient mice

MutL homolog 3 (Mlh3) is a member of a family of proteins conserved during evolution and having dual roles in DNA mismatch repair and meiosis. The pathway in eukaryotes consists of the DNA-binding components, which are the homologs of the bacterial MutS protein (MSH 2 6), and the MutL homologs, which bind to the MutS homologs and are essential for the repair process. Three of the six homologs of MutS that function in these processes, Msh2, Msh3 and Msh6, are involved in the mismatch repair of mutations, frameshifts and replication errors, and two others, Msh4 and Msh5, have specific roles in meiosis. Of the four MutL homologs, Mlh1, Mlh3, Pms1 and Pms2, three are involved in mismatch repair and at least two, Pms2 and Mlh1, are essential for meiotic progression in both yeast and mice. To assess the role of Mlh3 in mammalian meiosis, we have generated and characterized Mlh3(-/-) mice. Here we show that Mlh3(-/-) mice are viable but sterile. Mlh3 is required for Mlh1 binding to meiotic chromosomes and localizes to meiotic chromosomes from the mid pachynema stage of prophase I. Mlh3(-/-) spermatocytes reach metaphase before succumbing to apoptosis, but oocytes fail to complete meiosis I after fertilization. Our results show that Mlh3 has an essential and distinct role in mammalian meiosis.     

Morphogenesis in skin is governed by discrete sets of differentially expressed microRNAs

During embryogenesis, multipotent progenitors within the single-layered surface epithelium differentiate to form the epidermis and its appendages. Here, we show that microRNAs (miRNAs) have an essential role in orchestrating these events. We cloned more than 100 miRNAs from skin and show that epidermis and hair follicles differentially express discrete miRNA families. To explore the functional significance of this finding, we conditionally targeted Dicer1 gene ablation in embryonic skin progenitors. Within the first week after loss of miRNA expression, cell fate specification and differentiation were not markedly impaired, and in the interfollicular epidermis, apoptosis was not markedly increased. Notably, however, developing hair germs evaginate rather than invaginate, thereby perturbing the epidermal organization. Here we characterize miRNAs in skin, the existence of which was hitherto unappreciated, and demonstrate their differential expression and importance in the morphogenesis of epithelial tissues within this vital organ.     

Hermansky-Pudlak syndrome is caused by mutations in HPS4, the human homolog of the mouse light-ear gene

Hermansky-Pudlak syndrome (HPS) is a disorder of organelle biogenesis in which oculocutaneous albinism, bleeding and pulmonary fibrosis result from defects of melanosomes, platelet dense granules and lysosomes. HPS is common in Puerto Rico, where it is caused by mutations in the genes HPS1 and, less often, HPS3 (ref. 8). In contrast, only half of non-Puerto Rican individuals with HPS have mutations in HPS1 (ref. 9), and very few in HPS3 (ref. 10). In the mouse, more than 15 loci manifest mutant phenotypes similar to human HPS, including pale ear (ep), the mouse homolog of HPS1 (refs 13,14). Mouse ep has a phenotype identical to another mutant, light ear (le), which suggests that the human homolog of le is a possible human HPS locus. We have identified and found mutations of the human le homolog, HPS4, in a number of non-Puerto Rican individuals with HPS, establishing HPS4 as an important HPS locus in humans. In addition to their identical phenotypes, le and ep mutant mice have identical abnormalities of melanosomes, and in transfected melanoma cells the HPS4 and HPS1 proteins partially co-localize in vesicles of the cell body. In addition, the HPS1 protein is absent in tissues of le mutant mice. These results suggest that the HPS4 and HPS1 proteins may function in the same pathway of organelle biogenesis.     

The human Rhesus-associated RhAG protein and a kidney homologue promote ammonium transport in yeast

The Rhesus blood-group antigens are defined by a complex association of membrane polypeptides that includes the non-glycosylated Rh proteins (RhD and RhCE) and the RHag glycoprotein, which is strictly required for cell surface expression of these antigens. RhAG and the Rh polypeptides are erythroid-specific transmembrane proteins belonging to the same family (36% identity). Despite their importance in transfusion medicine, the function of RhAG and Rh proteins remains unknown, except that their absence in Rh(null) individuals leads to morphological and functional abnormalities of erythrocytes, known as the Rh-deficiency syndrome. We recently found significant sequence similarity between the Rh family proteins, especially RhAG, and Mep/Amt ammonium transporters. We show here that RhAG and also RhGK, a new human homologue expressed in kidney cells only, function as ammonium transport proteins when expressed in yeast. Both specifically complement the growth defect of a yeast mutant deficient in ammonium uptake. Moreover, ammonium efflux assays and growth tests in the presence of toxic concentrations of the analogue methylammonium indicate that RhAG and RhGK also promote ammonium export. Our results provide the first experimental evidence for a direct role of RhAG and RhGK in ammonium transport. These findings are of high interest, because no specific ammonium transport system has been characterized so far in human.     

Status, sale and patenting of human genetic material: an international survey.

Following a decade of debate, the European Directive on the Legal Protection of Biotechnological Inventions was adopted by the European Parliament and the Council of the European Union on July 6, 1998. The Directive constitutes a legal and social policy landmark in biotechnology, taking an explicit position on the contentious issue of the patentability of higher life forms. It fails, however, to provide definitive statements on the legal status of human genetic material or the possibility of personal financial gain in relation to such material. An overview of the international, regional and national positions (as found in laws and official policy statements) on the status, commodification and patentability of human genetic material indicates that, although the Directive represents a consolidation of opinions, many issues remain unresolved.     

Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure.

Antenatal Bartter syndrome (aBS) comprises a heterogeneous group of autosomal recessive salt-losing nephropathies. Identification of three genes that code for renal transporters and channels as responsible for aBS has resulted in new insights into renal salt handling, diuretic action and blood-pressure regulation. A gene locus of a fourth variant of aBS called BSND, which in contrast to the other forms is associated with sensorineural deafness (SND) and renal failure, has been mapped to chromosome 1p. We report here the identification by positional cloning, in a region not covered by the human genome sequencing projects, of a new gene, BSND, as the cause of BSND. We examined ten families with BSND and detected seven different mutations in BSND that probably result in loss of function. In accordance with the phenotype, BSND is expressed in the thin limb and the thick ascending limb of the loop of Henle in the kidney and in the dark cells of the inner ear. The gene encodes a hitherto unknown protein with two putative transmembrane alpha-helices and thus might function as a regulator for ion-transport proteins involved in aBS, or else as a new transporter or channel itself.     

Susceptibility loci for intracranial aneurysm in European and Japanese populations

Stroke is the world's third leading cause of death. One cause of stroke, intracranial aneurysm, affects approximately 2% of the population and accounts for 500,000 hemorrhagic strokes annually in mid-life (median age 50), most often resulting in death or severe neurological impairment. The pathogenesis of intracranial aneurysm is unknown, and because catastrophic hemorrhage is commonly the first sign of disease, early identification is essential. We carried out a multistage genome-wide association study (GWAS) of Finnish, Dutch and Japanese cohorts including over 2,100 intracranial aneurysm cases and 8,000 controls. Genome-wide genotyping of the European cohorts and replication studies in the Japanese cohort identified common SNPs on chromosomes 2q, 8q and 9p that show significant association with intracranial aneurysm with odds ratios 1.24-1.36. The loci on 2q and 8q are new, whereas the 9p locus was previously found to be associated with arterial diseases, including intracranial aneurysm. Associated SNPs on 8q likely act via SOX17, which is required for formation and maintenance of endothelial cells, suggesting a role in development and repair of the vasculature; CDKN2A at 9p may have a similar role. These findings have implications for the pathophysiology, diagnosis and therapy of intracranial aneurysm.     

Recommendations of the 2006 Human Variome Project meeting

Lists of variations in genomic DNA and their effects have been kept for some time and have been used in diagnostics and research. Although these lists have been carefully gathered and curated, there has been little standardization and coordination, complicating their use. Given the myriad possible variations in the estimated 24,000 genes in the human genome, it would be useful to have standard criteria for databases of variation. Incomplete collection and ascertainment of variants demonstrates a need for a universally accessible system. These and other problems led to the World Heath Organization-cosponsored meeting on June 20-23, 2006 in Melbourne, Australia, which launched the Human Variome Project. This meeting addressed all areas of human genetics relevant to collection of information on variation and its effects. Members of each of eight sessions (the clinic and phenotype, the diagnostic laboratory, the research laboratory, curation and collection, informatics, relevance to the emerging world, integration and federation and funding and sustainability) developed a number of recommendations that were then organized into a total of 96 recommendations to act as a foundation for future work worldwide. Here we summarize the background of the project, the meeting and its recommendations.     

Neuroendocrine dysplasia in mice lacking protein tyrosine phosphatase sigma

Protein tyrosine phosphatase sigma (PTP-sigma, encoded by the Ptprs gene) is a member of the LAR subfamily of receptor-like protein tyrosine phosphatases that is highly expressed during mammalian embryonic development in the germinal cell layer lining the lateral ventricles of the developing brain, dorsal root ganglia, Rathke's pouch, olfactory epithelium, retina and developing lung and heart. On the basis of its expression and homology with the Drosophila melanogasterorthologues DPTP99 and DPTP100A (refs 5,6), which have roles in the targeting of axonal growth cones, we hypothesized that PTP-sigma may also have a modulating function in cell-cell interactions, as well as in axon guidance during mammalian embryogenesis. To investigate its function in vivo, we generated Ptprs-deficient mice. The resulting Ptprs-/-animals display retarded growth, increased neonatal mortality, hyposmia and hypofecundity. Anatomical and histological analyses showed a decrease in overall brain size with a severe depletion of luteinizing hormone-releasing hormone (LHRH)-immunoreactive cells in Ptprs-/- hypothalamus. Ptprs-/- mice have an enlarged intermediate pituitary lobe, but smaller anterior and posterior lobes. These results suggest that tyrosine phosphorylation-dependent signalling pathways regulated by PTP-sigma influence the proliferation and/or adhesiveness of various cell types in the developing hypothalamo-pituitary axis.     

Les hémocultures en 2001

Blood culture is an essential analysis for the diagnosis and the treatment of sepsis. Microorganisms fund in blood cultures can be isolated from community-acquired infections or from hospital infections.In case of sepsis, the physician must give the microbiologist the clinical information, so that the laboratory makes the right choices in term of method, medium and incubation time.Automated blood culture systems have enhanced the laboratory efficiency and the quality of the patient care. However, the lysis- centrifugation Isolator^® system, a conventional method, remains used for the diagnosis of infections due to fastidious bacteria and for the diagnosis of catheter-associated infections. Methods based on the 16S rDNA amplification, using universal primers, could be a convenient tool used for the management of blood culture negative endocarditis, even if their interest remains to be validated.     

Mutations in the gene encoding B, a novel transporter protein, reduce melanin content in medaka

Pigmentation of the skin is of great social, clinical and cosmetic significance. Several genes that, when mutated, give rise to altered coat color in mice have been identified; their analysis has provided some insight into melanogenesis and human pigmentation diseases. Such analyses do not, however, fully inform on the pigmentation of lower vertebrates because mammals have only one kind of chromatophore, the melanocyte. In contrast, the medaka (a small, freshwater teleost) is a suitable model of the lower vertebrates because it has all kinds of chromatophores. The basic molecular genetics of fish are known and approximately 70 spontaneous pigmentation mutants have been isolated. One of these, an orange-red variant, is a homozygote of a well-known and common allele, b, and has been bred for hundreds of years by the Japanese. Here, we report the first successful positional cloning of a medaka gene (AIM1): one that encodes a transporter that mediates melanin synthesis. The protein is predicted to consist of 12 transmembrane domains and is 55% identical to a human EST of unknown function isolated from melanocytes and melanoma cells. We also isolated a highly homologous gene from the mouse, indicating a conserved function of vertebrate melanogenesis. Intriguingly, these proteins have sequence and structural similarities to plant sucrose transporters, suggesting a relevance of sucrose in melanin synthesis. Analysis of AIM1 orthologs should provide new insights into the regulation of melanogenesis in both teleosts and mammals.     

Évaluation comparée des analyseurs dimension RXL® et Cobas® Intégra 700

The Dimension RXL^® and Cobas^® Integra 700 analysers are multi-parameter biochemical auto-analysers which can be considered to fall within the same range of instrument in view of their analytical possibilities (number and variety of in line tests available) and their theoretical throughput, ranging between 600 and 800 tests per hour, depending on whether or not an ionogram is included. These auto-analysers are well suited to emergency services and to biochemical laboratories with a medium volume of activity. The purpose of this paper is to compare the technical performance of these two analysers for a limited number of analytes, the determination of which occasionally gives rise to difficulties. The assessment made concerns only plasma and urine ionograms, catalytic activity of LDHs, C reactive protein (CRP), calcaemia, serum iron, vancomycinaemia, creatinine in plasma and urine, proteinuria and determination of benzodiazepines in urine. The recommendations of the technical validation protocol (Valtec) published by the Société française de biologie clinique (French clinical biology society) were strictly followed throughout this study. For the Cobas^® Integra 700 analyser, the results obtained show essentially a certain weakness on the urine ionogram. This weakness is reflected in imprecise chloride readings and inexact sodium, potassium and chloride values with respect to the chosen comparison techniques. As far as Dimension RXL^® is concerned, this analyser proved to give imprecise results for urine benzodiazepines as well as inexact CRP readings. For the other analytes, the degree of imprecision is acceptable and the transferability of patients results between the two auto-analysers is possible. In addition, the visible interference thresholds (haemolysis, turbidity and bilirubin) are generally-speaking lower on the Dimension RXL^®. Finally, both analysers are easy to use and the Cobas^® Integra 700 works station proves to be very user-friendly.     

The gamete fusion process is defective in eggs of Cd9-deficient mice

The cell-surface molecule Cd9, a member of the transmembrane-4 superfamily, interacts with the integrin family and other membrane proteins. and is postulated to participate in cell migration and adhesion. Expression of Cd9 enhances membrane fusion between muscle cells and promotes viral infection in some cells. Fertilization also involves membrane fusion, between gametes. In mammals, the sperm binds to microvilli on the egg surface, and sperm-egg membrane fusion first occurs around the equatorial region of the sperm head12. The fused membrane is then disrupted, and the sperm nucleus as well as the cytoplasm is incorporated into the egg. Cd9 is expressed on the plasma membrane of the mouse egg, and an anti-Cd9 monoclonal antibody inhibits sperm-egg surface interactions. We generated Cd9 mice and found that homozygous mutant females were infertile. Sperm-egg binding was normal, but sperm-egg fusion was almost entirely inhibited in eggs from Cd9 females. Intracellular Ca2 oscillations, which signal fertilization, were absent in almost all mutant eggs; in rare cases, a response occurred after a long time period. In normal animals, Cd9 molecules were expressed on the egg microvilli and became densely concentrated at the sperm attachment site. Thus, our results show that Cd9 is important in the gamete fusion process at fertilization.     

Mutations in MYH9 result in the May-Hegglin anomaly, and Fechtner and Sebastian syndromes. The May-Heggllin/Fechtner Syndrome Consortium

The autosomal dominant, giant-platelet disorders, May-Hegglin anomaly (MHA; MIM 155100), Fechtner syndrome (FTNS; MIM 153640) and Sebastian syndrome (SBS), share the triad of thrombocytopenia, large platelets and characteristic leukocyte inclusions ('D?hle-like' bodies). MHA and SBS can be differentiated by subtle ultrastructural leukocyte inclusion features, whereas FTNS is distinguished by the additional Alport-like clinical features of sensorineural deafness, cataracts and nephritis. The similarities between these platelet disorders and our recent refinement of the MHA (ref. 6) and FTNS (ref. 7) disease loci to an overlapping region of 480 kb on chromosome 22 suggested that all three disorders are allelic. Among the identified candidate genes is the gene encoding nonmuscle myosin heavy chain 9 (MYH9; refs 8-10), which is expressed in platelets and upregulated during granulocyte differentiation. We identified six MYH9 mutations (one nonsense and five missense) in seven unrelated probands from MHA, SBS and FTNS families. On the basis of molecular modelling, the two mutations affecting the myosin head were predicted to impose electrostatic and conformational changes, whereas the truncating mutation deleted the unique carboxy-terminal tailpiece. The remaining missense mutations, all affecting highly conserved coiled-coil domain positions, imparted destabilizing electrostatic and polar changes. Thus, our results suggest that mutations in MYH9 result in three megakaryocyte/platelet/leukocyte syndromes and are important in the pathogenesis of sensorineural deafness, cataracts and nephritis.