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Genes Characteristic (gene + characteristic)
Selected AbstractsA new multimarker test for family-based association studiesGENETIC EPIDEMIOLOGY, Issue 1 2007Cyril S. Rakovski Abstract We propose a new multimarker test for family-based studies in candidate genes. We use simulations under different genetic models to assess the performance of competing testing strategies, characterized in this study as combinations of the following important factors: genes, statistical tests, tag single nucleotide polymorphisms (SNP) methods, number of tag SNPs and family designs. An ANOVA model is employed to provide descriptive summaries of the effects on power of the above-mentioned factors. We find that tag SNP methods, gene characteristics and family designs have minimal impact on the best testing strategy. The familywise error rate (FWER) controlling multiple comparison procedure and the new multimarker test offer the highest power followed by the asymptotic global haplotype test. Both the FWER and the multimarker test are invariant to family designs and gain power as we increase the number of tag SNPs. However, the performance of the global haplotype test is slightly degraded when analyzing larger numbers of tag SNPs. Within the framework of our study, the best strategy for family-based studies in candidate genes that emerged from our analysis is to use the FWER or the multimarker test and select 6,10 tag SNPs using any of the tag SNP methods considered. We confirm the conclusions of our study with an application to Alzheimer's disease data. Genet. Epidemiol. © 2006 Wiley-Liss, Inc. [source] Stem cell generation and choice of fate: role of cytokines and cellular microenvironmentJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2000S.N. Constantinescu Hematopoietic stem cells (HSC) have provided a model for the isolation, enrichment and transplantation of stem cells. Gene targeting studies in mice have shown that expression of the thrombopoietin receptor (TpoR) is linked to the accumulation of HSCs capable to generate long-term blood repopulation when injected into irradiated mice. The powerful increase in vivo in HSC numbers by retrovirally transduced HOX4B, a homeotic gene, along with the role of the TpoR, suggested that stem cell fate, renewal, differentiation and number can be controlled. The discovery of the precise region of the mouse embryo where HSCs originate and the isolation of supporting stromal cell lines open the possibility of identifying the precise signals required for HSC choice of fate. The completion of human genome sequencing coupled with advances in gene expression profiling using DNA microarrays will enable the identification of key genes deciding the fate of stem cells. Downstream from HSCs, multipotent hematopoietic progenitor cells appear to co-express a multiplicity of genes characteristic of different blood lineages. Genomic approaches will permit the identification of the select group of genes consolidated by the commitment of these multipotent progenitors towards one or the other of the blood lineages. Studies with neural stem cells pointed to the unexpected plastic nature of these cells. Isolation of stem cells from multiple tissues may suggest that, providing the appropriate environment/signal, tissues could be regenerated in the laboratory and used for transplantation. A spectacular example of influence of the environment on cell fate was revealed decades ago by using mouse embryonic stem cells (ES). Injected into blastocysts, ES cells contribute to the formation of all adult tissues. Injected into adult mice, ES cells become cancer cells. After multiple passages as ascites, when injected back into the blastocyst environment, ES- derived cancer cells behaved again as ES cells. More recently, the successful cloning of mammals and reprogramming of transferred nuclei by factors in the cytoplasm of oocytes turned back the clock by showing that differentiated nuclei can be "re-booted" to generate again the stem cells for different tissues. [source] Studies on diarrheagenic Escherichia coli isolated from children with diarrhea in MyanmarMICROBIOLOGY AND IMMUNOLOGY, Issue 1 2008Eizo Takahashi ABSTRACT Escherichia coli isolates from 217 children in Myanmar with diarrhea were investigated for the presence of virulence genes related to diarrhea by colony hybridization and PCR. The genes examined were lt, stI, stII, stx1, stx2, eae, bfp, pCVD (which is the representative gene of plasmid of pCVD of EAEC), and ial (which is invasion-associated locus of the invasion plasmid found in EIEC). Isolates from 47 of 217 children (21.7%) possessed virulence genes characteristic of diarrheagenic E. coli. No instance was found of co-existence of different E. coli strains with different virulence genes in the same patient. Diarrheagenic E. coli are currently classified into five categories based on their virulence markers: ETEC, EHEC, EPEC, EAEC, and EIEC. Of the 47 isolates examined, 30 were EAEC, 12 were EPEC and 5 were ETEC. Susceptibility tests for antimicrobial agents showed that almost all diarrheagenic isolates were resistant to penicillin, tetracycline and streptomycin. However, the majority of strains were sensitive to cephalexin, nalidixic acid and norfloxacin. In particular, 42 of the 47 isolates were sensitive to norfloxacin, which is a fluoroquinolone. This study shows EAEC and EPEC are responsible for sporadic diarrhea in Myanmar and fluoroquinolones appear to be effective in the treatment of these patients. [source] A method for fast and simple detection of major diarrhoeagenic Escherichia coli in the routine diagnostic laboratoryCLINICAL MICROBIOLOGY AND INFECTION, Issue 5 2007S. Persson Abstract A multiplex PCR was developed for the detection of the following genes characteristic of diarrhoeagenic Escherichia coli (DEC): verocytotoxins 1 (vtx1) and 2 (vtx2), characteristic of verocytotoxin-producing E. coli (VTEC); intimin (eae), found in enteropathogenic E. coli (EPEC), attaching and effacing E. coli and VTEC; heat-stable enterotoxin (estA) and heat-labile enterotoxin (eltA), characteristic of enterotoxigenic E. coli (ETEC); and invasive plasmid antigen (ipaH), characteristic of enteroinvasive E. coli (EIEC) and Shigella spp. The method allowed the simultaneous identification of all six genes in one reaction, and included a 16S rDNA internal PCR control. When applied to pure cultures from a reference strain collection, all virulence genes in 124 different DEC strains and 15 Shigella spp. were identified correctly, and there were no cross-reactions with 13 non- E. coli species. The detection limit of the method was 102,103 DEC CFU/PCR in the presence of 106 non-target cells. When the multiplex PCR was tested with colonies from plate cultures of clinical stool samples, it was a faster, more sensitive, less expensive and less laborious diagnostic procedure than DNA hybridisation. When used with DNA purified from spiked stool samples (by two different commercial kits), the method had a detection limit of 106 CFU/mL stool sample. [source] | |||||||||||||