Project description:comparative genomic hybridization between Burkholderia cepacia sequenced strains to determine what are the limits to strain relativity in order to still provide accurate estimations of gene content
Project description:To examine the ways in which gene expression varies in natural populations and its relationship to genetic divergence, we estimated allele-specific expression in the offspring of multiple wild C. elegans strains crossed with the laboratory reference strain N2. Allele-specific expression analyses are uniquely sensitively able to identify cis regulatory changes, and coupled with analyses of differential expression between parental strains and parents and offspring can determine the regulatory pattern and inheritance mode of gene expression across the genome. We chose 7 strains that represented a range of divergence from N2 and spanned the species tree to cross with N2: EG4348; DL238; CB4856 (the classical ‘Hawaiian’ strain); ECA722; QX1211; and ECA701 and XZ1516 (two extremely diverged strains). This study sheds light on the relationship of genetic and expression divergence, the global patterns of inheritance and regulatory mode of genes in C. elegans, and the factors that differentiate genes with expression divergence from those with stabler expression.
Project description:This SuperSeries is composed of the following subset Series: GSE34280: Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Affymetrix SNP6 Arrays] GSE34355: Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Illumina Infinium HumanMethylation27 Beadchip v1.2] Refer to individual Series
Project description:DNA oligonucleotide microarrays (oligoarrays) are being developed continuously; however, several issues regarding the applicability of these arrays for whole-genome DNA-DNA strain comparisons (genomotyping) have not been investigated. For example, the extent of false negatives (i.e., no hybridization signal is observed when the amino acid sequence is conserved but the nucleotide sequence has diverged to a level that does not allow hybridization) remains speculative. To provide quantitative answers to such questions, we performed competitive DNA-DNA oligoarray (60-mer) hybridizations with several fully sequenced (tester) strains and a reference strain (whose genome was used to design the oligoarray probes) of the genus Burkholderia and compared the experimental results obtained to the results predicted based on bioinformatic modeling of the probe-target pair using the available sequences. Our comparisons revealed that the fraction of the total probes that provided experimental results consistent with the predicted results decreased substantially with increasing divergence of the tester strain from the reference strain. The fractions were 90.8%, 84.3%, and 77.4% for tester strains showing 96% 89%, and 80% genome-aggregate average nucleotide identity (ANI) to the reference strain, respectively. New approaches to determine gene presence or absence based on the hybridization signal, which outperformed previous approaches (e.g., 92.9% accuracy versus 86.0% accuracy) and to normalize across different array experiments are also described. Collectively, our results suggest that the performance of oligoarrays is acceptable for tester strains showing >90% ANI to the reference strain and provide useful guidelines for using oligoarray applications in environmental gene detection and gene expression studies with strains other than the reference strain.
Project description:Little is known about the extent of genetic variability among Entamoeba strains and potential genotypic associations with virulence. Variable phenotypes have been identified for Entamoeba strains. E. histolytica is invasive and causes colitis and liver abscesses, but only in 10% of infected individuals; 90% of subjects remain asymptomatically colonized. E. dispar, a closely related species, appears to be incapable of causing invasive disease. In order to determine the extent of genetic diversity among Entamoeba strains we have developed an E. histolytica genomic DNA microarray and used it to genotype strains of E. dispar and E. histolytica. Based on the identification of divergent genetic loci, all six strains (four EH and two ED) had unique genetic fingerprints. Genomic regions with unusually high levels of divergence were identified indicating that structural or evolutionary pressures are molding selective regions of the Entamoeba genome. Comparison of divergent genetic regions allowed us to readily distinguish between EH and ED, identify novel genetic regions that may be used for strain and species typing, and identity a number of novel potential virulence determinants. Among these are Androgen Inducible Gene1, a CXXC receptor kinase, a peroxiredoxin 1-related gene, a Ras family member gene, a Rab geranylgeranyltransferase, and a gene with a UPF0034 domain. Among the four EH strains, an avirulent strain EH (Rahman) was the most divergent and phylogenetically distinct raising the intriguing possibility that genetic subtypes of E. histolytica may be at least partially responsible for the observed variability in clinical outcomes. Our approach shows the utility of a microarray-based genotyping assay to identify genetic variability between Entamoeba isolates and can readily be applied to the study of clinical isolates. A genotyping experiment design type classifies an individual or group of individuals on the basis of alleles, haplotypes, SNP's. Keywords: genotyping_design
Project description:The interplay between phenotypic plasticity and adaptive evolution has long been an important topic of evolutionary biology. This process is critical to our understanding of a species evolutionary potential in light of rapid climate changes. Despite recent theoretical work, empirical studies of natural populations, especially in marine invertebrates, are scarce. In this study, we investigated the relationship between adaptive divergence and plasticity by integrating genetic and phenotypic variation in Pacific oysters from its natural range in China. Genome resequencing of 371 oysters revealed unexpected fine-scale genetic structure that is largely consistent with phenotypic divergence in growth, physiology, thermal tolerance and gene expression across environmental gradient. These findings suggest that selection and local adaptation are pervasive and together with limited gene flow shape adaptive divergence. Plasticity in gene expression is positively correlated with evolved divergence, indicating that plasticity is adaptive and likely favored by selection in organisms facing dynamic environments such as oysters. Divergence in heat response and tolerance implies that the evolutionary potential to a warming climate differs among oyster populations. We suggest that trade-offs in energy allocation are important to adaptive divergence with acetylation playing a role in energy depression under thermal stress.
Project description:Little is known about the extent of genetic variability among Entamoeba strains and potential genotypic associations with virulence. Variable phenotypes have been identified for Entamoeba strains. E. histolytica is invasive and causes colitis and liver abscesses, but only in 10% of infected individuals; 90% of subjects remain asymptomatically colonized. E. dispar, a closely related species, appears to be incapable of causing invasive disease. In order to determine the extent of genetic diversity among Entamoeba strains we have developed an E. histolytica genomic DNA microarray and used it to genotype strains of E. dispar and E. histolytica. Based on the identification of divergent genetic loci, all six strains (four EH and two ED) had unique genetic fingerprints. Genomic regions with unusually high levels of divergence were identified indicating that structural or evolutionary pressures are molding selective regions of the Entamoeba genome. Comparison of divergent genetic regions allowed us to readily distinguish between EH and ED, identify novel genetic regions that may be used for strain and species typing, and identity a number of novel potential virulence determinants. Among these are Androgen Inducible Gene1, a CXXC receptor kinase, a peroxiredoxin 1-related gene, a Ras family member gene, a Rab geranylgeranyltransferase, and a gene with a UPF0034 domain. Among the four EH strains, an avirulent strain EH (Rahman) was the most divergent and phylogenetically distinct raising the intriguing possibility that genetic subtypes of E. histolytica may be at least partially responsible for the observed variability in clinical outcomes. Our approach shows the utility of a microarray-based genotyping assay to identify genetic variability between Entamoeba isolates and can readily be applied to the study of clinical isolates. A genotyping experiment design type classifies an individual or group of individuals on the basis of alleles, haplotypes, SNP's. User Defined
Project description:The aim of this experiment is to test how atypical codon assignment (in our case Ser and Leu at CUG sites) flexibility can provide an effective mechanism to alter the genetic code. We have reengineered C. albicans strains to mis-incorporate increasing levels of Leu at protein CUG sites.