Project description:Methods: mRNA profiles of untransfected HeLa cells (wild-type; wt) were compared with mRNA profiles of HeLa cells stably maintaining an S/MAR-based episome. Results: We here report for the first time that episomally maintained S/MAR-based vectors do not alter gene expression profile of the host cell's genome. No global changes in gene expression in episome maintaining cells, compared to non-transfected cells could be observed. To identify differentially expressed genes, false discovery rate (FDR; q-value) cut off was set to 0.01. Significantly differentially expressed genes with q<0.01 and an absolute fold-change of 2 were not detected. For verification, we chose five genes with high fold-change and low q-values (q<0.05) and compared expression levels between untransfected HeLa and HeLa stably maintaining an S/MAR-based within three replicates in qPCR. Conclusions: S/MAR-based replicons used in this study do not code for viral proteins but tend to co-localise with promoter sequences and transcription start sites. Recent observations that cooperatively transcribed promoters can influence each other raise concerns that S/MAR-based replicons have the potential to alter endogenous gene expression. Therefore, we compared the transcriptome of untransfected HeLa cells with HeLa cells stably maintaining an S/MAR-based episome. Setting the FDR to <0.01, we found no significantly differentially expressed genes. This finding is of utmost importance for potential gene therapeutic application of S/MAR-based replicons.
Project description:Methods: Autonomously replicating vectors represent a simple and versatile model system for genetic modifications, but their localisation in the nucleus is largely unknown. Using circular chromosome conformation capture we mapped genomic contact sites of S/MAR-based replicons in HeLa cells. The influence of cis-active sequences on genomic localisation was assessed using replicons containing either an insulator sequence or an intron Results: While the original and the insulator-containing replicons displayed distinct contact sites, the intron-containing replicon showed a rather broad genomic contact pattern. Our results indicate a preference for certain chromatin structures and a rather non-dynamic behaviour during mitosis. Independent of inserted cis-active elements established vector molecules reside preferentially within actively transcribed regions, especially within promoter sequences and transcription start sites. Conclusions: S/MAR-based episomal replicons have a limited number of preferential contact sites and seem to be fairly non-dynamic during mitosis. We show that cis-acting elements do have an impact on the chormosomal localisation of episomal replicons, even though the epigenetic signatue of these contact sites are similar. Independently of the inserted cis-acting element, these contact sites are preferentially located within actively transcribed regions, especially promoter sites. Knowledge of preferred contact sites of exogenous DNA, e.g. viral or non-viral episomes, contribute to our understanding of episome behaviour in the nucleus and can be used for vector improvement and guiding of DNA sequences to specific subnuclear sites.
Project description:Analysis of the episomal backbone's influence on gene expression. The first hypothesis tested in the present study is that the episomal EBNA vectors, which rely on the EBNA-1 oncoprotein for episomal maintenance, have a greater influence on the cells' expression profiles than S/MAR vectors. The second hypothesis tested was that when bacterial sequences are removed from the episomal vector backbone, the gene disturbance is minimal.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain.A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development.Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.
Project description:PurposeWe investigated the evidence of recent positive selection in the human phototransduction system at single nucleotide polymorphism (SNP) and gene level.MethodsSNP genotyping data from the International HapMap Project for European, Eastern Asian, and African populations was used to discover differences in haplotype length and allele frequency between these populations. Numeric selection metrics were computed for each SNP and aggregated into gene-level metrics to measure evidence of recent positive selection. The level of recent positive selection in phototransduction genes was evaluated and compared to a set of genes shown previously to be under recent selection, and a set of highly conserved genes as positive and negative controls, respectively.ResultsSix of 20 phototransduction genes evaluated had gene-level selection metrics above the 90th percentile: RGS9, GNB1, RHO, PDE6G, GNAT1, and SLC24A1. The selection signal across these genes was found to be of similar magnitude to the positive control genes and much greater than the negative control genes.ConclusionsThere is evidence for selective pressure in the genes involved in retinal phototransduction, and traces of this selective pressure can be demonstrated using SNP-level and gene-level metrics of allelic variation. We hypothesize that the selective pressure on these genes was related to their role in low light vision and retinal adaptation to ambient light changes. Uncovering the underlying genetics of evolutionary adaptations in phototransduction not only allows greater understanding of vision and visual diseases, but also the development of patient-specific diagnostic and intervention strategies.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.