- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 1 to 7 of 7 (0.136 seconds)| 1 |
Cytosine methylation, methyltransferases and flowering time in Arabidopsis thalianaGenger, Ruth Kathleen, Ruth.Genger@csiro.au January 2000 (has links)
Environmental signals such as photoperiod and temperature provide plants with seasonal information, allowing them to time flowering to occur in favourable conditions. Most ecotypes of the model plant Arabidopsis thaliana flower earlier in long photoperiods and after prolonged exposure to cold (vernalization). The vernalized state is stable through mitosis, but is not transmitted to progeny, suggesting that the vernalization signal may be transmitted via a modification of DNA such as cytosine methylation. The role of methylation in the vernalization response is investigated in this thesis.
¶
Arabidopsis plants transformed with an antisense construct to the cytosine methyltransferase METI (AMT) showed significant decreases in methylation. AMT plants flowered significantly earlier than unvernalized wildtype plants, and the promotion of flowering correlated with the extent of demethylation. The flowering time of mutants with decreased DNA methylation (ddm1) was promoted only in growth conditions in which wildtype plants showed a vernalization response, suggesting that the early flowering response to demethylation operated specifically through the vernalization pathway.
¶
The AMT construct was crossed into two late flowering mutants that differed in vernalization responsiveness. Demethylation promoted flowering of the vernalization responsive mutant fca, but not of the fe mutant, which has only a slight vernalization response. This supports the hypothesis that demethylation is a step in the vernalization pathway.
¶
The role of gibberellic acid (GA) in the early flowering response to demethylation was investigated by observing the effect of the gai mutation, which disrupts the GA signal transduction pathway, on flowering time in plants with demethylated DNA. The presence of a single gai allele delayed flowering, suggesting that the early flowering response to demethylation requires a functional GA signal transduction pathway, and that demethylation increases GA levels or responses, directly or indirectly.
¶
In most transgenic lines, AMT-mediated demethylation did not fully substitute for vernalization. This indicates that part of the response is not affected by METI-mediated methylation, and may involve a second methyltransferase or a factor other than methylation. A second Arabidopsis methyltransferase, METIIa, was characterized and compared to METI. The two genes are very similar throughout the coding region, and share the location of their eleven introns, indicating that they diverged relatively recently. Both are transcribed in all tissues and at all developmental stages assayed, but the level of expression of METI is significantly higher than that of METIIa. The possible functions of METI, METIIa, and other Arabidopsis cytosine methyltransferase genes recently identified are discussed.
|
| 2 |
Epigenetická regulace genů HLA asociovaných s celiakií / Epigenetic regulation of HLA genes asociated with celiac diseaseHudec, Michael January 2017 (has links)
Introduction: HLA class II system presents one of the most important mechanism in immune system, which is able to recognise pathogens and damaged cells. Some HLA class II alleles are associated with autoimmune diseases, for example celiac disease, which is typical by chronic inflammation of small intestine and other following symptoms. The risk HLA class II variants are DQ2 and DQ8. Epigenetic mechanisms that regulates gene expression, especially methylation of cytosine in promoter region of DQ2 and/or DQ8 alleles, could have influence on development of T lymphocytes in the thymus, where T-lymphocytes develop and pass a few stages in, and only the survival clones can be part of function immune system. Aim: The aim of this study is to compare methylation level of promoter regions of HLA DQ2 and DQ8 alleles between celiac patients and healthy controls. Another goal is to compare expression level of DQ2 and DQ8 variants between these two groups. Methods: DNA and RNA were isolated from full blood of two sets of donors. DNA was converted by bisulphite conversion and then amplified by Nested PCR. The PCR product was cloned to bacteria. Than positive colonies were selected. Subsequent methylation analysis was performed. RNA was converted to cDNA by Reverse transcription. Relative expression was analyzed...
|
| 3 |
Genome-wide nucleosome map and cytosine methylation levels of an ancient human genome.Pedersen, J.S., Valen, E., Velazquez, A.M.V., Parker, B.J., Lindgreen, S., Lilje, B., Tobin, Desmond J., Kelly, T.K., Vang, S., Andersson, R., Jones, P.A., Hoover, C.A., Prokhortchouk, E., Rubin, E.M., Sandelin, A., Gilbert, M.T.P., Krogh, A., Willerslev, E. January 2014 (has links)
yes / Epigenetic information is available from contemporary organisms, but is difficult to track back in evolutionary time.
Here, we show that genome-wide epigenetic information can be gathered directly from next-generation sequence reads of
DNA isolated from ancient remains. Using the genome sequence data generated from hair shafts of a 4000-yr-old Paleo-
Eskimo belonging to the Saqqaq culture, we generate the first ancient nucleosome map coupled with a genome-wide
survey of cytosine methylation levels. The validity of both nucleosome map and methylation levels were confirmed by the
recovery of the expected signals at promoter regions, exon/intron boundaries, and CTCF sites. The top-scoring nucleosome
calls revealed distinct DNA positioning biases, attesting to nucleotide-level accuracy. The ancient methylation
levels exhibited high conservation over time, clustering closely with modern hair tissues. Using ancient methylation
information, we estimated the age at death of the Saqqaq individual and illustrate how epigenetic information can be used
to infer ancient gene expression. Similar epigenetic signatures were found in other fossil material, such as 110,000- to
130,000-yr-old bones, supporting the contention that ancient epigenomic information can be reconstructed from a deep
past. Our findings lay the foundation for extracting epigenomic information from ancient samples, allowing shifts in
epialleles to be tracked through evolutionary time, as well as providing an original window into modern epigenomics.
|
| 4 |
Genome-Wide Regulation of Both Canonical and Non-canonical RNA-directed DNA Methylation Mechanisms in <i>Arabidopsis thaliana</i>Panda, Kaushik Kant January 2017 (has links)
No description available.
|
| 5 |
Structure-function analysis of CXXC finger protein 1Tate, Courtney Marie 26 January 2010 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This dissertation describes structure-function studies of CXXC finger protein 1 (Cfp1), encoded by the CXXC1 gene, in order to determine the functional significance of Cfp1 protein domains and properties. Cfp1 is an important regulator of chromatin structure and is essential for mammalian development. Murine embryonic stem (ES) cells lacking Cfp1 (CXXC1-/-) are viable but demonstrate a variety of defects, including hypersensitivity to DNA damaging agents, reduced plating efficiency and growth, decreased global and gene-specific cytosine methylation, failure to achieve in vitro differentiation, aberrant histone methylation, and subnuclear mis-localization of Setd1A, the catalytic component of a histone H3K4 methyltransferase complex, and tri-methylated histone H3K4 (H3K4me3) with regions of heterochromatin. Expression of wild-type Cfp1 in CXXC1-/- ES cells rescues the observed defects, thereby providing a convenient method to assess structure-function relationships of Cfp1. Cfp1 cDNA expression constructs were stably transfected into CXXC1-/- ES cells to evaluate the ability of various Cfp1 fragments and mutations to rescue the CXXC1-/- ES cell phenotype.
These experiments revealed that expression of either the amino half of Cfp1 (amino acids 1-367) or the carboxyl half of Cfp1 (amino acids 361-656) is sufficient to rescue the hypersensitivity to DNA damaging agents, plating efficiency, cytosine and histone methylation, and differentiation defects. These results reveal that Cfp1 contains redundant functional domains for appropriate regulation of cytosine methylation, histone methylation, and in vitro differentiation. Additional studies revealed that a point mutation (C169A) that abolishes DNA-binding activity of Cfp1 ablates the rescue activity of the 1-367 fragment, and a point mutation (C375A) that abolishes the interaction of Cfp1 with the Setd1A and Setd1B histone H3K4 methyltransferase complexes ablates the rescue activity of the 361-656 Cfp1 fragment. In addition, introduction of both point mutations (C169A and C375A) ablates the rescue activity of the full-length Cfp1 protein. These results indicate that retention of either DNA-binding or Setd1 association of Cfp1 is required to rescue hypersensitivity to DNA damaging agents, plating efficiency, cytosine and histone methylation, and in vitro differentiation. In contrast, confocal immunofluorescence analysis revealed that full-length Cfp1 is required to restrict Setd1A and histone H3K4me3 to euchromatic regions.
|
| 6 |
A Novel Approach to Identify Candidate Imprinted Genes in HumansShapiro, Jonathan 21 March 2012 (has links)
Many imprinted genes are necessary for normal human development. Approximately 70 imprinted genes have been identified in humans. I developed a novel approach to identify candidate imprinted genes in humans using the premise that imprinted genes are often associated with nearby parent-of-origin-specific DNA differentially methylated regions (DMRs). I identified parent-of-origin-specific DMRs using sodium bisulfite-based DNA (CpG) methylation profiling of uniparental tissues, mature cystic ovarian teratoma (MCT) and androgenetic complete hydatidiform mole (AnCHM), and biparental tissues, blood and placenta. In support of this approach, the CpG methylation profiling led to the identification of parent-of-origin-specific differentially methylated CpG sites (DMCpGs) in known parent-of-origin-specific DMRs. I found new DMRs for known imprinted genes NAP1L5 and ZNF597. Most importantly, I discovered many new DMCpGs, which were associated with nearby genes, i.e., candidate imprinted genes. Allelic expression analyses of one candidate imprinted gene, AXL, suggested polymorphic imprinting of AXL in human blood.
|
| 7 |
A Novel Approach to Identify Candidate Imprinted Genes in HumansShapiro, Jonathan 21 March 2012 (has links)
Many imprinted genes are necessary for normal human development. Approximately 70 imprinted genes have been identified in humans. I developed a novel approach to identify candidate imprinted genes in humans using the premise that imprinted genes are often associated with nearby parent-of-origin-specific DNA differentially methylated regions (DMRs). I identified parent-of-origin-specific DMRs using sodium bisulfite-based DNA (CpG) methylation profiling of uniparental tissues, mature cystic ovarian teratoma (MCT) and androgenetic complete hydatidiform mole (AnCHM), and biparental tissues, blood and placenta. In support of this approach, the CpG methylation profiling led to the identification of parent-of-origin-specific differentially methylated CpG sites (DMCpGs) in known parent-of-origin-specific DMRs. I found new DMRs for known imprinted genes NAP1L5 and ZNF597. Most importantly, I discovered many new DMCpGs, which were associated with nearby genes, i.e., candidate imprinted genes. Allelic expression analyses of one candidate imprinted gene, AXL, suggested polymorphic imprinting of AXL in human blood.
|
Page generated in 0.5286 seconds