Roles for the Cdx transcription factors during anteroposterior patterning and development of the posterior embryo have been well described, yet little is known about Cdx functions during mesoderm specification. In the studies presented here, novel roles for Cdx during gastrulation are presented. In the first of two studies, the role of Cdx factors during cardiac mesoderm specification is investigated. We demonstrate that Cdx factors epigenetically restrict cardiac progenitor specification, preventing the ectopic expression of cardiogenic genes within progenitor mesodermal populations. We provide evidence to suggest that this occurs through interaction with Brg1, a subunit of the SWI/SNF chromatin remodeling complex, and propose a molecular mechanism by which Cdx-mediated recruitment of the SWI/SNF complex is required to maintain repression of cardiac targets at developmental stages where Cdx transcription factors are no longer expressed. Following this, Cdx-dependent gene expression programs were identified in the extra-embryonic yolk sac. RNA-sequencing of Cdx-mutant yolk sacs revealed novel Cdx-dependent gene targets involved in ion and nutrient transport, functions analogous to those previously described for Cdx in the adult intestinal epithelium. Subsequent experimentation revealed that, for a subset of these targets, regulation correlates with the maintenance of H3K27me3 marks. Finally, we provide evidence to suggest Cdx-dependent H3K27me3 marks are established at early developmental stages, when yolk sac progenitors are specified from the streak. Together, these studies describe novel roles for Cdx factors in mesoderm specification during gastrulation, and evoke molecular mechanisms by which Cdx might program early mesodermal populations for gene expression at later developmental stages through interactions with epigenetic regulatory complexes.

Indiana University-Purdue University Indianapolis (IUPUI) / Myelodysplastic syndrome (MDS) is a clonal disease arising from mutated hematopoietic stem cells (HSCs). MDS stem cells originate from pre-leukemic HSCs, which have enhanced competitive advantage over wild-type (WT) HSCs but normal differentiation capacity. Recently, acquired somatic gain-of-function (GOF) TP53 mutations were identified in the blood of aged healthy individuals as well as in patients with MDS. However, the role of GOF TP53 mutations in clonal hematopoiesis and the pathogenesis of MDS is largely unknown. Based upon our previous studies and clinical findings, I hypothesized that GOF mutant p53 drives the development of pre-leukemic HSCs with enhanced competitive advantage, leading to clonal expansion and the pathogenesis of MDS. To test my hypothesis, I examined HSC behaviors in young p53+/+ and p53R248W/+ mice. I discovered that p53R248W enhances the repopulating potential of HSCs without affecting terminal differentiation. I also found that GOF mutant p53 protects HSCs from genotoxic stress and promotes their expansion. To investigate the role of mutant p53 in the pathogenesis of hematological malignancies, I monitored disease development in p53+/+ and p53R248W/+ mice and observed that some mutant p53 mice develop MDS during aging. Therefore, I demonstrated that GOF mutant p53 enhances the repopulating potential of HSCs and drives the development of pre-leukemic HSCs, predisposing aged mutant p53 mice to MDS development. Mechanistically, I found that mutant p53 increases the chromatin accessibility to genes important for HSC maintenance, including pluripotent gene Sox2 and chemokine gene Cxcl9. By performing biochemical experiments, I discovered that GOF mutant p53, but not WT p53, interacts with histone methyltransferase EZH2 and enhances histone H3 lysine 27 trimethylation (H3K27me3) at genes, including Mef/Elf4 and Gadd45g, that negatively regulate HSC self-renewal. Collectively, these findings demonstrated that GOF mutant p53 drives pre-leukemic HSC development through modulating epigenetic pathways. Thus, our studies have uncovered novel mechanistic and functional links between GOF mutant p53 and epigenetic regulators in pre-leukemic HSCs. This research may identify epigenetic regulator EZH2 as a novel target for the prevention and treatment of MDS patients with TP53 mutations.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19026号 / 農博第2104号 / 新制||農||1030(附属図書館) / 学位論文||H27||N4908(農学部図書室) / 31977 / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 今井 裕, 教授 久米 新一, 教授 松井 徹 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20272号 / 医博第4231号 / 新制||医||1021(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山田 泰広, 教授 藤渕 航, 教授 一山 智 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Objective: Child maltreatment (CM) is a widespread problem associated with poor mental and physical health outcomes. The underlying mechanisms of this link are not always well understood, however certain biological changes observed in maltreated individuals may play a role in connecting experience and outcome. This review specifically focuses on two markers of biological embedding, DNA methylation (DNAm) and telomere length (TL) in maltreated children and youth. As biomarker changes are not uniform among maltreated children, we additionally discuss biological and environmental resilience factors that may contribute to variability. Methods: We conducted a systematic review of Medline, Embase and PsycInfo databases for studies examining DNAm and/or TL in maltreated children and youth. Methodological quality of the included articles was assessed using the Scottish Intercollegiate Guidelines Network (SIGN) checklists for cohort studies and randomized control trials. Data extraction focused on various factors including population and CM (type, chronicity, severity, and duration) characteristics. Results: The initial search returned 1,688 non-duplicate results, with 417 full text articles reviewed. Twenty-six articles from 16 studies were ultimately included of which 8 examined telomere length and 18 examined DNA methylation. Conclusions: While some heterogeneity of findings was found, evidence supports differential changes in both biomarkers associated with CM. This review enhances understanding of the constellation of biological changes related to CM and consideration of the important role of resilience factors in mitigating risk. Elucidating these factors may highlight targets for future study and intervention development. / Thesis / Master of Science (MSc) / Child maltreatment is a serious problem linked to poor mental and physical health outcomes. The mechanisms of these links are not always clear, however biological changes observed in some maltreated individuals may play a role. Here, we systematically review literature related to two biomarkers of interest in maltreated children, telomere length and DNA methylation. Findings are varied; however, overall, they support an association between child maltreatment and changes in both biomarkers. We additionally discuss factors that may confer resilience related to these changes to highlight potential targets for future study and interventions.