The hemopoietic system Is organized as a hierarchy of hemopoietic cell populations distinguished by differences in their proliferation and differentiation potential. Studies using short-term in vitro and in vivo assays based on colony formation in semi-solid medium, or in the spleens of lethally irradiated mice, respectively, have shown that these procedures detect primarily lineage-restricted progenitor types and have provided much information about the characteristics and regulation of such cells. Assessment of lymphoid and myeloid tissue reconstitution after more prolonged periods following transplantation has established the existence of a more primitive stem cell type; however, the retrospective nature of these complex analyses has Impeded characterization and purification of these cells. My first objective was to develop a procedure for the selective isolation of stem cells with short-term in vitro and in vivo multilineage differentiation potential. For this I devised a single-step, four-parameter fluorescence activated cell sorting procedure In which cells were selected according to their forward and orthogonal light-scattering properties, and their surface expression of the Thy-1 and H-2K antigens. Application of this procedure to marrow cells from mice treated 4 days previously with 150 mg/kg of 5-fluorouracil showed that it could be used to sort a subpopulation that was enriched 100-fold in CFU-GEMM and in which 1 in 4 cells was a day 12 CFU-S. To determine the extent to which stem cells with long-term lympho-myeloid repopulating potential had been copurified, I undertook to develop a quantitative procedure that might allow this primitive cell population to be measured and hence characterized on a routine basis. This required an assay that would detect donor-derived hemopoiesis exclusively, and that was sensitive enough for the detection of limiting numbers of cells with long-term lympho-myeloid repopulating potential. This was shown to be possible using a competitive repopulation assay in which lethally irradiated female recipients were transplanted with male "test" cells together with a second suspension of female cells with adequate short-term repopulating activity but greatly diminished long-term repopulating potential. These sex differences were then used to specifically identify the 5 week progeny of stem cells in the test suspension. Assessment of the sorted day 4 5-FU marrow population revealed that it was capable of repopulating all hemopoietic organs after transplantation and that an enrichment of 30-fold over unseparated, 5-FU-treated marrow had been achieved. My second objective was to determine whether the competitive long-term lymphoid and myeloid repopulation obtained with these sorted cells was due to the activity of Individual stem cells with a dual potential for lymphopoiesis and myelopoiesis. For this I used retroviral-infection to uniquely mark sorted cells In vitro, and then transplanted them in sufficiently low numbers to allow individual regenerated clones to be detected and analyzed. In some mice, distribution of cells with the same unique integration marker in different lymphoid and myeloid cell populations established the presence of lympho-myeloid stem cells in the original sorted population. In addition, clones with restricted tissue distributions were also documented. My final objective was to investigate whether the competitive repopulation assay was in fact able to serve as a procedure for the exclusive quantitation of long-term lympho-myeloid repopulating stem cells. A limiting dilution approach was used to compare the frequency of hemopoietic stem cells (competitive repopulating units, CRU) in marrow obtained from a variety of sources, using >20% repopulation by male cells at 5 or 10 weeks post-transplantation as the end point. The results obtained were largely independent of the time of analysis, and whether repopulation of recipient marrow or thymus was evaluated, suggesting that either can be used in this assay to quantitate a hemopoietic stem cell with the potential to regenerate both lymphoid and myeloid systems. These studies have provided procedures for the detection, quantitation and selective enrichment of the most primitive stem cells in the murine hemopoietic system which have competitive long-term lympho-myeloid repopulating ability. The availability of these procedures should facilitate the development of additional purification steps leading to the isolation of these cells as homogeneous suspensions, and their further use as targets for retrovirus-medilated gene transfer to determine the genetic basis of their activation, determination and neoplastic transformation. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

The overall goal of the work, described in this thesis was to investigate the molecular mechanisms that regulate normal pre-B cell proliferation and how these may be altered in transformed pre-B cells. Monoclonal antibodies and molecular biological techniques have allowed a number of stages of pre-B cell differentiation to be defined but little is known about mechanisms controlling their proliferation. Studies of pre-B cell production in animal models and in long-term cultures that support pre-B cell proliferation have suggested that stromal cells play a key role in this regard. As a first step to investigate the mechanisms involved, a number of pre-B cell supportive murine stromal cell lines were isolated and characterized. A number of pre-B cell lines were also isolated, cloned and characterized. From these, spontaneous and Abelson murine leukemia virus transformants were derived. These cell lines were then used in co-culture experiments to demonstrate that stromal cells constitutively secrete a pre-B stimulating factor. Characterization of the pre-B cell stimulating activity produced by one stromal cell line (M2-10B4) showed it to be a 10 Kd molecule sensitive to freezing and different from any cloned hemopoietic growth factor described to date. The possibility that extracellular matrix components might be involved in stromal cell-mediated control of pre-B cell growth was also investigated. It was found that pre-B cells attach specifically to fibronectin and that although fibronectin by itself cannot support pre-B cell proliferation, it contributes to stromal cell stimulation of pre-B cell growth. Both of these mechanisms were found to be affected in malignantly transformed pre-B cell populations irrespective of the mode of transformation. Transformed pre-B cells were found to have acquired the ability to secrete a novel 3 Kd autocrine factor that is also capable of stimulating normal pre-B cells. In addition transformed pre-B cells showed a greatly decreased ability to adhere to fibronectin and had become insensitive to the synergistic stimulating effect of fibronectin. It will be of interest to determine in the future whether these findings have a counterpart in human malignant pre-B cell populations. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20092号 / 農博第2199号 / 新制||農||1046(附属図書館) / 学位論文||H29||N5026(農学部図書室) / 33208 / 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 松井 徹, 教授 久米 新一 / 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21656号 / 医博第4462号 / 新制||医||1035(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 髙橋 良輔, 教授 浅野 雅秀, 教授 井上 治久 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

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Limbal stem cells maintain the corneal epithelium through a process of clonal growth and ordered migration. In X-inactivation mosaic female mice, that express LacZ from one of their X-chromosomes, random clumps of LacZ-positive cells are seen in the cornea at 3-6 weeks of life. This pattern resolves between 6-10 weeks forming radial stripes thought to represent chords of clonally related, inwardly migrating cells. By measuring the number and width of stripes and correcting for the effects of different proportions of LacZ-positive cells, an estimate of the number of coherent stem cell clones maintaining the tissue can be derived. Analysis at 5 ages demonstrated that the estimated number of coherent stem cell clones is reduced from ~100 at 15 weeks to ~50 at 39 weeks and is then stable at least until 52 weeks. An automated method was developed using image analysis software to analyse these striping patterns. This method produced results that did not differ significantly from the above. The dosage of the transcription factor Pax6 is crucial for normal eye development. In Pax6 heterozygous animals the estimated number of coherent stem cell clones is reduced to ~50 at 15 weeks with no further reduction up to 30 weeks. Mice hemizygous for the PAX77 transgene over-express human PAX6. In PAX77 hemizygous X-inactivation mosaics, estimated clone number was similarly reduced to ~50 with no further decline. Mice heterozygous for both Gli3 and Pax6 have a distinct striping phenotype, highlighted by an increase in coherent clones. When the corneal epithelium is injured the surrounding epithelial cells migrate along the corneal stroma to cover the wound. X-gal staining of healed, centrally wounded X-inactivation eyes reveals that striping patterns are reconstituted during wound healing in ex-vivo culture. In GFP mosaics the healing process can be imaged using time-lapse confocal microscopy. This technique demonstrated that clones remain contiguous throughout their migration. Healing of peripheral wounds was observed to form de-novo whorling patterns, revealing that basal cells in the epithelium can migrate both away from and towards the limbal region.

Migraine is a highly prevalent headache disorder imposing a significant burden of disability on human health worldwide. The headache is believed to arise from activation of trigeminal pain pathways, with CNS regions also playing an integral role in attack initiation and progression. Recent genetic associations have been made, but there is a need to convert these into relevant experimental models to study underlying disease mechanisms. Herein, I detail functional analysis of two deleterious variants in the genes KCNK18 and SLC12A3, that segregate with migraine with aura in one large pedigree. Gene function has been studied in a range of cell models, from heterologous expression systems and primary neuronal cultures, to Induced Pluripotent Stem (iPS) cell-derived nociceptors. In this context, the protein products of KCNK18 and SLC12A3 have been shown to modulate parameters of neuronal excitability, including baseline membrane properties and firing patterns. Migraine attacks are not wholly attributable to perturbations in peripheral pathways. I have shown that these genes are also expressed within the CNS in a small number of discreet regions, suggesting a possible role in central processing. Utilizing recently defined genetic variants and physiological cell- based models, will provide a platform for mechanistic insights into migraine pathogenesis and allow for the development of drug screening assays for new migraine therapies.

Murine embryonic stem cells (ESCs) are self-renewing, pluripotent cells able to differentiate into cells of all three germ layers. Pluripotency and self-renewal are maintained primarily by the core transcriptional factors Nanog, Oct4 and Sox2, but require the cooperation of other factors and coregulators and an efficient telomere maintenance mechanism. In mammals, telomere maintenance is achieved via a telomerase reverse transcriptase (Tert) that acts together with an RNA component (Terc). Maintenance of functional telomeres is essential to allow ESC proliferation, nevertheless if and how it is involved in the achievement and preservation of cell differentiation is still unknown. Here, we used Tert deficient mouse ESCs to elucidate the role of telomere length in differentiation. We found that Tert-/- ESCs with critically short telomeres are delayed, but still capable, to achieve differentiation after leukemia inhibitory factor (LIF) withdrawal and all-trans retinoic acid (ATRA) treatment, but failed to maintain it after LIF re-introduction to the growth medium. Telomere shortening effect on differentiation was accompanied by pluripotency gene dysregulation (e.g. Nanog overexpression), DNA hypomethylation and epigenetic disorders. This phenotype of metastable differentiation could be rescued by telomere lengthening via re-introduction of Tert, depletion of Nanog via short hairpin RNA, or via enforced expression of the de novo DNA methyltransferase 3b. These results reveal an unanticipated role of telomeres in the epigenetic regulation of gene expression and cell fate determination during physiological or pathological processes.