Self-renewal mediates homeostasis across mammalian organ systems as the cellular components of mature tissues are continually replaced in the face of wear and tear, injury, infection, and malignancy. The hematopoietic and immune systems are crucial for organismal longevity and rely on the ability of progenitor cells to bifurcate in fate to produce mature terminally differentiated progeny while self-renewing to maintain more quiescent progenitors. Asymmetric cell division is associated with self-renewal of lymphocytes and hematopoietic progenitors, but the mechanisms underlying the cell biology of these processes remain incompletely understood. Here we show that metabolic signals in the form of differential anabolism and catabolism regulate asymmetric division and cell fate bifurcations. Key transcription factors, including TCF1 and IRF4 in lymphocytes and IRF8 in hematopoietic progenitors, occupy regulatory nodes where signals associated with metabolism and traditional cell fate determinants converge. Notably, anabolic PI3K/mTOR signaling was required for terminal differentiation of both lymphocytes and hematopoietic progenitors through the regulation of a constellation of nutrient uptake, mitochondrial turnover, reactive oxygen species production, and autophagy. Further, we found that antigen receptor signaling in lymphocytes organizes a cell-intrinsic polarity pathway of asymmetric intracellular membrane trafficking that is regulated by PI3K activity and associated with terminal differentiation. These results support a model wherein cell fate bifurcations are organized by metabolic signaling at the population and subcellular level to ensure self- renewal of progenitor and memory populations.

Metabolic activity is an important functional parameter of a living cell. Microscopic techniques are demanded to resolve the heterogeneity of metabolic activity from cell to cell and among subcellular compartments. Towards this, work in the Min lab has been dedicated to developing a prevailing metabolic imaging platform that couples chemical imaging by stimulated Raman scattering (SRS) microscopy with small vibrational tags on precursor molecules. This thesis describes efforts along metabolic imaging by SRS microscopy, with focus on visualizing protein and lipid homeostasis. Chapter 1 describes the design principle of metabolic imaging, including selection of vibrational tags and setup of SRS microscopy, and an overview of successful demonstrations of metabolic imaging in protein and lipid metabolism. Chapter 2 describes adoption of such principle to visualize protein turnover with 13C-phenylalanine metabolic labeling under steady-state condition and various perturbations. The rest of this thesis (Chapters 3-6) switches focus to fatty acid metabolism and cellular lipid homeostasis. As the minimal tagging in vibrational imaging preserves the physicochemical property of lipid molecules to the largest extent, it motivated me to revisit fatty acid metabolism from a biophysical perspective. Bearing the question in mind whether the non-equilibrium metabolic activity could drive phase separation in biological membranes, I thus look into the principle of membrane organization and its implication in biological membranes in Chapter 3. Then in Chapter 4, I describe the discovery and characterization of previously unknown phase separation in endoplasmic reticulum (ER) membrane caused by lipid synthesis. In this case, metabolic imaging by SRS enables identification of solid-like domains formed by saturated fatty acid (SFA) metabolites. This observation further raises the question whether phase separation bears any functional roles in the adverse effects of SFAs (or lipotoxicity). Towards this, Chapter 5 introduces the background of lipotoxicity including its definition and models. Then I review proposed mechanisms for lipotoxicity, which point to the central role of ER in mediating the stress transduction. In Chapter 6, I present our findings that suggest the association of the observed solid-like domains with ER structural remodeling and local autophagic arrest. Together, these efforts demonstrate the valuable capability of SRS imaging to reveal metabolic heterogeneity and how this aids in the investigation of metabolic stress.

No description available.

Copy of author's previously published work inserted. Includes bibliographical references (leaves 160-182). Concentrates mainly on the characterisation of the molecular mechanism of action of the tec protein tyrosine kinase using biochemical and genetic approaches.

Bibliography: leaves 139-165.

Bibliography: leaves 139-165. / ix, 183 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 2001

Copy of author's previously published work inserted. / Includes bibliographical references (leaves 160-182). / xi, 182 leaves, [57] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Concentrates mainly on the characterisation of the molecular mechanism of action of the tec protein tyrosine kinase using biochemical and genetic approaches. / Thesis (Ph.D.)--University of Adelaide, Dept. of Molecular Biosciences, 2001?

No description available.

Copy of author's previously published article inserted into back cover pocket. / Bibliography: leaves 157-214. / iv, 214, [131] leaves, [19] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The function of receptor tyrosine kinase, c-Kit is examined in relation to the role of receptor levels in factor dependence and cell transformation and the function of several naturally occurring isoforms of the human c-Kit receptor were analyzed by expressing cDNA encoding these isoforms in murine cells. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1996

Thesis (Ph.D.)--Tufts University, 1992. / Submitted to the Dept. of Chemical Engineering. Adviser: Randall W. Swartz. Includes bibliographical references (leaves 243-247). Access restricted to members of the Tufts University community. Also available via the World Wide Web;