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OVERT AND LATENT PATHWAYS OF POLARITY SPECIFICATION IN ZYGOTES: THE HAPLOID-TO-DIPLOID TRANSITION

Rinonos, Serendipity Zapanta
http://rave.ohiolink.edu/etdc/view?acc_num=case1354902108

Abstract Details

2013, Doctor of Philosophy, Case Western Reserve University, Cell Biology.
Establishment of structural and biochemical asymmetry is fundamental for normal differentiation and function of diverse cell types, from unicellular prokaryotes to multicellular eukaryotes. Polarity specification, the establishment of an axis for directed growth and secretion, allows cells to achieve an asymmetrical state. This phenomenon is conveniently exemplified in the unicellular eukaryote S. cerevisiae, or budding yeast. The nature of the yeast life cycle facilitates the study of polarity specification, as an axis of polarity is established at the beginning of each mitotic cell cycle. The transition from haploid to diploid states involves complex signal transduction cascades, leading to cell cycle arrest, chemotropic polarized growth, cell-cell fusion and nuclear fusion, culminating in zygote formation. Following substantial remodeling of the cell wall, plasma membrane, and redistribution of cytoplasmic constituents, the newly-minted zygote enters the mitotic cell cycle and must establish a polarization axis for initial bud emergence and growth. Mechanisms of bud site selection have been characterized in both haploid and diploid mitotic cycles, but the nature of polarity establishment in the zygote remains uncharacterized. This dissertation documents two competing pathways for initial zygotic bud site selection: 1) an overt, medial pathway, independent of the Ras-like GTPase Bud1, and 2) a latent, Bud1-GTPase-dependent, non-medial pathway, elicited by deletion of the transmembrane protein Rax1 and/or elimination of mitochondrial DNA. In zygotes which lack functional mitochondria, expression of ATP1-111, a mutant of the F1F0-ATPase alpha subunit, largely restores wild-type budding patterns. These observations highlight initial zygotic polarity specification mechanisms as distinct from chemotropic, haploid, and diploid conventions. In summary, the current investigation describes mechanisms of polarity establishment in the phase of the life cycle immediately following cell-cell fusion and cell cycle re-entry, highlights distinct requirements for initial polarity specification in zygotes, extends the regulatory role of Rax1 in polarity specification, illustrates that Rax1 may influence cytoskeletal polarity independently of Bud1-GTPase activation, and documents a novel linkage between mitochondrial function and cell polarity establishment. In addition, a novel, flow cytometry-based method for zygote purification is described for facilitation of high-throughput, genome-wide studies.
Alan Tartakoff, PhD (Advisor)
Danny Manor, PhD (Committee Chair)
Piet De Boer, PhD (Committee Member)
Martin Snider, PhD (Committee Member)
Alan Zhu, PhD (Committee Member)
243 p.
Cellular Biology; Molecular Biology
polarity specification; cell polarity; yeast polarity; bud site selection; zygotes; budding yeast

Recommended Citations

Citations

  • Rinonos, S. Z. (2013). OVERT AND LATENT PATHWAYS OF POLARITY SPECIFICATION IN ZYGOTES: THE HAPLOID-TO-DIPLOID TRANSITION [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1354902108

    APA Style (7th edition)

  • Rinonos, Serendipity. OVERT AND LATENT PATHWAYS OF POLARITY SPECIFICATION IN ZYGOTES: THE HAPLOID-TO-DIPLOID TRANSITION. 2013. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1354902108.

    MLA Style (8th edition)

  • Rinonos, Serendipity. "OVERT AND LATENT PATHWAYS OF POLARITY SPECIFICATION IN ZYGOTES: THE HAPLOID-TO-DIPLOID TRANSITION." Doctoral dissertation, Case Western Reserve University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1354902108

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.