Germ Line and Somatic Cell Divergence in Animal Development

Swartz, Steven Zachary Z.

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Year:: 2015
Contributor:: Swartz, Steven Zachary Z (creator); Wessel, Gary (Director); Casey, Dunn (Reader); Larschan, Erica (Reader); Richard, Freiman (Reader); Delong, Alison (Reader); Brown University. BIOMED: Molecular Biology, Cell Biology, and Biochemistry (sponsor)
Genre:: theses
Subject:: germ line; PGC; Nanos; CNOT6; CCR4; FoxY; Wnt; beta catenin; Delta; Notch; Sea urchins; Notch genes
Extent:: 15, 228 p.
DOI: https://doi.org/10.7301/Z0C24TTC

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Abstract:: A critical event in animal development is when germ line cells, which will one day become competent for producing eggs or sperm, are segregated away from the terminally differentiating soma. The soma comprises all cells in the body that specialize into diverse tissues of the body, have sacrificed their reproductive capability, and will die with that generation. In contrast, the germ line will transmit all heritable information to the organism’s progeny. The molecular mechanisms in the embryo which endow the founding germ line cells, or primordial germ cells (PGCs), with their enduring reproductive potency are remarkably diverse across species. Generally speaking, PGCs are either specified early by maternally-supplied factors deposited into the egg, later in embryogenesis by inductive mechanisms, or by some combination thereof. I have investigated the continuum of these mechanisms in echinoderms, with particular emphasis on the sea urchin Strongylocentrotus purpuratus. The sea urchin specifies its PGCs, called the small micromeres (sMics) early at the 5th embryonic cleavage. The RNA-binding protein Nanos is then transcriptionally activated downstream of maternally-supplied Dishevelled and β-catenin. Beyond this transcriptional event, the sMics are generally transcriptionally repressed, a conserved feature of early PGCs. Nanos then represses the accumulation the CNOT6 deadenylase, which creates a uniquely stable environment for RNA in the sMics. The sMics are thus able to acquire and retain maternally-supplied germ line RNAs, which are instead degraded in somatic cells. At gastrulation, Delta/Notch signaling induces the mesoderm to express the transcription factor FoxY and additional Nanos RNA, which is essential for establishing the somatic niche for the sMics. In contrast to the sea urchin, the sea cucumber and the sea star specify their germ lines much later in development, after gastrulation. This later mode of germ line formation likely represents the ancestral strategy in echinoderms. My functional investigation of sea urchin PGC specification provides insight into how an early-forming germ line can evolve from an inductive ancestor, and integrates germ line development into the context of the maternal-to-embryonic transition.
Notes:: Thesis (Ph.D. -- Brown University (2015)

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Rights: In Copyright
Restrictions on Use: Collection is open for research.

Citation

Swartz, Steven Zachary Z., "Germ Line and Somatic Cell Divergence in Animal Development" (2015). Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0C24TTC

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Molecular Biology, Cell Biology, and Biochemistry Theses and Dissertations

Theses and Dissertations for the Molecular Biology, Cell Biology, and Biochemistry department.
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