The long-term goal of this project is to characterize the mechanisms that distinguish germ cells from somatic cells, a fundamental problem in developmental biology. In C. elegans, soma- germline asymmetries are established in the zygote before the first division, through the asymmetric partitioning of proteins and protein/RNA complexes in the cytoplasm. Cytoplasmic partitioning is regulated by conserved polarity regulators (PAR proteins), which localize asymmetrically in the zygote cortex. The goal of this proposal is to uncover how PAR activity at the cortex regulates polarity in the cytoplasm.
Specific Aim I (SA1) will focus on the mechanisms that segregate the RNA-binding protein MEX-5 to the anterior cytoplasm. Preliminary data suggest that MEX-5 asymmetry depends on phosphorylation by PAR-1, a kinase on the posterior cortex, which increases MEX-5 diffusion locally in the posterior cytoplasm. SA2 will focus on the germline determinant PIE-1, which segregate to the posterior, opposite MEX-5 and in a steeper gradient. We will investigate how PIE-1 integrates both cortical and cytoplasmic cues to form a distinct gradient. Finally, SA3 will focus on the mechanisms that localize P granules to the posterior. P granules are evolutionarily conserved RNA-protein complexes specific to the germline. We have discovered a new P granule component PPTR-1 for P granule integrity during mitosis;our initial findings suggest that the germline specificity of P granules depends on regulated assembly and does not require cytoplasmic partitioning. We will use a combination of biochemical, genetic, and live microscopy approaches to test each of these hypotheses, and identify the genes and biochemical interactions involved. Unlike other well-studied embryonic polarity models, our system does not rely on pre-localized RNAs to generate asymmetry, and thus gives us the unique opportunity to explore the mechanisms that directly segregate proteins in the cytoplasm.

Public Health Relevance

Cell polarity is essential to generate cell diversity during development, to prevent uncontrolled cell growth, and for the every-day functioning of many polarized cell types (epithelial cells, neurons, and lymphocytes). By taking advantage of a simple model system, our studies will illuminate the mechanisms that build and maintain the architecture of many cell types and prevent tumor formation.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Development - 1 Study Section (DEV1)
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Ravindranath, Neelakanta
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Johns Hopkins University
Schools of Medicine
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Chen, Bi-Chang; Legant, Wesley R; Wang, Kai et al. (2014) Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution. Science 346:1257998
Wang, Jennifer T; Seydoux, Geraldine (2013) Germ cell specification. Adv Exp Med Biol 757:17-39
Motegi, Fumio; Zonies, Seth; Hao, Yingsong et al. (2011) Microtubules induce self-organization of polarized PAR domains in Caenorhabditis elegans zygotes. Nat Cell Biol 13:1361-7
Voronina, Ekaterina; Seydoux, Geraldine; Sassone-Corsi, Paolo et al. (2011) RNA granules in germ cells. Cold Spring Harb Perspect Biol 3:
Griffin, Erik E; Odde, David J; Seydoux, Geraldine (2011) Regulation of the MEX-5 gradient by a spatially segregated kinase/phosphatase cycle. Cell 146:955-68
Voronina, Ekaterina; Seydoux, Geraldine (2010) The C. elegans homolog of nucleoporin Nup98 is required for the integrity and function of germline P granules. Development 137:1441-50
Zonies, Seth; Motegi, Fumio; Hao, Yingsong et al. (2010) Symmetry breaking and polarization of the C. elegans zygote by the polarity protein PAR-2. Development 137:1669-77
Merritt, Christopher; Seydoux, Geraldine (2010) The Puf RNA-binding proteins FBF-1 and FBF-2 inhibit the expression of synaptonemal complex proteins in germline stem cells. Development 137:1787-98
Gallo, Christopher M; Wang, Jennifer T; Motegi, Fumio et al. (2010) Cytoplasmic partitioning of P granule components is not required to specify the germline in C. elegans. Science 330:1685-9
Cheng, Ken Chih-Chien; Klancer, Richard; Singson, Andrew et al. (2009) Regulation of MBK-2/DYRK by CDK-1 and the pseudophosphatases EGG-4 and EGG-5 during the oocyte-to-embryo transition. Cell 139:560-72

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