The oocytes of most sexually reproducing animals arrest in diplotene or diakinesis of meiotic prophase I. Human oocytes enter meiosis in the embryo and maintain prophase arrest for decades. Oocyte growth occurs during the period of prophase I arrest, which enables them to acquire competence to complete meiosis and to produce healthy progeny. Hormonal signaling and soma-germline interactions regulate meiotic resumption (oocyte meiotic maturation). Meiotic maturation is defined by the transition to metaphase I, and its hallmarks are nuclear envelope breakdown, rearrangement of the cortical cytoskeleton, and meiotic spindle assembly. A failure of oocytes to undergo meiotic maturation results in sterility, whereas improper execution of the meiotic divisions causes aneuploidy. The timing of meiotic maturation is crucial. If oocytes undergo meiotic maturation prematurely, their capacity to produce healthy offspring is diminished. The molecular mechanisms that control and coordinate oocyte growth and meiotic maturation are incompletely understood. This application seeks to fill this knowledge gap by studying conserved translational regulators that coordinate and control the meiotic maturation decision and the growth process. We address mechanistic questions about how intercellular signaling and translational regulation control meiotic resumption. Defects in oogenesis represent a major cause of human birth defects, miscarriage and infertility. Ethical and technical issues limit the mechanistic depth of human studies. Oocyte meiotic maturation is an ancient reproductive process and many of its defining features are deeply conserved in evolution. Model systems are thus indispensable to the analysis of female meiosis. Because the full-grown oocytes of most animals are transcriptionally quiescent, translational regulation is a major control point. Our understanding of how signaling controls translation to regulate oocyte growth and meiotic maturation is incomplete. We developed C. elegans as a genetic model for studying the control of meiotic maturation by hormonal signaling. Our work shows that C. elegans and mammals share remarkable similarities in the hormonal control of meiotic maturation.
Our Aims are 1) Elucidate how translational regulators control oocyte growth and meiotic maturation; 2) Define how the SACY-1 DEAD-box RNA helicase regulates oocyte meiotic maturation; and 3) Determine how soma-germline gap junctions regulate meiotic maturation. The proposed experiments will provide mechanistic insights into how intercellular signaling and translational regulation control key cellular events of oocyte meiotic maturation. This basic research in a genetic model system will generate fundamental knowledge relevant for understanding human reproduction.

Public Health Relevance

Defects in oocyte growth and the completion of meiosis (meiotic maturation) represent a major cause of human birth defects, miscarriage and infertility. Because ethical and technical issues limit the mechanistic depth of data obtained from human studies, model systems are invaluable for understanding the cellular events of female meiosis and their control. This application will delineate essential conserved mechanisms by which intercellular signaling and translational regulation coordinate and control oocyte growth and meiotic maturation in the nematode Caenorhabditis elegans.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
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Salazar, Desiree Lynn
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University of Minnesota Twin Cities
Schools of Medicine
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Huelgas-Morales, Gabriela; Greenstein, David (2017) Control of oocyte meiotic maturation in C. elegans. Semin Cell Dev Biol :
Tsukamoto, Tatsuya; Gearhart, Micah D; Spike, Caroline A et al. (2017) LIN-41 and OMA Ribonucleoprotein Complexes Mediate a Translational Repression-to-Activation Switch Controlling Oocyte Meiotic Maturation and the Oocyte-to-Embryo Transition in Caenorhabditis elegans. Genetics 206:2007-2039
Huelgas-Morales, Gabriela; Silva-GarcĂ­a, Carlos Giovanni; Salinas, Laura S et al. (2016) The Stress Granule RNA-Binding Protein TIAR-1 Protects Female Germ Cells from Heat Shock in Caenorhabditis elegans. G3 (Bethesda) 6:1031-47
Spike, Caroline A; Coetzee, Donna; Eichten, Carly et al. (2014) The TRIM-NHL protein LIN-41 and the OMA RNA-binding proteins antagonistically control the prophase-to-metaphase transition and growth of Caenorhabditis elegans oocytes. Genetics 198:1535-58
Starich, Todd A; Hall, David H; Greenstein, David (2014) Two classes of gap junction channels mediate soma-germline interactions essential for germline proliferation and gametogenesis in Caenorhabditis elegans. Genetics 198:1127-53
Spike, Caroline A; Coetzee, Donna; Nishi, Yuichi et al. (2014) Translational control of the oogenic program by components of OMA ribonucleoprotein particles in Caenorhabditis elegans. Genetics 198:1513-33
Kim, Seongseop; Spike, Caroline; Greenstein, David (2013) Control of oocyte growth and meiotic maturation in Caenorhabditis elegans. Adv Exp Med Biol 757:277-320
Oldenbroek, Marieke; Robertson, Scott M; Guven-Ozkan, Tugba et al. (2013) Regulation of maternal Wnt mRNA translation in C. elegans embryos. Development 140:4614-23
Rao, Meghana; Song, Wenqiang; Jiang, Aixiang et al. (2012) VAMP-associated protein B (VAPB) promotes breast tumor growth by modulation of Akt activity. PLoS One 7:e46281
Kim, Seongseop; Govindan, J Amaranath; Tu, Zheng Jin et al. (2012) SACY-1 DEAD-Box helicase links the somatic control of oocyte meiotic maturation to the sperm-to-oocyte switch and gamete maintenance in Caenorhabditis elegans. Genetics 192:905-28

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