Follicle rupture is the final step of the complex ovulation program, which releases fertilizable oocytes. Despite intensive study in the past four decades, a comprehensive understanding of the molecular mechanisms of follicle rupture is still lacking, in part due to the limitation of mammalian model systems to utilize genetic screens. We recently developed a novel Drosophila system that allows rapid application of genetic approaches to reveal precise details regarding the molecular events of follicular rupture. Moreover, recent studies from our lab have shown that the basic cellular and molecular mechanisms of ovulation are highly conserved from flies to humans; for instance, both systems require matrix metalloproteinase (Mmp) activity for follicle rupture. Leveraging the wealth of genetic tools and our ex vivo ovulation assay, this project will systematically interrogate conserved factors that are required for the precise regulation of Mmp activity and follicle rupture Our preliminary data reveals that an increase in intracellular free Ca2+ is required for Mmp activation but not expression. Conversely, follicular NADPH oxidase (Nox), which generates reactive oxygen species (ROS), and the oxidative stress-induced c-Jun N-terminal kinase (JNK) pathway regulate spatiotemporal Mmp protein expression. Therefore, we propose to 1) elucidate the conserved calcium-dependent signal transduction pathways that are required for Mmp activation, 2) investigate the role of follicular ROS and JNK signaling in Mmp expression, and 3) identify novel follicular factors for Mmp regulation and ovulation using genetic screens. This work will provide a comprehensive understanding of the ovarian signaling networks that precisely regulate Mmp activity and follicle rupture, which would be difficult in mammalian model systems. The conserved nature of these signaling pathways will allow the knowledge gained from this study to be further validated in mammalian and human ovulation. Therefore, this work will ultimately reveal promising new drug targets for the alleviation of anovulatory infertility orfor contraceptive development, both of which are highly relevant to human health.

Public Health Relevance

Ovulatory disorders account for 30% of women's infertility. With the wealth of genetic tools, the ease of experimentation, and the considerable conservation of cellular and molecular mechanisms of ovulation, this project utilizes a novel Drosophila model to genetically interrogate conserved signaling pathways and identify novel follicular factors for matrix metalloproteinase regulation and ovulation. Through this work, we will gain mechanistic insights into the precise regulation of follicle rupture and ovulation, which will aid the development of new drug targets for contraception and for the alleviation of anovulation, menstrual irregularity, and infertility.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Research Project (R01)
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Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
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Taymans, Susan
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University of Connecticut
Schools of Arts and Sciences
United States
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Li, Wei; Young, Jessica F; Sun, Jianjun (2018) NADPH oxidase-generated reactive oxygen species in mature follicles are essential for Drosophila ovulation. Proc Natl Acad Sci U S A 115:7765-7770
Knapp, Elizabeth M; Deady, Lylah D; Sun, Jianjun (2018) Ex vivo Follicle Rupture and in situ Zymography in Drosophila. Bio Protoc 8:
Deady, Lylah D; Li, Wei; Sun, Jianjun (2017) The zinc-finger transcription factor Hindsight regulates ovulation competency of Drosophila follicles. Elife 6:
Knapp, Elizabeth; Sun, Jianjun (2017) Steroid signaling in mature follicles is important for Drosophila ovulation. Proc Natl Acad Sci U S A 114:699-704
Shen, Wei; Sun, Jianjun (2017) Dynamic Notch Signaling Specifies Each Cell Fate in Drosophila Spermathecal Lineage. G3 (Bethesda) 7:1417-1427