Advisory Committee Chair
Michael A Miller
Advisory Committee Members
Date of Award
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Fertilization is the process by which male and female gametes join to give rise to a new organism. Union of sperm and ova requires that sperm be able to successfully locate and migrate towards oocytes in the female reproductive tract. By analyzing the in vitro migration of sperm from diverse species and mapping the complex architecture of their female reproductive tracts, we can infer that sperm must respond to directional cues to seek out the mature oocyte. However, the internal fertilization schemes of most complex animals complicate the analysis of in vivo sperm migration. The transparent epidermis of the nematode Caenorhabditis elegans has allowed for the gain of important insight into in vivo cell interactions. My goal in this dissertation was to delineate the cell signaling pathways that regulate directional sperm motility using the genetic tools available in the C. elegans model. Using fluorescent microscopy, we developed an assay for the in vivo observation of C. elegans sperm migration. Genetic screening for mutant animals with defects in sperm motility identified genes involved in polyunsaturated fatty acid (PUFA) synthesis, transport, and metabolism. In humans, PUFAs are precursors for prostaglandins, important lipid mediators of cell signaling. Microinjection of prostaglandins into PUFA–deficient hermaphrodites rescues non cell–autonomous sperm velocity defects. Using mass spectrometry techniques, we identified a group of novel F–series prostaglandins which are produced in oocytes and are required for normal sperm motility. We also show that the production of these oocyte–specific prostaglandins is mediated by insulin and other neuroendocrine signaling mediators via regulation of the DAF–16/FOXO transcription factor. Additionally, the release of prostaglandins from oocytes is regulated by the upstream action of the gap–junctional protein innexin 14 in pre–oocyte germ cells. Cumulatively, these data support the model that insulin signaling regulates the transport of prostaglandin precursors to oocytes. In oocytes, prostaglandins are produced and released into the proximal gonad to direct sperm to the site of fertilization. Release of these prostaglandins from oocytes requires the function of innexin 14 in oocyte precursors. This dissertation provides insight into the molecular mechanisms that regulate metazoan sperm migration.
Edmonds, Johnathan Wesley, "Molecular Mechanisms Regulating Caenorhabditis elegans Sperm Migration" (2011). All ETDs from UAB. 1576.