Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 120-140).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 70-92).

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medicine / Master / Master of Philosophy

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Botany / Master / Master of Philosophy

published_or_final_version / abstract / toc / Molecular Biology / Master / Master of Philosophy

The splotch (sp) mutation has been identified as a mutation in the paired box gene, Pax-3. Heterozygous mice carrying this mutation are phenotypically normal, with the exception of a white spot on their bellies. Homozygous embryos do not live to birth, and suffer from a wide range of developmental defects, all of which result from delayed neural tube closure, or inadequate neural crest cell migration. Most notably, homozygotes have an increased rate of spina bifida with or without exencephaly. Retinoic acid (RA), which has been shown to be very important in the development of a number of systems, was shown to cause a selective mortality of the homozygous splotch embryos when administered maternally at day 9 p.c. (Moase and Trasler, 1987). Since cellular retinoic acid binding protein (CRABP) is localized to the tissues which are affected by both the splotch gene, and retinoic acid teratogenesis, its expression patterns in the developing splotch embryo were examined. It was found that the distribution of CRABP mRNA is normal, but its expression levels are excessive in splotch homozygous day 9 mouse embryos.

Understanding the genetic control of gametogenesis is a central goal of developmental biology and is important for treating infertility in humans. An approach to identifying critical genes in mammals is to search for and study homologues of genes known to play key roles in other organisms. In the fly, Drosophila melanogaster, GUS protein is a component of nuage, an electron-dense aggregation in early germ cells, and is required for oocyte development. GUS physically interacts with VASA, an RNA helicase thought to regulate mRNA metabolism. I identified two murine genes, SSB-1 and SSB-4, that are similar to and likely homologues of gus. SSB-1, SSB-4 and GUS each contain two conserved regions, termed the SPRY domain and the SOCS box, respectively. SSB-1 and SSB-4 share about 75% sequence identity and about 70% identity with GUS. Both SSB-1 and SSB-4 RNA and protein were found to be express in mouse ovarian granulosa cells of all stages of folliculogenesis. These cells support oocyte development and also produce steroids. Unexpectedly, SSB-1 and SSB-4 were only weakly or not detectable in oocytes, that contrasts with the expression of GUS in Drosophila oocytes. However, SSB-1 mRNA and protein were expressed in male germ cells; specifically in spermatocytes and spermatids. SSB-1 in spermatids was localized in a specialized structure known as the chromatoid body. Although the function of this structure is not quite clear, it has been compared to nuage, and one of its components is MVH, the murine homologue of VASA. Finally, using RNAi technology, SSB-1 was transiently depleted SSB-1 from a granulosa cell line. These cells showed a transient decrease in expression of the gene encoding P450scc, the rate-limiting enzyme in steroid synthesis. Preliminary results also indicated a decrease in progesterone synthesis. Taken together, these results establish the expression pattern of murine homologues of Drosophila GUS in mouse ovary and testis, reveal it might play function in translation regulation in male spermatogenesis, and identify a potential role in steroidogenesis by ovarian granulosa cells.