Abstract not available

Bibliography: leaves 129-158. / xvii, 159, [11] leaves, [24] leaves of plates : ill. (some col.) ; 35 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The major estrogen inducible protein in zebra fish liver has been purified to homogeneity by FPLC using anion exchange chromatography (Mono-Q Pharmacia) with purification being monitored by SDS-PAGE electrophoresis. / Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 1995?

During animal development precise coordination and regulation of cell proliferation, differentiation and cell death is required for proper tissue organization. This is achieved through specific cell communication by intercellular signals. Cell death, for example, is a mechanism utilized by multicellular organisms for several developmental processes such as elimination of damaged cells or morphological shaping. Apoptosis can be induced by intrinsic signals generated within the cells or from extrinsic signals received from the surrounding environment. This work centered on the analysis of the mechanisms and signals that trigger apoptosis during Drosophila oogenesis. Drosophila ovaries are composed of approximately 16-20 ovarioles, each of which contains a series of egg chambers that are proceeding through the 14 stages of oogenesis moving from the germarium toward the oviduct. For the mature egg to be formed cell death has to occur at specific stages both in the germline (nurse cells) and in the somatic cells (follicle cells). However, whether this apoptosis is caused by intrinsic or extrinsic signals is not known. In addition to this developmentally controlled cell death, apoptosis can also be induced by environmental cues. Under starvation, for example, there is an increase of apoptosis at particular stages: in the germarium and at mid-oogenesis. Mid-oogenesis (stage8/9) is when vitellogenesis starts. At these stages the state of the egg chambers are checked in order to eliminate, through apoptosis of the germline, defective egg chambers. In starved flies, through activation of this “check-point”, oogenesis is blocked before vitellogeneis starts. It is not clear what are the signals that prevent apoptosis at mid-oogenesis in well-fed flies. In this study I have analyzed the function of a newly identified signaling molecule CG7447 during Drosophila oogenesis. My results indicate that CG7447 is required to prevent apoptosis at mid-oogenesis in well-fed flies. CG7447 RNA is only detectable in cells of the germarium, but not at later stages of oogenesis. When an HA tagged version of CG7447 (CG7447-HA) was expressed in the follicle cells of the germarium, this protein was found to be enriched in the oocyte during stages 2-8. These data suggest that CG7447 might be a secreted protein produced in the germarium, which is then secreted into the oocyte. To test the function of CG7447 during oogenesis, I generated a mutant allele. The mutation in CG7447 reduced female fertility. Mutant ovaries showed a block of egg chamber development at mid-oogenesis and this block correlated with apoptosis of the follicle cells. These mutant phenotypes could be reversed by expression of CG7447-HA, showing that these defects are due to the mutation in CG7447. Surprisingly, expression of CG7447-HA in the follicle cells only from stage 9 onward could restore fertility and normal oogenesis in a CG7447 mutant, indicating that CG7447 is required for follicle cell survival at later stages. Proper nutritional conditions are required to prevent apoptosis in the germline. Our data suggest that CG7447 is instead required to prevent apoptosis in the follicle cells. Thus, our analysis appears to have identified a novel signaling pathway that prevents survival of follicle cells in well-fed flies. Finally, our bioinformatic analysis showed that CG7447 is homologous to vertebrate EGF-like domain 7 (Egfl7) and EGF-like domain 8 (Egfl8) proteins. Importantly, expression of mouse Egfl7 or Egfl8 were able to confer normal oogenesis and fertility to CG7447 mutant flies. We therefore conclude that CG7447 is an evolutionary conserved protein and that CG7447 and Egfl7/8 share a common molecular function. CG7447 is a newly identified signaling molecule required during Drosophila oogenesis to promote the survival of follicle cells and to allow entry into vitellogenesis. Identification of the signaling cascade triggered by CG7447 will be important to more precisely understand its function during oogenesis. It may also help to reveal the molecular role of Egfl7/8 during vertebrate development.

Thesis (Ph. D.)--University of Missouri--Columbia, 2000. / "August 2000." Typescript. Vita. Includes bibliographical references (leaves 107-112). Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 147-158).

Establishment of cell polarity requires the involvement of several posttranscriptional regulatory mechanisms, including mRNA localization and translational control. A family of highly conserved RNA binding proteins in vertebrates, VICKZ (V̲g1RBP/V̲era, I̲MP-1, 2, 3, C̲RD-BP, K̲OC, Z̲BP-1) proteins, has been shown to act in these two processes. Previous studies of the posttranscriptional mechanisms mediated by VICKZ family members have been largely limited by the lack of genetic approaches in certain vertebrate systems. Identification of Imp, the Drosophila member of the VICKZ family, opened the possibility to use genetic approaches to investigate the roles of a VICKZ family member in mRNA localization and translational control. In this dissertation, we show that Imp is associated with Squid and Hrp48, two heterogeneous proteins (hnRNP) that complex with one another to regulate localized expression of gurken (grk). In addition, Imp binds grk mRNA with high affinity in vitro and is concentrated at the site of grk localization in midstage oocytes. Mutation of the Imp gene does not substantially alter grk expression, but does partially suppress the grk mis-expression phenotype of fs(1)k10 mutants. In contrast, overexpression of Imp in germ line cells results in mislocalization of grk mRNA and protein. The opposing effects of reduced and elevated Imp activities on grk expression suggest that Imp acts in regulation of grk expression, but in a redundant way. To further explore the mechanisms by which localized expression of grk is regulated by Imp, a deficiency screen was conducted to search for dominant modifiers of the dorsalized phenotype resulting from Imp overexpression. Twelve genomic regions were identified to contain dominant modifiers of the Imp overexpression phenotype. Further characterization of mutants of genes within these genomic regions led to identification of five modifiers, including cyclin E (cycE), E2f transcriptional factor 1 (E2f1), lingerer (lig), snail (sna) and mushroom body expressed (mub). E2f1 encodes a transcriptional factor that is involved in regulating the G1 to S phase transition during mitosis. Mutation of E2f1 results in altered grk mRNA and protein distribution within oocyte, revealing a role for this gene in regulation of grk expression. / text

published_or_final_version / abstract / Zoology / Master / Master of Philosophy

During the growth phase of oogenesis, mammalian oocytes increase several hundred-fold in volume. Although it is known that ovarian granulosa cells send growth promoting signals, neither these external signals nor the transduction pathways that become activated in the oocyte are known. Therefore, the presence and the activity of candidate signaling pathways in growing murine oocytes were investigated. By immunoblotting, the MAP kinases, ERK1 and ERK2, as well as their activating kinase MEK, were detected in oocytes at all stages of growth. However, using a phospho-specific anti-ERK antibody, no immunoreactive species were detectable in isolated granulosa cells or oocytes at any stage of growth, except metaphase II. Phosphorylated ERK was also present, although in smaller quantities, in oocyte-granulosa cell complexes at the later stages of growth. Furthermore, when ovarian sections were stained with an anti-ERK antibody, the protein was found to be highly concentrated in the cytoplasm of oocytes at all stages of growth, with lower levels in the nucleus. Another member of the MAP kinase family, Jun kinase (JNK), was investigated. By immunoblotting, JNK was detected in growing oocytes. Experiments using an anti-JNK antibody on ovary sections revealed the protein to be uniformly distributed in non-growing and growing oocytes with no evidence of preferential nuclear localization. These results imply that an interaction between the oocyte and the granulosa cells may be required to generate phosphorylated ERK. They also imply that growth signals probably are not relayed through ERK, but do not exclude a role for Jun kinase in mediating oocyte growth.

Early Drosophila development is a coordinated series of temporal and spatial events leading to specific localized gene expression. The maternally expressed gene Bicaudal-C (Bic-C) encodes a KH-domain RNA binding protein required in the developing oocyte for anterior-posterior patterning and follicle cell migration. The dominant heterozygous phenotype results in the development of embryos with bicaudal and head defects. A two-hybrid screen using BIC-C as "bait" identified the novel protein ANTIMEROS (ATMS) and the SH3-domain containing protein MILE END (MILE). / ATMS is highly conserved between humans and mice, its expression is almost entirely female-specific, and is limited to certain developmental stages. Mutant alleles for atms are able to dominantly enhance the phenotype of Bic-C heterozygotes confirming the Bic-C-atms interaction. Here I show that NOS mislocalization causes the trans-heterozygous phenotype, as introduction of a nos mutation strongly suppresses the bicaudal phenotype. nos transcripts show a hyper-polyandenylation in atms mutant ovaries, an indicator of translational activation, suggesting that ATMS and BIC-C function as translational repressors of nos through changes in its poly(A) tail length. / MILE, contains two highly conserved SH3 domains at the C-terminus. Experiments involving the analysis of mutant alleles and overexpression mile transgenic lines show that MILE is a negative regulator of both Torso and Egfr RTK signaling. Its not clear what functional role BIC-C may have with RTK signaling, but recent evidence suggests that posterior group gene expression influence terminal pole RTK signaling.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [85]-96).