Orchid: A member of the family Orchideae.from Greek orkhis, testicle

 

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Recent Fellows Supported
on the Reproductive Biology Training Grant

 
Andrea Coviello (Dr. William J. Bremner)
Regulation of Spermatogenesis in Men

Dr. Coviello's research is focused on the epidemiology of hormones in male aging and the hypothalamic-pituitary-testicular axis in male reproductive function, with particular emphasis on male hormonal contraception. She completed a masters degree in epidemiology in 2003 with the thesis “Androgens and the Insulin-like Growth Factor System in Normal Middle Age Men: Correlates of Serum Hormones and Binding Proteins Potentially Related to Prostate Cancer Risk.” She also works on the relationship between intratesticular testosterone levels and spermatogenesis. Understanding this may contribute to the development of more efficacious treatments for male infertility as well as a male hormonal contraceptive. She recently conducted a pilot study investigating the dose-response relationship between
human chorionic gonadotropin (hCG) and intratesticular testosterone levels. Endogenous gonadotropins, LH and FSH, were suppressed by administration of intramuscular testosterone enanthate, and testicular production of LH was then stimulated by hCG, which stimulates production of intratesticular testosterone. Intratesticular testosterone levels were determined by fine-needle aspirate of the testes. Knowledge of the response within the testicle to hCG will allow the design of future studies of spermatogenesis with a greater focus on the testicular environment. Analysis of data for this study is under way. Dr. Coviello is currently conducting a clinical study on the differential rate of gonadotropin suppression by various combinations of contraceptive agents, such as testosterone enanthate, levonorgestrel, and a GnRH receptor agonist, acyline.


Wu-Min Deng (Dr. Hanele Ruohola-Baker)
Role of Dystroglycan and other Genes in Oogenesis

One of the fundamental questions in sexual reproduction is how maternal information is stored in oocytes so that proper early embryonic development is guaranteed prior to the expression of zygotic genes. This question can be most readily analyzed in a model organism, Drosophila melanogaster, owing to its easy-to-manipulate genetic system, short life cycle and relatively low cost. Dr. Deng is interested in understanding how maternal determinants are localized at different sub-cellular regions in the oocyte to direct the establishment of embryonic axes in this model organism. Since the majority of mammalian genes have homologous sequences and conserved functions in Drosophila, and the biological complexity of Drosophila is comparable to that of a mammal, many of the lessons learned in Drosophila will help us to better understand the mammalian systems. The Drosophila oocyte is polarized along the anterior-posterior and dorsal-ventral axes. The establishment of oocyte polarity requires an intact cytoskeletal network and communication between the germline cells and overlying somatic follicle cells. Dr. Deng’s previous research led to the discovery that dystroglycan, a receptor for laminin, is required for oocyte polarization in Drosophila. Interestingly, it is reported that altered dystroglycan function causes reduced reproductive fitness in a mouse model. In the future, he will use genetic techniques in the Drosophila to investigate in detail the cellular and molecular function of dystroglycan during oogenesis. In addition, he plans to use a sensitized dystroglycan mutant background to test in vivo interactions with genes such as src and Grb2, which are known to interact biochemically with dystroglycan. He is also screening for novel dystroglycan-interacting genes using the so-called “modifier screens" technique. Once the modifiers are identified, their relationship to dystroglycan and function in ovarian development will be further investigated.


Ajamete Kaykas (Dr. Randall Moon)

Role of Wnt Signaling in Development

Dr. Kaykas’s research has focused on understanding the molecular events that occur in cells after Wnts bind and activate their cognate Frizzled and LRP receptors. Wnts comprise a family of secreted glycoproteins involved in specifying axis, cell movements, and cell fate in the developing vertebrate embryo. Constitutive activation of Wnt signaling in mouse and man leads to cancer, and Wnt signaling recently has been implicated in the development of the female reproductive tract.  Mice deficient in Wnt7a are sterile, and their reproductive tracts have developmental defects. Identifying components of the Wnt-signaling pathway will shed light on Wnt's role in development and disease. Dr. Kaykas is using both biochemical and genetic approaches to identify proteins that interact with Frizzled and LRP6. Multiple yeast 2-hybrid screens have been conducted with the intracellular tail of LRP6 (another receptor for WNT) and the intracellular loops and tail of Frizzled. From these screens, he has identified numerous Frizzled and LPR6 interacting proteins and is presently characterizing a couple of them. In collaboration with Norbert Perrimon's lab at Harvard, he is conducting a genome-wide RNAi screen in Drosophila cell lines to identify novel proteins involved in the Wnt-signaling pathway. In addition, it has become apparent that Frizzled can form homo- and hetero-oligomers, and when this oligomerization goes awry it may contribute to the human disease familial exudative vitreoretinopathy. Dr. Kaykas is author of three recent papers.

 

Christiana DelloRusso (Dr. Mary-Claire King)
Biology of Ovarian Development and Tumorigenesis in Women

Dr. DelloRusso is studying the biology of familial ovarian cancer. The evaluation of BRCA1-associated ovarian cancer is uniquely suited to this study because most cancers occur in pre-menopausal women, and there is increasing evidence that BRCA1 is associated with estrogen-dependent processes. Genomic instability is characteristic of BRCA1-associated breast and ovarian tumors. BRCA1 is thought to play a major role in the DNA damage response that functions to maintain genomic stability. Dr. DelloRusso has propagated a novel BRCA1-null human cancer cell line, UWB1.289, the first such cell line originating from ovarian tissue. The goals of her project are to characterize the cell line and to develop it as a model culture system for testing the pathogenicity of BRCA1 missense mutations. Experiments testing DNA repair and cell cycle checkpoint regulation in response to induced DNA damage will be performed. Evaluation of these processes in UWB1.289 cells may reveal new information about the role of BRCA1 in response to DNA damage in ovarian epithelial cells. The development of a functional assay for BRCA1 could demystify the effects of potentially deleterious, but currently uncharacterized, BRCA1 missense mutations for breast and ovarian cancer patients (who at present must contemplate severe prophylactic measures when found to carry these mutations). In addition, a better understanding of BRCA1 biology within the ovary should lend insight into the process of ovarian tumorigenesis as well as the role of BRCA1 in normal ovarian development and aging.

 

Gregory Fraley (Dr. Robert Steiner)
Neuropeptides Governing the Integration of Metabolism and Reproduction

Dr. Fraley has been a fellow in the Steiner lab since March, 2002. He was initially involved in a collaborative investigation to explore the effects of centrally administered GALP on feeding, body weight, and other behaviors in the rat and mouse. He and a graduate student with whom he worked, Stephanie Krasnow, are coauthors of a paper (Krasnow et al., Endocrinology 144:8113-8122, 2003). Next, he studied the effects of GALP and galanin, delivered centrally (ICV), on the expression of the immediate early gene product Fos in the hypothalamus of the rat. This experiment demonstrated that GALP and galanin produced a differential pattern of Fos expression throughout the forebrain. GALP induced high levels of Fos expression in hypothalamic areas known to be involved in feeding and reproductive control, most notably the PVN, caudal POA, horizontal limb of the diagonal band of Broca, the arcuate nucleus, and the median eminence. This is an exciting and important finding, suggesting that certain hypothalamic regions may express GALP-specific receptors. This work was recently published (Fraley et al., Endocrinology 144:1143-1146, 2003). Dr. Fraley has also studied the effects of metabolic factors that regulate GALP mRNA expression. The Steiner lab had shown that leptin induces the expression of GALP mRNA, and Dr. Fraley examined the effects of other insulin and metabolic fuels (glucose and fatty acids) on GALP mRNA expression. His experiments demonstrated that insulin regulates GALP expression independently of leptin and that glucose and fatty acids may also have a regulatory effect on the expression of GALP mRNA. He has also discovered that rats with streptozotocin-induced diabetes have markedly reduced GALP expression in the arcuate nucleus and that insulin and leptin can both reverse this effect. These results are being prepared for publication. Dr. Fraley is now taking a two-pronged approach to determining the physiologic significance of GALP. First, in collaboration with Jamie Baumgartner at Amgen, Inc., he is exploring the action of centrally administered GALP to regulate male-specific reproductive behaviors. Second, he is developing the single-cell microarray technology in collaboration with Dr. Paul Amieux of the Department of Physiology and Biophysics (University of Washington) and Dr. Susan Smith of the Oregon Health and Sciences University. This technology will allow us to analyze the whole complement of mRNA in only GALP neurons in response to experimental manipulations. These two collaborative research projects will greatly extend the current knowledge base for the role of GALP as the central mediator of the effects of metabolism on reproduction.

 

Ellen Ward (Dr. Celeste Berg)
Molecular Regulation of Oogenesis in Drosophila

Dorsal appendage formation during egg development in D. melanogaster provides an excellent model for understanding the molecular and cellular interactions necessary to create complex structures from simple epithelia. The dorsal appendage tubes are formed from an initially flat somatic follicular epithelium covering the oocyte. As a member of Dr. Berg’s lab, Dr. Ward proposed studies to examine the mechanism by which cells interpret positional information and coordinate cell-shape changes and rearrangements to generate a tube. In studies of wild-type and mutant egg chambers, Dr. Ward showed that two distinct cell types, the rholacZ and Broad cells, contribute to the dorsal appendage tubes. Initially, the rholacZ and Broad cells are in a flat epithelium. They then reorganize to form an asymmetric tube, with the rholacZ cells forming the ventral floor of the tube and the Broad cells forming a roof over the rholacZ cells. Although these cells rearrange to form a dorsal appendage tube, they never intermingle, suggesting that a boundary exists between them preventing mixing. Consistent with this hypothesis, the rholacZ and Broad cells express different levels of Fas3 and Cadherin, two homophilic adhesion molecules.  On the basis of her analysis, Dr. Ward proposed that signaling across the boundary separating the two types of cells choreographs the cell-shape changes and rearrangements necessary to make a tube from an initially flat epithelium. She plans to examine dorsal appendage formation in the absence of Notch activity, a well-known signaling molecule that functions at many boundaries during development. In summary, this work provides the foundation for investigating the link between the initial patterning events that specify the tube primordium and the subsequent morphologic changes necessary to generate a tube from a flat epithelium. Dr. Ward has published one paper (EJ Ward et al., GAL4 enhancer trap patterns during Drosophila development. Genesis 34:46-50, 2002) and has another in preparation (EJ Ward and CA Berg, Drosophila oogenesis as a model for epithelial morphogenesis during development).

 




 

 



 

   Center for Research in Reproduction and Contraception                                   Phone 206.616.1818 - Fax 206.616.0499
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