Research
Female germ cell development occurs in the context of an ovarian follicle, which contains a germ cell (oocyte or egg) and somatic granulosa and theca cells. Intercommunication between oocytes and granulosa cells is necessary for proper oocyte and follicular development. Research in our laboratory focuses on understanding the molecular and functional interactions between oocytes and granulosa cells that promote production of a fertile oocyte. This knowledge can then be used to (1) develop better therapeutic interventions for infertility or species preservation (2) develop better reproductive management tools for animal agricultural production and (3) allow the manipulation of the avian genome through genetic alterations of avian PGCs.
Currently there are three areas of research in the laboratory:
1. Interaction between oocytes and granulosa cells
It is well established that the bi-directional interaction between the oocyte and the surrounding granulosa cells is vitally important for oocyte and granulosa cell development. Members of the TGF-beta superfamily of signaling molecules are produced by both oocytes and granulosa cells and are indispensable for promoting oocyte and follicular development. These secreted molecules act by binding to cell surface receptors and activating SMAD proteins, which then influence gene transcription. Our laboratory uses transgenic technology and in vitro culture to uncover how SMAD-mediated signaling and other signaling pathways regulate oocyte growth and development. In addition, we are developing co-culture systems to examine the reciprocal relationship between oocytes and granulosa cells in birds using genomic and proteomic technology. Our objective is to isolate secreted products from mammalian and avian follicles that impact oocyte development and fertility.
2. Mechanisms regulating the differentiation of early female germ cells in mammals and birds.
Early events associated with germ cell development are difficult to study due to the small number of primordial germ cells and early oogonia present in fetal and newborn ovaries. We are developing an in vitro/in vivo model of germ cell development that will allow the genetic manipulation of precursor germ cells, while still providing a normal microenvironment for follicular development. In mice, we are inducing mouse ES cells to differentiate into primordial germ cells and transplanting these cells back into the ovary to complete development. In chickens, we will isolate primordial germ cells from chick embryos and transfect these cells with various DNA constructs expressing dsRNA (RNAi) to knock-down oocyte-specific transcripts. PGCs will then be transplanted into recipient embryos to complete their development. The successful production of oocytes using either mouse ES cells or transplanted avian PGCs will allow us to rapidly identify and test the function of novel and important genes involved in oocyte development.
3. Mechanisms regulating differences in reproductive capacity between broiler-breeder and laying hens.
Genetic selection for growth and composition (broilers) has led to a decrease in reproductive efficiency in broiler breeder hens compared to egg-laying hens. However, the mechanisms leading to decreased reproductive efficiency in broiler-breeders hens are unclear. We will determine the molecular differences, at the ovarian level, between broiler-breeder and laying hens using microarray, subtractive hybridization and immnoblot analysis. These molecular differences could then be used as therapeutic targets to increase reproductive efficiency or as selectable markers for breeding management.
Accomplishments
- Defined changes in MAPK signaling associated with the preantral to antral transition in mouse ovarian follicles
- Characterized the requirement for oocyte-secreted factors in specifying the cumulus granulosa cell phenotype and antagonizing the mural granulosa cell phenotype
- Identified SMAD2 signaling as a key oocyte-stimulated pathway in cumulus cells
- Characterized the differential regulation of the progesterone, estradiol, prostaglandin and AP-1 signaling pathways in porcine CL before and after acquisition of luteolytic capacity
- Determined that progesterone blocks PGF 2a -induced luteolytic responses in the porcine CL without luteolytic capacity
Publications
Diaz, F. J., K. Sugiura, and J. J. Eppig. 2008. Regulation of Pcsk6 expression during the preantral to antral follicle transition in mice: opposing roles of FSH and oocytes. Biol. Reprod. 78:176-183.
Sugiura, K., Y. Q. Su, F. J. Diaz , S. A. Pangas, S. Sharma, K. Wigglesworth, M. J. O'Brien, M. M. Matzuk, S. Shimasaki, and J. J. Eppig. 2007. Oocyte-derived BMP15 and FGFs cooperate to promote glycolysis in companion cumulus cells. Development 134:2593-2603.
Diaz, F. J. , K. Wigglesworth, and J. J. Eppig. 2007. Oocytes determine cumulus cell lineage in mouse ovarian follicles. J. Cell Sci. 120 1330-1340.
Diaz, F. J. , K. Wigglesworth, and J. J. Eppig. 2007. Oocytes are required for the preantral granulosa cell to cumulus cell transition in mice . Dev. Biol. 305:300-311.
Diaz, F. J. , M. O'Brien, K. Wigglesworth, and J. J. Eppig. 2006. The preantral granulosa cell to cumulus cell transition: Competence to undergo expansion. Dev. Biol. 299:91-104.
Diaz, F. J. and M. C. Wiltbank. 2005. Acquisition of luteolytic capacity: Changes in prostaglandin F 2a ? regulation of genes involved in progesterone biosynthesis in the porcine corpus luteum. Domest. Anim. Endocrinol. 28:172-189.
Diaz, F. J. and M. C. Wiltbank. 2004. Acquisition of luteolytic capacity : Changes in prostaglandin F 2a r egulation of steroid hormone receptors and estradiol biosynthesis in pig corpora lutea. Biol. Reprod. 70:1333-1339.
Mattos, R., C. R. Staples, A. Arteche, M. C. Wiltbank, F. J. Diaz, T. C. Jenkins, and W. W. Thatcher. 2004. The effects of feeding fish oil on uterine secretion of PGF 2a, composition, and metabolic status of periparturient holstein cows. J. Dairy Sci. 87:921-932.
Diaz, F. J., L. E. Anderson, Y. L. Wu, A. Rabot, S. J. Tsai, and M. C. Wiltbank. 2002. Regulation of progesterone and prostaglandin production in the CL. Mol. Cell Endocrinol. 191:65-80.
Diaz, F. J., T. D. Crenshaw, and M. C. Wiltbank. 2000. Prostaglandin F 2a induces distinct physiological responses in porcine corpora lutea after acquisition of luteolytic capacity. Biol. Reprod. 63:1504-1512.
Pyeon, D., F. J. Diaz, and G. A. Splitter. 2000. Prostaglandin E(2) increases bovine leukemia virus tax and pol mRNA levels via cyclooxygenase 2: Regulation by interleukin-2, interleukin-10, and bovine leukemia virus. J. of Virol. 74:5740-5745.
