Expression of 14-3-3 Protein Isoforms in Different Stages of Follicular Development in Adult Mouse Ovaries
Annual Meeting of the Society for the Study of Reproduction / Portland, Oregon, USA
14-3-3 proteins (YWHA or Tyrosine 3-Monooxygenase/Tryptophan 5-Monooxygenase Activation proteins) constitute a family of conserved proteins expressed in a wide variety of organisms ranging from plants to animals. They are key regulators in various important intracellular events including signal transduction pathways, protein trafficking, cell cycle control and embryonic development. However, more information is needed to characterize the functions of 14-3-3 in mammalian reproductive organs and gametes. There are seven mammalian isoforms of 14-3-3 (beta, eta, gamma, epsilon, sigma, tau/theta and zeta) encoded by different genes. We identified, for the first time, the 14-3-3 isoforms expressed in mouse ovarian follicles at different stages of development, and examined similarities and differences in patterns of their distribution. All isoforms of 14-3-3 were detected, except 14-3-3 sigma, by Western blotting of protein extracts from ovaries and oocytes using isoform-specific antibodies. Immunohistochemical staining of follicles in paraffin-embedded ovary sections recognized all isoforms, with some similarities as well as notable differences in relative amounts, localizations and patterns of expression in different cell types at various stages of follicular development. At each stage, immunostaining showed marked expression of all isoforms, except for a relatively lower intensity of expression of 14-3-3 tau in all follicular cells other than oocytes. Expression of each isoform appeared to be more in cytoplasm of oocytes than in corresponding germinal vesicles. Higher amounts of expression of all isoforms were noted in cells of corpora lutea as compared to surrounding interstitial cells. Marked staining of all 14-3-3 isoforms, except tau, was observed in atretic follicles identified by the presence of pyknotic cells. Each isoform, except 14-3-3 eta, was found to be expressed in varying extents along zonae pellucidae of oocytes in all secondary, early antral and Graafian follicles examined. Mural granulosa cells in secondary follicles showed prominent lack in expression of all isoforms of 14-3-3, except for zeta. Similar lack of expression of 14-3-3 beta was observed in mural granulosa cells in early antral follicles, and of beta, epsilon, gamma and sigma isoforms in mural granulosa cells of Graafian follicles. Accumulation of beta, gamma and sigma isoforms was noted in granulosa cells surrounding the antrum of early antral follicles. In contrast, all isoforms exhibited pronounced accumulation in granulosa cells lining antrum of Graafian follicles. Results of similarities and differences in features of expression of all isoforms were found to be consistent among all follicles at each stage of development, in multiple ovary sections from all adult mice of same age studied. Exploration of the differential patterns of expression of 14-3-3 isoforms in ovaries of adult mouse will help characterize potential 14-3-3 interactions with other key proteins involved in oogenesis and oocyte maturation and help to reveal the functional significance of specific 14-3-3 isoforms in follicular cells at different stages of ovarian folliculogenesis. The research was supported by the Eunice Shriver National Institute of Child Health and Development grant HD061869 to Douglas Kline.
Conference Proceeding Title
Biology of Reproduction
De, Santanu; Marcinkiewicz, Jennifer; and Kline, Douglas, "Expression of 14-3-3 Protein Isoforms in Different Stages of Follicular Development in Adult Mouse Ovaries" (2011). Biology Faculty Proceedings, Presentations, Speeches, Lectures. 327.