Professional Experience
- Walther H. Ott Professor in Avian Biology, Department of Poultry Science, The Pennsylvania State University, July 1, 2009-present
- Professor of Physiology, Department of Biological Sciences, University of Notre Dame, 1993-2009
- Visiting Scientist, Department of Animal Sciences/Molecular Biology Program, September 1991-August 1992 (12-month sabbatical leave)
- Professor, Department of Animal Sciences, Rutgers University, 1990-1993
- Associate Professor with tenure, Department of Animal Sciences, Rutgers University, 1984-1990
- Director of the Graduate Program in Animal Sciences, Rutgers University, 1986-1993
- Associate Chair for Graduate Teaching and Research, Department of Animal Sciences, Rutgers University, 1986-1993
- Assistant Professor, Department of Animal Sciences, Rutgers University, 1981-1984
- Visiting Scientist, INRA, Station de Recherches Avicoles, Nouzilly, France, June-July 1980
- Postdoctoral Research Associate, Cornell University, 1978-1981
Program Objectives
Implications for the research in our laboratory pertain to both improving women's reproductive health, together with the broader objective of understanding patterns of ovarian function and follicle development among vertebrates whose reproductive strategy consists of producing a limited number of offspring combined with considerable maternal investment (e.g., mammals, birds and a few reptiles). Applications include the potential for enhancing the reproductive potential of threatened/endangered plus domesticated avian species, particularly broiler breeders in which an aberrant regulation of the follicular hierarchy results in suboptimal egg production.
Ovarian Follicle Selection
A major focus is to define the endocrine, cellular and molecular mechanisms that accomplish follicle selection, a process as yet undefined in any vertebrate. The selection of preovulatory follicles represents an event by which a species-specific number of ovarian follicles progresses from an undifferentiated to differentiated state in preparation for ovulation. This process is critical for maintaining normal reproductive cycles and is dependent upon a balance between the maintenance of follicle viability and the loss of excessive or nonviable follicles via follicle atresia. Notably, excessive atresia can ultimately result in infertility and/or early reproductive senescence (e.g., menopause). The domestic hen represents a unique and important animal model system for such studies due to the ability to reliably identify a small cohort of prehierarchal follicles from which a single follicle per day is recruited into the preovulatory hierarchy.
The working hypothesis of our ongoing studies is that follicle selection and final differentiation prior to ovulation results from the removal of inhibitory cell signaling within the granulosa cell layer. To date, the nature of inhibition has focused on MAPK/Erk and protein kinase C (PKC) cell signaling maintained by epidermal growth factor ligands (EGFL) produced in an autocrine and paracrine fashion. The alleviation from this inhibitory signaling within the selected follicle subsequently enables FSH-induced LH receptor (LHR) induction and the initiation of steroid production. Of particular note is the recent finding that following follicle selection, MAPK/Erk and PKC signaling transitions to become obligatory for the expression and optimal activity of steroidogenic acute regulatory (STAR) protein and maximal steroidogenesis required for ovulation.
Simplified working model depicting the transition in cell signaling requirements from undifferentiated granulosa cells in follicles prior to selection to a differentiated state within preovulatory follicles. In undifferentiated granulosa cells one or more EGF family ligand(s) (EGFL) produced in an autocrine and/or paracrine fashion signals through ErbB1 and/or ErbB4 receptors [Woods and Johnson, 2007] to inhibit FSH-induced StAR expression and, as a result, progesterone production via activation of Erk (P-Erk) and PKC signaling. At follicle selection, granulosa cells begin the transition from FSHR dominance to LHR dominance [You et al., 1996; Johnson et al., 1996]. Cell signaling via LHR/cAMP induces StAR protein expression (and phosphorylation; not depicted) through a PKC-dependent mechanism [Woods and Johnson, 2007], enabling progesterone synthesis via P450scc activity within the mitochondria. In addition, LHR activation induces rapid transcription of one or more EGFL, which can then signal via the ErbB receptor(s) to activate the Erk signaling cascade. This LH-induced up-regulation of EGFL is mediated via PKC [Woods and Johnson, 2007]. In turn, Erk signaling is required to maintain mitochondrial electrochemical membrane potential (ψm), a prerequisite for StAR activity [Woods et al., 2007].
Significantly, the selective loss of ovarian follicles by atresia occurs via apoptosis and this process is first evident within the granulosa cell layer. We have established that granulosa cells from atresia-susceptible prehierarchal follicles are highly susceptible to undergoing apoptosis, in vitro. By contrast, following selection for final differentiation preceding ovulation, preovulatory follicles are not normally subject to atresia, and cultured granulosa cells from such follicles are known to be highly resistant to apoptosis. Such studies are conducted using transfection to over-express single or multiple gene products in cultured cells as well as by the targeted decrease in expression following transfection with antisense constructs. For additional information and related publications pertaining to ovarian follicle growth, development and atresia mediated via apoptosis visit our web site at: http://www.nd.edu/~avianova/. On the other hand, a decrease or absence of normal apoptotic cell death can contribute to tumor formation. Accordingly, a second and related focus utilizes human granulosa tumor cell lines to assess the role of cell survival proteins and cell death pathways in tumor formation and resistance to chemotherapeutics.
Ovarian Tumors of Granulosa Cell Origin
We are currently studying a combination of membrane receptor-mediated, cytoplasmic signaling and nuclear transcriptional events which can be linked to the development and chemotherapeutic-resistance of granulosa cell tumors. One recently investigated pro-apoptotic factor is the naturally expressed cytokine, T umor Necrosis Factor- R elated A poptosis I nducing L igand (TRAIL). The potential for the use of TRAIL as a chemotherapeutic, alone or in combination with conventional agents, is of considerable interest given TRAIL's selective actions to promote apoptosis in transformed (tumor) cells, but not normal cells. These studies utilize both primary cultured granulosa cells together with cell lines established from human granulosa cell tumors.
Human granulosa tumor cell lines are currently being utilized to investigate the role of Inhibitor of Differentiation (Id) proteins as transcriptional regulators of cell proliferation, differentiation and apoptosis, within the context of cancerous cells.
Proposed pathway for TRAIL signaling in granulosa cells. Solid arrows depict activation of the extrinsic pathway via the death receptor, DR5/TVB. Red dotted arrows depict the predicted activation of the intrinsic pathway based upon the demonstrated expression of APAF-1 and caspase-9 mRNA in granulosa cells from both prehierarchal and preovulatory follicles. Dotted green arrows predict potential pathways by which TRAIL-induced apoptotsis is prevented, possibly via FLIPLong or decoy receptors (DcR), including osteoprotegerin (OPG). In addition, the potential exists for TRAIL to activate the receptor adaptor protein, RIP. Because TRAIL mRNA is normally expressed within ovarian stromal, thecal and granulosa tissues, it is predicted that TRAIL can act on granulosa cells in a paracrine and/or autocrine fashion (dashed lines). aCasp., activated caspase; DD, death domain; DED, death effector domain; tBid, truncated Bid. See Johnson et al., 2007 for additional details. For additional information about our research, see http://poultry.cas.psu.edu/Johnson/index.html.
Selected Publications
Woods D.C., Schorey, J.S. and Johnson, A.L. 2009. Toll-like receptor signaling in hen ovarian granulosa cells is dependent on stage of follicle maturation. Reproduction 137:987-996.
Johnson, A.L. and Woods, D.C. 2009. Dynamics of avian follicle development: Cellular mechanisms of granulosa cell development. Gen. Comp. Endocrinol. 163:12-17.
Johnson, A.L., Haugen, M.J., Woods, D.C. 2008. Role for inhibitor of differentiation/DNA binding (Id) proteins in granulosa cell differentiation. Endocrinology 149:3187-3195.
Woods, D.C., Alvarez, C., Johnson, A.L. 2008. Cisplatin-mediated sensitivity to TRAIL-induced cell death in human granulosa tumor cells. Gynecol. Oncology 108:632-640.
Woods, D.C., Liu, H.-K., Nishi, Y., Yanase, T., Johnson, A.L. 2007. Inhibition of proteosome activity sensitizes human granulosa tumor cells to TRAIL-induced cell death. Cancer Letters 260:20-27.
Woods, D.C., Haugen, M.J. and Johnson, A.L. 2007. Actions of epidermal growth factor receptor/mitogen-activated protein kinase and protein kinase C signaling in granulosa cells are dependent upon stage of differentiation. Biol. Reprod. 77:61-70.
Woods, D.C. and Johnson, A.L. 2007. Protein kinase C activity mediates LH-induced ErbB/Erk signaling in differentiated hen granulosa cells. Reproduction 133:733-741.
Johnson, A.L., Ratajczak, C., Haugen, M., Liu, H.K. and Woods, D.C. 2007. Tumor necrosis factor related apoptosis inducing ligand (TRAIL) expression and activity in hen granulosa cells. Reproduction 133:609-616.
Johnson, A.L. and D.C. Woods. 2007. Chapter 6. Ovarian dynamics and follicle development. In: Reproductive Biology and Phylogeny of Aves. B.G.M. Jamieson, Ed., Science Publishers, Inc., Plymouth, U.K., pp. 243-277.
Woods, D.C. and Johnson, A.L. 2006. Phosphatase activation by EGF family ligands regulates Erk signaling in undifferentiated hen granulosa cells. Endocrinology 147:4931-4940.
Woods D.C. and Johnson, A.L. 2005. Regulation of follicle-stimulating hormone receptor mRNA in hen granulosa cells relative to follicle selection. Biol. Reprod. 72:643-650.
Johnson, A.L., Bridgham, J.T. and Woods, D.C. 2004. Cellular mechanisms and modulation of activin A- and transforming growth factor ß1-mediated differentiation in cultured hen granulosa cells. Biol. Reprod. 71:1844-1851.
Bridgham, J.T., Wilder, J.A., Hollocher H. and Johnson, A.L. 2003. All in the family: Evolutionary relationships among vertebrate death receptors. Cell Death & Differentiation. 10:19-25.
Complete List of Publications (since 1993)
Awards and Honors
- Recipient of the Shilts-Leonard Teaching Award for the College of Science, University of Notre Dame, 2004
- Recipient of the New Jersey Agricultural Experiment Station/Cook College, Rutgers University Research Excellence Award. Awarded for sustained research excellence during the previous five years, 1992
Teaching - University of Notre Dame, 1993-2009
Undergraduate Teaching
- Comparative Integrative Physiology (BIOS 30421, 4 credit lecture); Co-instructor; Spring Semester, 1995-2009
- Comparative Integrative Physiology Laboratory (BIOS 31421L, 1 credit laboratory) Spring Semester, 1995-2009
- Human Reproduction and Society (BIOS 109; 3 credit lecture); Fall Semester, 1995-2001
- Ornithology field-course (BIOS 569), Practicum in Field Environmental Biology, UNDERC, Summer, 1998-2000
- Vertebrate Biology (BIOS 30404; 3 credit lecture/laboratory); Fall Semester, 2002-2008
- Served as Independent Research Advisor for >20 undergraduates during the academic year and/or for summer Fellowship programs (Howard Hughes, NSF/REU)
Graduate Teaching
- Topics in Physiology: Reproduction, BIOS 575; Team-taught; Fall 1994
- Graduate Physiology Seminar, BIOS 580; Fall 1994, Fall 1999, Spring 2004
Service to the Profession
- Editorial Board, Poultry Science, 1982-1988, 1992-1995; Associate Editor, 2005 to present
- Editorial Board, Journal of Animal Sciences, 1988-1991
- Editorial Board, Domestic Animal Endocrinology, 1990-1993
- Editorial Board, Journal of Endocrinology, 2008 to present
- Board of Reviewing Editors, Biology of Reproduction, 2009 to present
- Program Chair, Poultry Science Association Annual Meeting, 1989, University of Wisconsin
- Member of USDA NRI Competitive Grants Program Review Panel, Reproductive Biology Section, Washington, D.C., 1989, 1990, 1993, 1994, 2003, 2004, 2006
- USDA CSRS Review of University of Nebraska Department of Animal Science, 1993
- NIH Biochemical Endocrinology Study Section, Bethesda, MD, June 2001
- Program Chair, Society for the Study of Reproduction (SSR) Annual Meeting, Quebec City, Canada, 2005
- NIH Cellular and Molecular Integrative Reproduction Study Section, Bethesda, MD, October, 2005
- Society for the Study or Reproduction (SSR) representative to the Federation of American Societies for Experimental Biology (FASEB) Publications and Communication Committee. 2005-2008 and 2008-2011
- Society for the Study of Reproduction (SSR), Publications Committee member, 2008 to present
