As the ultimate regulator of reproductive function, Gonadotropin-releasing hormone (GnRH) is at the apex of the hypothalamic-pituitary-gonadal axis. It controls puberty, the menstrual cycle, fertility, menopause, and when disregulated, causes infertility. GnRH is secreted in a pulsatile pattern from a population of ~800 neurons, scattered throughout the hypothalamus, to regulate gonadotropins in the pituitary. The overall goal of this renewal application is to elucidate the molecular mechanisms that regulate GnRH in hypothalamic neurons at the levels of gene expression and pulsatile release, both in vitro and in vivo. We will utilize two major model systems: our immortalized GnRH-secreting hypothalamic cells (GT1) and genetically manipu- lated mice. Astonishingly, GT1 cells secrete GnRH in a pulsatile fashion with a 30 min periodicity mirroring mouse GnRH neurons in vivo. We have shown that this rhythm, as well as the estrous cycle, are dependent upon the circadian transcriptional loop. Furthermore, we have identified enhancer regions that target GnRH gene expression exclusively to cultured GT1 cells and to GnRH neurons in vivo. In addition, we have shown that the transcriptional regulators Dlx,Msx, Pbx, Prep, Meis, Oct-1, NF-1, GATA-4, Otx-2, and the Grg co- repressors act to control GnRH gene expression in vivo and in GT1 cells. We propose three aims:
Aim 1 will address regulation of the GnRH gene. Utilizing bioinformatics, we have identified additional upstream regula- tory regions and their roles in transcriptional control of the GnRH gene will be determined. Chromatin struc- ture and its role in differential regulation will be examined. Our goals include addressing the hypothesis that MAGE proteins lost in Prader-Willi Syndrome act to relieve Msx repression of the GnRH gene potentially explaining infertility in these patients.
Aim 2, will address the roles of Otx-2 and GATA-4 in development using GT1 cells in culture and GnRH-neuron-specific knock-out mice.
In Aim 3, we test the hypothesis that the GnRH neuron is a direct target of steroid hormones as well as responsive to afferent input from steroid- sensitive interneurons. We support this aim with preliminary data that GnRH pulses from GT1 cells are regulated by estrogen and progesterone in vitro. Overall, this proposal will address the molecular basis for the developmental regulation of GnRH gene expression and the mechanisms responsible for steroid modulation of GnRH gene expression and pulsatile secretion during the estrous cycle in vivo and in vitro.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK044838-21
Application #
7999253
Study Section
Integrative and Clinical Endocrinology and Reproduction Study Section (ICER)
Program Officer
Malozowski, Saul N
Project Start
1992-01-01
Project End
2012-08-31
Budget Start
2010-12-01
Budget End
2012-08-31
Support Year
21
Fiscal Year
2011
Total Cost
$304,214
Indirect Cost
Name
University of California San Diego
Department
Obstetrics & Gynecology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Schoeller, Erica L; Clark, Daniel D; Dey, Sandeepa et al. (2016) Bmal1 Is Required for Normal Reproductive Behaviors in Male Mice. Endocrinology 157:4914-4929
Hoffmann, Hanne M; Trang, Crystal; Gong, Ping et al. (2016) Deletion of Vax1 from Gonadotropin-Releasing Hormone (GnRH) Neurons Abolishes GnRH Expression and Leads to Hypogonadism and Infertility. J Neurosci 36:3506-18
Xie, Huimin; Hoffmann, Hanne M; Meadows, Jason D et al. (2015) Homeodomain Proteins SIX3 and SIX6 Regulate Gonadotrope-specific Genes During Pituitary Development. Mol Endocrinol 29:842-55
Skowronska-Krawczyk, Dorota; Zhao, Ling; Zhu, Jie et al. (2015) P16INK4a Upregulation Mediated by SIX6 Defines Retinal Ganglion Cell Pathogenesis in Glaucoma. Mol Cell 59:931-40
Glidewell-Kenney, Christine A; Trang, Crystal; Shao, Paul P et al. (2014) Neurokinin B induces c-fos transcription via protein kinase C and activation of serum response factor and Elk-1 in immortalized GnRH neurons. Endocrinology 155:3909-19
Breen, Kellie M; Mellon, Pamela L (2014) Influence of stress-induced intermediates on gonadotropin gene expression in gonadotrope cells. Mol Cell Endocrinol 385:71-7
Ahow, Maryse; Min, Le; Pampillo, Macarena et al. (2014) KISS1R signals independently of Gαq/11 and triggers LH secretion via the β-arrestin pathway in the male mouse. Endocrinology 155:4433-46
Hoffmann, Hanne M; Tamrazian, Anika; Xie, Huimin et al. (2014) Heterozygous deletion of ventral anterior homeobox (vax1) causes subfertility in mice. Endocrinology 155:4043-53
Roybal, Lacey L; Hambarchyan, Arpi; Meadows, Jason D et al. (2014) Roles of binding elements, FOXL2 domains, and interactions with cJUN and SMADs in regulation of FSHβ. Mol Endocrinol 28:1640-55
Witham, Emily A; Meadows, Jason D; Hoffmann, Hanne M et al. (2013) Kisspeptin regulates gonadotropin genes via immediate early gene induction in pituitary gonadotropes. Mol Endocrinol 27:1283-94

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