OR04-1 Reproductive abnormalities associated with deletion of Gpr54 in mouse GnRH neurons

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: OR04-GnRH & Gonadotroph Biology & Signaling
Saturday, June 15, 2013: 11:30 AM-1:00 PM
Presentation Start Time: 11:30 AM
Room 135 (Moscone Center)
Horacio Javier Novaira*1, Gloria E Hoffman2, Yongbum Koo3, Andrew M Wolfe*1 and Sally Radovick4
1Johns Hopkins Univ Schl of Med, Baltimore, MD, 2Morgan State Univ, Baltimore, MD, 3Inje University, Gimhai, South Korea, 4Johns Hopkins Med Instit, Baltimore, MD
Introduction: The Kiss-Gpr54 signaling pathway in the GnRH neuron is thought to be critical for both the onset of puberty as well as the attainment of normal reproductive function. Our working model includes the hypothesis that kiss neurons synapse directly on GnRH neurons and influence GnRH gene expression and release by directly activating Gpr54 on the membranes of GnRH neurons. However, Gpr54 is present in other hypothalamic cells that may synapse with GnRH neurons, and no animal models are available to test the hypothesis of direct kiss regulation on GnRH neurons. In addition, only complete Gpr54 KO animals have been generated, which do not experience normal pubertal development and are infertile. In this study, we directly test the hypothesis that kiss neurons regulate GnRH expression through synapses that release kiss and activate Gpr54 on the plasma membrane of GnRH neurons.

Aim: To define further GnRH neuronal signaling by kiss-Gpr54 and resulting physiological outcomes.

Methods and results: A GnRH neuron-specific Gpr54 knockout (GnRH-Gpr54KO) mouse model was generated and reproductive development and fertility was assessed.  Exon 2 of Gpr54 was surrounded by LoxP sites in a targeting construct that also included a Frt flanked neomycinr selection cassette. The targeting construct was electroporated into ES cells, and six positive targeted clones were obtained. The Gpr54 “floxed” animals were crossed to GnRH-Cre mice. Cre recombinase expression in GnRH neurons produced a cell-specific Gpr54 KO. A delay in pubertal onset in females was observed. The mean day of vaginal opening in wild-type littermates was 27 (±0.20) days versus 39 (±1.4) days in GnRH-Gpr54KO mice (n=5, P≤0.001). The first day in estrus and estrous cycles were monitored by vaginal lavages. Absence of the first day in estrus and estrous cyclicity were observed in the GnRH-Gpr54KO female mice. In addition, infertility was observed in both female and male GnRH-Gpr54KO mice.

Conclusion: Taken together, these data provide in vivo evidence that Gpr54 in GnRH neurons is critical for reproductive development and fertility. This work provides new insight into the physiological role of Gpr54 in mediating GnRH neuronal function and mammalian reproduction.

Disclosure: SR: Ad Hoc Consultant, CVS/Caremark, Speaker, Novo Nordisk. Nothing to Disclose: HJN, GEH, YK, AMW

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This research was supported by the Eunice Kennedy Shriver NICHD/NIH R01 HD370246, and through cooperative agreement [partnership U01HD066432] as part of the Cooperative Partnerships to Promote Workforce Diversity in the Reproductive Sciences Program, and the NIH/NIDDK, Baltimore Diabetes Research and Training Center (DRTC) P60DK079637
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