title: Synchronous activation of gonadotropin-releasing hormone gene transcription and secretion by pulsatile kisspeptin stimulation.
abstract: Pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH) is essential for pituitary gonadotrope function. Although the importance of pulsatile GnRH secretion has been recognized for several decades, the mechanisms underlying GnRH pulse generation in hypothalamic neural networks remain elusive. Here, we demonstrate the ultradian rhythm of GnRH gene transcription in single GnRH neurons using cultured hypothalamic slices prepared from transgenic mice expressing a GnRH promoter-driven destabilized luciferase reporter. Although GnRH promoter activity in each GnRH neuron exhibited an ultradian pattern of oscillations with a period of ∼10 h, GnRH neuronal cultures exhibited partially synchronized bursts of GnRH transcriptional activity at ∼2-h intervals. Surprisingly, pulsatile administration of kisspeptin, a potent GnRH secretagogue, evoked dramatic synchronous activation of GnRH gene transcription with robust stimulation of pulsatile GnRH secretion. We also addressed the issue of hierarchical interaction between the circadian and ultradian rhythms by using Bmal1-deficient mice with defective circadian clocks. The circadian molecular oscillator barely affected basal ultradian oscillation of GnRH transcription but was heavily involved in kisspeptin-evoked responses of GnRH neurons. In conclusion, we have clearly shown synchronous bursts of GnRH gene transcription in the hypothalamic GnRH neuronal population in association with episodic neurohormone secretion, thereby providing insight into GnRH pulse generation.
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Han Kyoung
authors.initials: HK
authors.lastname: Choe
authors.forename: Hee-Dae
authors.initials: HD
authors.lastname: Kim
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Han-Woong
authors.initials: HW
authors.lastname: Lee
authors.forename: Jae-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Seong
authors.forename: Stafford L
authors.initials: SL
authors.lastname: Lightman
authors.forename: Gi Hoon
authors.initials: GH
authors.lastname: Son
authors.forename: Kyungjin
authors.initials: K
authors.lastname: Kim
mesh_terms: D056930:ARNTL Transcription Factors / Q000172:deficiency; D000204:Activity Cycles / Q000502:physiology; D000818:Animals; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D059648:Kisspeptins / Q000008:administration & dosage / Q000494:pharmacology*; D008156:Luciferases; D051379:Mice; D008822:Mice, Transgenic; D009415:Nerve Net / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D011673:Pulsatile Flow; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D056930:ARNTL Transcription Factors; C538961:Bmal1 protein, mouse; C491407:Kiss1 protein, mouse; D059648:Kisspeptins; D007987:Gonadotropin-Releasing Hormone; D008156:Luciferases