Synchronous activation of gonadotropin-releasing hormone gene transcription and secretion by pulsatile kisspeptin stimulation

• Published in: Proceedings of the National Academy of Sciences - PNAS 2013-04, Vol.110 (14), p.5677-5682
• Main Authors: Choe, Han Kyoung, Kim, Hee-Dae, Park, Sung Ho, Lee, Han-Woong, Park, Jae-Yong, Seong, Jae Young, Lightman, Stafford L., Son, Gi Hoon, Kim, Kyungjin
• Format: Article
• Language: English
• Subjects: Activity Cycles - physiology; Animals; ARNTL Transcription Factors - deficiency; Biological and medical sciences; Biological Sciences; Chronobiology; Circadian rhythm; Endocrinology; Fundamental and applied biological sciences. Psychology; Gene expression; Gene expression regulation; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Genes; Gonadotropin-Releasing Hormone - metabolism; Hormonal regulation; Hormones; Hypothalamus - metabolism; Kisspeptins - administration & dosage; Kisspeptins - pharmacology; Luciferases; Mice; Mice, Transgenic; Nerve Net - metabolism; Neurochemistry; Neurons; Neurons - metabolism; Neuroscience; Pituitary gland; Proteins; Pulsatile Flow; Rodents; Secretion; Sex hormones; Transcription, Genetic - drug effects; Transcription, Genetic - physiology; Ultradian rhythm; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: nervous system and sense organs
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1213594110

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.