Oscillation of Clock Genes in GnRH
This research focuses on understanding how the cells in the suprachiasmatic nucleus (SCN) function as the primary circadian pacemaker by communicating timekeeping information to other cells and organ systems. Little is known about how the SCN controls circadian rhythms within whole organisms. Circadian rhythms are characterized by diurnal changes in expression of certain clock genes, which oscillate according to the 24-hour day. The SCN likely communicates information regarding time of day to the periphery by regulating a variety of neural and endocrine events. This research project examines how the SCN controls circadian rhythms in the female reproductive system. The circadian system connects to the female reproductive system through synaptic connections between cells of the SCN and GnRH neurons in the hypothalamus of the brain. Therefore, it is likely that the SCN communicates directly with GnRH neurons to drive circadian rhythms in GnRH neurons. If the GnRH neurons have circadian rhythms, they will express circadian clock genes in a diurnal pattern. In this experiment, we examined if levels of clock genes oscillate in GnRH neurons. We focused on two clock genes, BMAL and PER2. Specifically, we looked at the intensity of expression of these clock genes during the morning versus the evening. Immunohistochemical analysis of BMAL and PER2 was performed in transgenic mice that express green fluorescent protein (GFP) on the GnRH promoter (GnRH/GFP mice). GFP fluorescence allows identification of GnRH neurons. Once GnRH neurons were identified, BMAL or PER2 levels in GnRH neurons were visualized by rhodamine immunofluorescence. An arbitrary scale was chosen to rate the level of expression of clock genes in the GFP stained GnRH neurons. Expression levels of BMAL were high in the ZT 4 mice and low in ZT 16 mice and expression levels of PER2 were low in ZT 4 mice and high in ZT 16 mice demonstrating that clock genes are oscillating in GnRH neurons.
School:
Purdue University at West Lafayette
Department:
Biology
Research Advisor:
Shelley Tischkau
Department of Research Advisor:
Veterinary Biosciences
Year of Publication:
2003