Basic Mechanisms and Implications of Non-Photic Entrainment of Circadian Rhythmicity.
Final rept. 1 Sep 92-31 Aug 95,
CHICAGO UNIV IL DEPT OF MEDICINE
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Mrs. Wisor and Lowery have been primarily involved in studies which seek to determine the effects of light on the expression of late response genes in the SCN. The VGF gene was identified in a screen for mRnAs induced by nerve growth factor in PCl2 cells. The gene encodes a 90 KDa protein of unknown function that has been localized immunocytochemically to the rodent circadian pacemaker, the suprachiasmatic nucleus SCN. We hypothesized that light pulses would induce VGF expression in the SCN. Vgf is induced at the mRNA level by a light pulse in the subjective night, a time when a light pulse also induces a behavioral phase shift. Interestingly, the induction of vgf does not appear to be an immediate early response, as it is detectable for at least 3-6 hrs following a light stimulus. Furthermore, vgf induction by light is blocked by anisomycin, a protein synthesis inhibitor. Thus, vgf appears to be a late response gene that is regulated both by the circadian clock and by light.
- Anatomy and Physiology