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The circadian system of c-fos deficient mice |
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| Authors: | G I Honrado Randall S Johnson D A Golombek B M Spiegelman V E Papaioannou M R Ralph |
| Institution: | (1) Departments of Psychology and Zoology, University of Toronto, 100 St. George Street, M5S 1A1 Toronto, Ontario, Canada;(2) Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA;(3) Tufts University, School of Medicine and Veterinary Medicine, Boston, Massachusetts, USA;(4) Present address: Hormone Research Institute, University of California San Francisco, San Francisco, California, USA;(5) Present address: Department of Genetics and Development, Columbia University, 10023 New York, USA |
| Abstract: | We examined the role of c-fos in the synchronization of circadian rhythms to environmental light cycles using a line of gene-targeted mice carrying a null mutation at this locus. Circadian locomotor rhythms in mutants had similar periods as wild-type controls but took significantly longer than controls to entrain to 12:12 light-dark cycles. Light-induced phase shifts of rhythms in constant dark were attenuated in mutants although the circadian timing of phase delays and advances was not changed. A functional retinohypothalamic projection was indicated from behavioral results and light-induced jun-B expression in the SCN. The results indicate that while c-fos activation is not an absolute requirement for rhythm generation nor photic responses, it is required for normal entrainment of the mammalian biological clock.Abbreviations SCN suprachiasmatic nucleus - RHT retinohypothalamic tract - IEG immediate early genes - NGF nerve growth factor - VIP vasoactive intestinal polypeptide - DD constant darkness - CT circadian time |
| Keywords: | Circadian rhythm Gene targeting Phase shift Entrainment Light cycle |
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