Honrado G I, Johnson R S, Golombek D A, Spiegelman B M, Papaioannou V E, Ralph M R
Department of Psychology, University of Toronto, Ontario, Canada.
J Comp Physiol A. 1996 Apr;178(4):563-70. doi: 10.1007/BF00190186.
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.
