DIURNAL REGULATION OF PER REPEAT FAMILY IN THE SUPRACHIASMATIC NUCLEUS OF RAT-BRAIN

We have recently reported fluctuations in the expression of the period repeat sequence, pp2.5, during light-dark cycles in the suprachiasmat ic nucleus (SCN) of rat. Presently, we performed in situ hybridization which shows that the fluctuation of pp2.5 expression continues during constant darkness conditions in the SCN of rat. The light exposure du ring subjective night but not subjective day triggered its elevated ex pression in a time-dependent manner which is parallel to that of c-fos expression. In this review, the cloning and characterization of multi ple per repeat sequences from mouse genom and rat brain mRNA were summ arized. The abundance of a novel per repeat mRNA (designated as RB15) fluctuates during a light-dark cycle in the SCN. These findings sugges t that per repeat sequence may have a role for the mammalian circadian rhythms. The evolutionary relationship between the mammarian per repe at sequence and the Drosophila period gene is also discussed.