Rhythmic expression of ROR beta mRNA in the mice suprachiasmatic nucleus.

The expression of the brain rich orphan nuclear receptor ROR beta (retinoid-related orphan receptor beta) was investigated in the mouse brain by in situ hybridization using antisense cRNA probe. Positive ROR beta mRNA signals were detected in various parts of the brain with high expression in the suprachiasmatic nucleus (SCN). In the SCN, ROR beta mRNA signals showed a peak at early daytime (ZT/CT4) and a trough at early nighttime (ZT/CT16) in both light-dark and constant dark conditions. Light exposure at subjective night did not alter the expression level. These findings suggest that ROR beta is a new member of a transcription factor possibly related to the circadian pacemaking system.