THE EXPRESSION PATTERN OF THE ORPHAN NUCLEAR RECEPTOR ROR-BETA IN THEDEVELOPING AND ADULT-RAT NERVOUS-SYSTEM SUGGESTS A ROLE IN THE PROCESSING OF SENSORY INFORMATION AND IN CIRCADIAN-RHYTHM

ROR beta is an orphan nuclear receptor related to retinoid and thyroid hormone receptors and is exclusively expressed in the central nervous system (CNS), Here we present an in situ hybridization analysis of th e distribution of ROR beta mRNA in the developing and adult rat CNS, T he receptor localizes to areas involved in the processing of sensory i nformation. In the cerebral cortex, ROR beta mRNA was exclusively dete cted in nonpyramidal neurons of layer IV and, less so, layer V. The hi ghest expression was found in primary sensory cortices, In the thalamu s highest ROR beta expression was found in the sensory relay nuclei pr ojecting to the respective cortical areas. In contrast, sensory projec tion neurons in the periphery, for example retinal ganglion cells and neurons of the sensory ganglia showed only little ROR beta expression, ROR beta is also expressed in areas involved in the generation and ma intenance of circadian rhythms - the suprachiasmatic nucleus, the pine al gland and the retina. In the latter two tissues, ROR beta mRNA abun dance oscillates with circadian rhythmicity peaking during the hours o f darkness, ROR beta mRNA could not be detected in striatum, hippocamp us, cerebellum, the motor nuclei of the cranial nerves or the ventral part of the spinal cord. During development, ROR beta is expressed in many areas as early as embryonic day (E) 15, anticipating the distribu tion pattern in the adult. Our data suggest that ROR beta regulates ge nes whose products play essential roles in the context of sensory inpu t integration as well as in the context of circadian timing system.