Immunohistochemical characterization of the orphan nuclear receptor RORα in the mouse nervous system

RORalpha is an orphan nuclear receptor. A deletion mutation in the RORalpha gene leads to severe cerebellar defects, known as the staggerer mutant mouse. Although previous in situ hybridization (ISH) studies have shown that RORalpha is highly expressed'in the cerebellum, especially in Purkinje cells, and in the thalamus, sufficient immunohistochemical (IHC) study has not yet been presented. I demonstrate here the IHC analysis of RORalpha using a specific anti-RORalpha antibody, in adult and developing mouse nervous system. RORalpha immunoreactivity was observed in the Purkinje cell and molecular layers of the cerebellum. The co-localization of RORalpha with calbinclin D-28K (CaBP) and parvalbumin indicates that RORalpha-positive cells were Purkinje cells, stellate cells, and basket cells. In addition to the cerebellum, strong to medium RORalpha immunoreactivity was found in the thalamus, cerebral cortex (mainly in the layer IV), dorsal cochlear nucleus (DCN), suprachiasmatic nucleus (SCN), superior colliculus, spinal trigeminal nucleus, and retina. The immunostaining was restricted in nuclei of neurons. Developmentally, RORalpha immunoreactivity was observed in the cerebellum and thalamus from embryonal day 16 (E16). The distribution of RORalpha immunoreactivity and RORa mRNA hybridization signal was almost coincident. However, the intensity of hybridization signal was not always parallel to that of immunoreactivity.