staggerer phenotype in retinoid-related orphan receptor α-deficient mice

Retinoid-related orphan receptor alpha (ROR alpha) is a member of the nuclear receptor superfamily. To study its physiological role we generated null-mutant mice by targeted insertion of a lacZ reporter gene encoding the enzyme beta-galactosidase. In heterozygous ROR alpha(+/-) mice we found beta-galactosidase activity, indicative of ROR alpha protein expression, confined to the central nervous system, skin and testis. In the central nervous system, the ROR alpha gene is expressed in cerebellar Purkinje cells, the thalamus, the suprachiasmatic nuclei, and retinal ganglion cells. In skin, ROR alpha is strongly expressed in the hair follicle, the epidermis, and the sebacceous gland. Finally, the peritubular cells of the testis and the epithelial cells of the epididymis also strongly express ROR alpha. Recently, it was reported that the ataxic mouse mutant staggerer (sg/sg) is caused by a deletion in the ROR alpha gene. The analysis of the cerebellar and the behavioral phenotype of homozygous ROR alpha(-/-) mice proves identity to sg/sg mice. Although the absence of ROR alpha causes dramatic developmental effects in the cerebellum, it has no apparent morphological effect on thalamus, hypothalamus, and retina, Similarly, testis and skin of ROR alpha(-/-) mice display a normal phenotype. However, the pelage hair of both sg/sg and ROR alpha(-/-) is significantly less dense and when shaved shows reluctance to regrow.