Resolution of the staggerer (sg) mutation from the neural cell adhesion molecule locus (Ncam) on mouse chromosome 9

Visuospatial abilities

The importance of the hippocampus and its anatomical connections, including the medial septum, thalamic nuclei, and neocortical regions in many spatial tasks including the Morris water maze, has been emphasized. Studies in mutant mice with cerebellar atrophy and in rats with electrolytic lesions of the cerebellum have indicated that the cerebellum has a role in visuospatial and visuomotor processes in the Morris maze. Directional deficits in the water have also been noted in rats whose cerebellum was exposed to X-rays during different developmental stages. Cerebellar interactions with the superior colliculus, the hippocampus, and the neocortex via thalamic nuclei are suggested to be the basis of the cerebellar modulation of directional sense in maze tests.

The structural integrity of ROR alpha isoforms is mutated in staggerer mice: cerebellar coexpression of ROR alpha1 and ROR alpha4

The recessive mouse mutation staggerer (sg) disturbs the normal development of cerebellar Purkinje cells and affects certain functions of the immune system. To identify the causative gene, we constructed high-resolution genetic and physical maps of the staggerer locus on mouse chromosome 9. The transcription unit of the orphan nuclear receptor ROR alpha was identified in the critical interval. Our mutational analysis confirms a recent report that the sg phenotype may be caused by a genomic deletion in the common coding region of the ROR alpha isoforms. Of the four different isoforms of the ROR alpha gene that are generated by a combination of alternative promoter usage and exon splicing that differ in their DNA-binding properties, isoforms ROR alpha1 and ROR alpha4 are specifically coexpressed in the murine cerebellum and human cerebellum. Thus, at least two isoforms of the murine ROR alpha gene are affected by the genomic deletion associated with the staggerer phenotype. Our finding of cerebellum-specific coregulation suggests that distinct sets of target genes regulated by the ROR alpha1 and ROR alpha4 isoforms are required for Purkinje cell development.