Differential alterations in expressions of ryanodine receptor subtypes in cerebellar cortical neurons of an ataxic mutant, rolling mouse Nagoya

This study aimed to clarify changes in the spatial expressions of types 1, 2 and 3 ryanodine receptors (RyR1, RyR2 and RyR3) in the cerebellum of a Ca2+ channel α1A subunit mutant, rolling mouse Nagoya. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that the mRNA signal levels of RyR1 and RyR3 were altered in the rolling cerebellum, which exhibited lower densities of RyR1 bands and higher densities of RyR3 bands than in the control cerebellum. Quite consistent with the RT-PCR results, the staining intensity of RyR1 and RyR3 was altered in the rolling cerebellum. RyR1 immunostaining appeared in somata and the proximal dendrites of Purkinje cells, and the staining intensity of both subcellular regions was equally lower in all cerebellar lobules of rolling mice than in those of controls. Although RyR3 immunostaining appeared in the dendrites of granule cells, more intense RyR3 staining in rolling mice than in controls was uniformly observed throughout all cerebellar lobules. The present study further examined co-localizations of ryanodine receptor subtypes and voltage-gated Ca2+ channel α1 subunits in the rolling cerebellum. Somatodendritic RyR1 immunostaining in Purkinje cells overlapped with either a mutated Ca2+ channel α1A subunit (P/Q-type), or a Ca2+ channel α1C subunit (L-type; dihydropyridine receptor) immunostaining. Immunostaining of these α1 subunits also emerged in granule cells. Those results suggest non-region-related alterations in RyR1 and RyR3 expressions in the rolling mouse cerebellum. Such expressional changes in ryanodine receptor subtypes may be involved in Ca2+ channel α1A subunit gene mutation, and may alter regulation of intracellular Ca2+ concentrations in cerebellar cortical neurons.