Compartmentation of the mouse cerebellar cortex by neuronal calcium sensor-1

Neuronal calcium sensor-1 (NCS-1) is a member of the EF-hand calcium-binding protein superfamily, which is considered to modulate synaptic transmission and plasticity. The detailed distribution of NCS-1 was analyzed in the mouse cerebellar cortex. In coronal sections, the NCS-1 immunostaining displayed characteristic parasagittal banding pattern in the Purkinje cell layer and molecular layer, while there were no apparent bands in the granule cell layer. The alternating positively and negatively NCS-1-labeled Purkinje cell clusters contributed to this cerebellar compartmentation. In contrast, stellate-basket cells were uniformly NCS-1-positive throughout the cerebellum. Immunofluorescent double staining showed that NCS-1 and zebrin II exhibited a similar parasagittal banding pattern. Then, we performed mapping of NCS-1- and/or zebrin II-labeled Purkinje cell somata using seven sequential coronal sections. NCS-1-positive/zebrin II-positive Purkinje cell clusters were seen throughout the cerebellum, but NCS-1-positive/zebrin II-negative Purkinje cells were exceedingly rare. On the other hand, NCS-1-negative/zebrin II-positive Purkinje cell clusters were found in anterior lobule vermis and paraflocculus, whereas they were rarely seen in posterior lobules. The digitized quantitative analysis showed close relationship between NCS-1 and zebrin II immunoreactivity in the molecular layer. The correspondence between NCS-1 and zebrin II demonstrated here indicates a novel anteroposterior difference of cerebellar compartmentation and provides fundamental information of cerebellar organization.