Parasagittal compartmentation of cerebellar mossy fibers as revealed by the patterned expression of vesicular glutamate transporters VGLUT1 and VGLUT2

The cerebellum receives sensory signals from spinocerebellar (lower limbs) and dorsal column nuclei (upper limbs) mossy fibers. In the cerebellum, mossy fibers terminate in bands that are topographically aligned with stripes of Purkinje cells. While much is known about the molecular heterogeneity of Purkinje cell stripes, little is known about whether mossy fiber compartments have distinct molecular profiles. Here, we show that the vesicular glutamate transporters VGLUT1 and VGLUT2, which mediate glutamate uptake into synaptic vesicles of excitatory neurons, are expressed in complementary bands of mossy fibers in the adult mouse cerebellum. Using a combination of immunohistochemistry and anterograde tracing, we found heavy VGLUT2 and weak VGLUT1 expression in bands of spinocerebellar mossy fibers. The adjacent bands, which are in part comprised of dorsal column nuclei mossy fibers, strongly express VGLUT1 and weakly express VGLUT2. Simultaneous injections of fluorescent tracers into the dorsal column nuclei and lower thoracic–upper lumbar spinal cord revealed that upper and lower limb sensory pathways innervate adjacent VGLUT1/VGLUT2 parasagittal bands. In summary, we demonstrate that VGLUT1 and VGLUT2 are differentially expressed by dorsal column nuclei and spinocerebellar mossy fibers, which project to complementary cerebellar bands and respect common compartmental boundaries in the adult mouse cerebellum.