Abstract
Aldolase C (Aldoc, also known as “zebrin II”), a brain type isozyme of a glycolysis enzyme, is expressed heterogeneously in subpopulations of cerebellar Purkinje cells (PCs) that are arranged longitudinally in a complex striped pattern in the cerebellar cortex, a pattern which is closely related to the topography of input and output axonal projections. Here, we generated knock-in Aldoc-Venus mice in which Aldoc expression is visualized by expression of a fluorescent protein, Venus. Since there was no obvious phenotypes in general brain morphology and in the striped pattern of the cerebellum in mutants, we made detailed observation of Aldoc expression pattern in the nervous system by using Venus expression in Aldoc-Venus heterozygotes. High levels of Venus expression were observed in cerebellar PCs, cartwheel cells in the dorsal cochlear nucleus, sensory epithelium of the inner ear and in all major types of retinal cells, while moderate levels of Venus expression were observed in astrocytes and satellite cells in the dorsal root ganglion. The striped arrangement of PCs that express Venus to different degrees was carefully traced with serial section alignment analysis and mapped on the unfolded scheme of the entire cerebellar cortex to re-identify all individual Aldoc stripes. A longitudinally striped boundary of Aldoc expression was first identified in the mouse flocculus, and was correlated with the climbing fiber projection pattern and expression of another compartmental marker molecule, heat shock protein 25 (HSP25). As in the rat, the cerebellar nuclei were divided into the rostrodorsal negative and the caudoventral positive portions by distinct projections of Aldoc-positive and negative PC axons in the mouse. Identification of the cerebellar Aldoc stripes in this study, as indicated in sample coronal and horizontal sections as well as in sample surface photos of whole-mount preparations, can be referred to in future experiments.
Highlights
Aldolase is an enzyme involved in one of the essential steps in glycolysis, a process required in all cells that consume glucose
No differences were obvious in behavior, development, or reproduction between the homozygous (AldocVenus/Venus), heterozygous (Aldoc+/Venus) and wild-type (Aldoc+/+) mice in ordinary breeding conditions, detailed behavioral phenotype analysis was not performed in the present study
Astrocytes in the granular layer were found to express Venus. These results indicate that Bergmann glial cells and astrocytes do express Aldolase C (Aldoc) to some extent in the cerebellar cortex, their expression of Venus was much weaker than that of typical Aldoc-positive Purkinje cells (PCs)
Summary
Aldolase is an enzyme involved in one of the essential steps in glycolysis, a process required in all cells that consume glucose. Each longitudinal compartment determined by the striped Aldoc expression pattern (Aldoc compartments) is innervated by climbing fibers originating from a specific subarea of the inferior olive [9,10,11,12,13], and by mossy fibers of different sources to a certain extent [14,15,16]. PCs in Aldoc-positive and -negative compartments have different physiological properties [20,21]. These features of Aldoc compartments are generally consistent between individuals and are preserved across mammalian species from rodents to primates [18,22,23,24,25,26,27]. Aldoc compartments appear to reflect a basic organization of the cerebellar cortex
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