The number of Purkinje neurons and their topology in the cerebellar vermis of normal and reln haplodeficient mouse

The Reeler heterozygous mice (reln+/−) are haplodeficient in the gene (reln) encoding for the reelin glycoprotein (RELN) and display reductions in brain/peripheral RELN similar to autistic or schizophrenic patients. Cytoarchitectonic alterations of the reln+/− brain may be subtle, and are difficult to demonstrate by current histological approaches. We analyzed the number and topological organization of the Purkinje neurons (PNs) in five vermal lobules - central (II-III), culmen (IV-V), tuber (VIIb), uvula (IX), and nodulus (X) - that process different types of afferent functional inputs in reln+/+ and reln+/− adult mice (P60) of both sexes (n = 24). Animals were crossed with L7GFP mice so that the GFP-tagged PNs could be directly identified in cryosections. Digital images from these sections were processed with different open source software for quantitative topological and statistical analyses. Diversity indices calculated were: maximum caliper, density, area of soma, dispersion along the XZ axis, and dispersion along the YZ axis. We demonstrate: i. reduction in density of PNs in reln+/− males (14.37%) and reln+/− females (17.73%) compared to reln+/+ males; ii. that reln+/− males have larger PNs than other genotypes, and females (irrespective of the reln genetic background) have smaller PNs than reln+/+ males; iii. PNs are more chaotically arranged along the YZ axis in reln+/− males than in reln+/+ males and, except in central lobulus, reln+/− females. Therefore, image processing and statistics reveal previously unforeseen gender and genotype-related structural differences in cerebellum that may be clues for the definition of novel biomarkers in human psychiatric disorders.