Differential distribution of phospholipase C beta isoforms and diaglycerol kinase-beta in rodents cerebella corroborates the division of unipolar brush cells into two major subtypes

Sublineage diversification of specific neural cell classes occurs in complex as well as simply organized regions of the central and peripheral nervous systems; the significance of the phenomenon, however, remains insufficiently understood. The unipolar brush cells (UBCs) are glutamatergic cerebellar interneurons that occur at high density in vestibulocerebellum. As they are classified into subsets that differ in chemical phenotypes, intrinsic properties, and lobular distribution, they represent a valuable neuronal model to study subclass diversification. In this study, we show that cerebellar UBCs of adult rats and mice form two subclasses-type I and type II UBCs-defined by somatodendritic expression of calretinin (CR), mGluR1 alpha, phospholipases PLC beta 1 and PLC beta 4, and diacylglycerol kinase-beta (DGK beta). We demonstrate that PLC beta 1 is associated only with the CR+ type I UBCs, while PLC beta 4 and DGK beta are exclusively present in mGluR1 alpha(+) type II UBCs. Notably, all PLC beta 4(+) UBCs, representing about 2/3 of entire UBC population, also express mGluR1 alpha. Furthermore, our data show that the sum of CR+ type I UBCs and mGluR1 alpha(+) type II UBCs accounts for the entire UBC class identified with Tbr2 immunolabeling. The two UBC subtypes also show a very different albeit somehow overlapping topographical distribution as illustrated by detailed cerebellar maps in this study. Our data not only complement and extend the previous knowledge on the diversity and subclass specificity of the chemical phenotypes within the UBC population, but also provide a new angle to the understanding of the signaling networks in type I and type II UBCs.