Analysis of Pcp-2/L7 gene expression and function.

摘要

The mouse Purkinje cell protein-2 (Pcp-2/L7, herein called L7) gene is specifically and abundantly expressed in cerebellar Purkinje cells and in retinal bipolar neurons. Recent studies suggested that L7 functions in the tuning of P/Q type Ca2+ channels by the modulation of G-protein coupled receptors. The goals of the present studies were to extend our understanding on L7 function and control of L7 gene expression. To better understand function of the L7 protein, we carried out a variety of behavioral tests to compare wild type and L7 knock-out (L7KO) mice. We show that L7KO mice have improved performance on accelerating rotarod and display sexually dimorphic sensorimotor behavioral changes. Our results support the idea that cerebellum plays a role in sensorimotor gating, and it functions in the mediation of sensory response, which is a non-traditional role for the cerebellum. We then expanded our studies to investigate L7 gene expression in the mouse cerebellum and eye. Here we report that a third isoform of L7, which we call L7C, is the only form expressed in the eye, while two isoforms, L7A and L7B, are abundantly found in the cerebellum. To determine the molecular and genetic mechanisms of the Purkinje cell-specific expression of L7, we carried out in vivo analyses where we show that L7 structural gene does not have any Purkinje cell-enhancement activity, and likely contains significant repressive activity. 0.9 kb L7 proximal promoter, on the other hand, acts as an enhancer to direct expression in the cerebellar Purkinje cells. This enhancer activity requires the position-dependent action of the structural gene. In the present study, we show that retinoic acid receptor related orphan nuclear receptor-alpha (RORalpha) is a major activator of L7 gene expression in vivo and in vitro. Work presented here will allow us to better understand the relationship between the cellular physiology and the animal behavior. Although previous studies with RORalpha focused on its role during the cerebellar development, our studies show that RORa is no longer just a cerebellar developmental control molecule, but a key determinant of cerebellar physiology, as it activates L7, which in turn modulates Ca2+ channels.