CEPU-1, A NOVEL IMMUNOGLOBULIN SUPERFAMILY MOLECULE, IS EXPRESSED BY DEVELOPING CEREBELLAR PURKINJE-CELLS

Proteins of the immunoglobulin superfamily (IgSF) are involved in a va riety of specific cell-cell interactions in the developing nervous sys tem. We used a systematic approach, based on the PCR, to identify and characterize new members of this protein family in the developing chic k nervous system. In this study, we report on CEPU-1, a new IgSF prote in that is strongly expressed in developing Purkinje neurons in the ce rebellum and is detectable on the dendrites, somata, and axons of thes e cells. The timing of CEPU-1 expression coincides with the growth of the dendritic tree-after the Purkinje cells have finished their migrat ion from the ventricular zone. CEPU-1 is a 51 kDa glycoprotein compris ed of three Ig-like domains of the C2 subcategory and is anchored to t he plasma membrane via a post-translationally attached glycosyl-phosph atidylinositol moiety. The protein shows high sequence similarity to t he neurotrimin glycoprotein (78% identity), to the opioid-binding cell adhesion molecule (or OBCAM; 68% identity), and to the limbic system- associated membrane protein (or LAMP; 54% identity). Our results sugge st that CEPU-1 may serve as a cellular identification marker that is s pecific for developing Purkinje cells.