CD9 OF MOUSE-BRAIN IS IMPLICATED IN NEURITE OUTGROWTH AND CELL-MIGRATION IN-VITRO AND IS ASSOCIATED WITH THE ALPHA-6 BETA-1 INTEGRIN AND THE NEURAL ADHESION MOLECULE L1/

We describe here a novel monoclonal antibody (mab H6) which recognizes CD9, an integral cell surface constituent previously described in cel ls of the hematopoietic lineage and involved in the aggregation of pla telets, Mab H6 was raised against membranes of immature mouse astrocyt es and reacted with a protein of 25-27 kD in detergent extracts of adu lt mouse brain membranes, Sequence analysis of the N-terminal amino ac ids revealed an identity of 96% with CD9 from mouse kidney, CD9 was lo calized in the central and peripheral mouse nervous systems: in the sp inal cord of Ii-day-old mouse embryos, CD9 was strongly expressed in t he floor and roof plates, In the adult mouse sciatic nerve, myelin she aths were highly CD9-immunoreactive, Mab H6 reacted with the cell surf aces of both glial cells and neurons in culture and inhibited migratio n of neuronal cell bodies, neurite fasciculation and outgrowth of astr ocytic processes from cerebellar microexplants. Neurite outgrowth from isolated small cerebellar neurons was increased in the presence of ma b H6 on substrate-coated laminin, but not on substrate-coated poly-l-l ysine, Addition of mab H6 elicited an increase in intracellular Ca2+ c oncentration in these cells on substrate-coated laminin, Immunoprecipi tates of CD9 from cultured mouse neuroblastoma N2A cells contained the alpha 6/beta 1 integrin, Moreover, preparations of CD9 immunoaffinity -purified from adult mouse brain using a mab H6 column contained the n eural adhesion molecule L1, but not other neural adhesion molecules, C D9 bound to L1, but not to NCAM or MAG, Both the alpha 6/beta 1 integr in and L1 could be induced to coredistribute with CD9 on the surface o f cultured neuroblastoma N2A cells, The combined observations suggest that CD9 can associate with L1 and alpha 6/beta 1 integrin to influenc e neural cell interactions in vitro. (C) 1996 Wiley-Liss, Inc.