THE EXTRACELLULAR-MATRIX MOLECULE, LAMININ, INDUCES PURKINJE-CELL DENDRITIC SPINE PROLIFERATION IN GRANULE CELL DEPLETED CEREBELLAR CULTURES

Granule cells and glia were eliminated or reduced in organotypic cereb ellar cultures exposed to cytosine arabinoside. Transplantation of suc h granuloprival cultures with glia or exposure to astrocyte conditione d medium in the absence of parallel fibers (granule cell axons) result ed in proliferation of Purkinje cell dendritic spines. The aim of the present study was to identify specific astrocyte secreted factors that induced dendritic spine proliferation. Known astrocyte secreted, neur ite promoting factors were screened by application to granuloprival cu ltures and assayed for dendritic spine proliferation by electron micro scopy. An extracellular matrix molecule, laminin, evoked sprouting of Purkinje cell dendritic spines. Dendritic spine proliferation was not associated with known neurite promoting parts of the laminin molecule, as two laminin-derived peptides with identified neurite promoting dom ains did not induce dendritic spine sprouting. The purpose of laminin- induced dendritic spine proliferation may be to elaborate postsynaptic membrane, thereby increasing the target area for arriving axon termin als during development or regeneration, both of which have been associ ated with the presence of laminin secreting astrocytes. (C) 1998 Elsev ier Science B.V. All rights reserved.