BETA-2 LAMININS MODULATE NEURONAL PHENOTYPE IN THE RAT RETINA

The production of cell types in the vertebrate retina follows a stereo typed time course. We have focused on a component of the extracellular matrix that may guide this schedule: the laminin beta 2 chain. Here, we have asked directly whether heterotrimeric laminins containing the laminin beta 2 chain can promote the production of presumptive rod pho toreceptors (''rods'') and have correlated changes in rod production w ith changes in the production of other cell types. In cultures in whic h few rods, but many Muller and bipolar cells, are produced, the produ ction of rods can be enhanced sixfold and that of bipolar cells can be reduced by 66%, by exposing cells to a laminin beta 2-rich matrix. Su bstitution of a laminin beta 2-depleted matrix (created with antisense RNA) returns the density of rods and bipolar cells to control levels. These linked alterations in phenotype expression suggest that laminin s may control the choice between rod photoreceptor and rod bipolar cel l fates.