Beta 2 laminins modulate neuronal phenotype in the rat retina

The production of cell types in the vertebrate retina follows a stereotyped 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 photoreceptors ("rods") and have correlated changes in rod production with changes in the production of other cell types. In cultures in which few rods, but many Müller and bipolar cells, are produced, the production 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. Substitution 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 laminins may control the choice between rod photoreceptor and rod bipolar cell fates.