WIDESPREAD EXPRESSION OF BETA-1 INTEGRINS IN THE DEVELOPING CHICK RETINA - EVIDENCE FOR A ROLE IN MIGRATION OF RETINAL GANGLION-CELLS

During extension of axons, critical neuronal interactions with extrace llular matrix (ECM) and other cells are thought to be mediated in part by heterodimeric beta 1 integrin receptors. In this report, we examin e the expression and function of beta 1 integrins in the developing ch ick retina. Expression of the beta 1 subunit, assayed by in situ hybri dization and antibody staining of dissociated cells, was widespread in undifferentiated neuroepithelial cells, before the initiation of axon s. Expression persisted in most retinal cell layers throughout embryon ic development, during and after axon extension. The repertoire of bet a 1-associated alpha subunits was examined using reverse transcription -polymerase chain reaction. In addition to the alpha 6 and alpha 8 sub units previously reported, chick homologues of the alpha 2 and alpha 4 subunits were detected. Developmental Northern blots revealed varying patterns of integrin subunit expression and showed that expression of beta 1 and the mRNAs of its associated alpha subunits are not always coregulated during retinal development. The timing and distribution of expression suggested that beta 1 integrins may be involved in other d evelopmental events in addition to axon extension. To address function s carried out by beta 1 integrins in the early retina, explanted eye c ups were incubated in the presence of function blocking anti-beta 1 an tibody and migration of newly born retinal ganglion cells (RGCs) was a ssessed. RGC migration from the ventricular zone to the vitreal border was significantly inhibited, suggesting that beta 1 integrins play a role in neuroblast migration in the retina. (C) 1996 Academic Press, I nc.