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 extracellular matrix (ECM) and other cells are thought to be mediated in part by heterodimeric beta 1 integrin receptors. In this report, we examine the expression and function of beta 1 integrins in the developing chick retina. Expression of the beta 1 subunit, assayed by in situ hybridization and antibody staining of dissociated cells, was widespread in undifferentiated neuroepithelial cells, before the initiation of axons. Expression persisted in most retinal cell layers throughout embryonic development, during and after axon extension. The repertoire of beta 1-associated alpha subunits was examined using reverse transcription-polymerase chain reaction. In addition to the alpha 6 and alpha 8 subunits 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 developmental events in addition to axon extension. To address functions carried out by beta 1 integrins in the early retina, explanted eye cups were incubated in the presence of function blocking anti-beta 1 antibody and migration of newly born retinal ganglion cells (RGCs) was assessed. 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, Inc.