Chimeric Integrins Expressed in Retinal Ganglion Cells Impair Process Outgrowth in Vivo

Integrin function in retinal ganglion cell (RGC) development was examined in vivo by transfecting genes encoding various dominant forms of the chicken β1 integrin subunit into intact eye primordia of Xenopus embryos. RGCs expressing the chimeric chicken/Xenopus integrin receptors exhibited a marked reduction in process outgrowth with only 27% extending an axon and 41% bearing dendrites compared to control levels of 85-88%. None of the integrin constructs impaired the ability of RGC axons to pathfind appropriately or of retinal precursors to migrate to different laminar positions. Chimeric integrin expression also impaired process outgrowth in cells of the inner nuclear layer, although to a lesser extent than RGCs. Transfected diencephalic neurons, by contrast, showed normal levels of process outgrowth. These findings show that β1 integrins play an important role in regulating the outgrowth of axons and dendrites from RGCs in the retina but that chimeric integrins do not impair growth cone steering in general.