TARGET PREFERENCE OF EMBRYONIC RETINA CELLS AND RETINAL CELL-LINES ISCELL-AUTONOMOUS, POSITION-SPECIFIC, EARLY DETERMINED AND HERITABLE

Retinal ganglion cells (RGCs) form the topographic connection between retina and optic tectum in the developing avian embryo. In vitro, neur ons with the morphological traits and marker expression of RGCs were f ound both in single-cell cultures from embryonic day (E) 6 chick retin a and in retinal cell lines derived from E3.5 quail retina. Rapid and substantial differentiation of RGC-like cells could be induced in the lines by addition of fibroblast growth factor aFGF or bFGF. RGC-iike c ells were examined with respect to their target discrimination propert ies as single cells in the stripe carpet assay. In this assay system, alternating stripes of membrane vesicles prepared from the anterior an d posterior tectum are offered to growing axonal processes as a substr ate. Temporal RGC-like cells, both primary cells prepared from the tem poral retina and immortalized cells of those retinal lines derived fro m the temporal retina, avoid stripes of membrane vesicles from posteri or tectum; they prefer to grow on membrane vesicles from the anterior tectum, which is their in vivo target. Nasal RGC-like cells did not ex hibit a target preference, in accordance with previous findings. Toget her the experiments show that target preference of RGCs is a cell-auto nomous and heritable mechanism that is determined early and is positio n-dependent.