MULLER GLIA STABILIZES CELL COLUMNS DURING RETINAL DEVELOPMENT - LATERAL CELL-MIGRATION BUT NOT NEUROPIL GROWTH IS INHIBITED IN MIXED CHICK-QUAIL RETINOSPHEROIDS

Radial columnar organization of cell clones is a characteristic featur e of vertebrate retinae that is structurally not understood. Here we p rovide in vitro evidence that Muller glia processes stabilize cells wi thin columns. Dissociated embryonic chick retinal plus pigmented cells regenerate in vitro into fully laminated stratospheroids. After reagg regating chick and quail cells, quail-derived spheroid areas are detec ted as isolated sectors, as shown by a quail-specific antibody. Each s ector contains one or multiple cell columns. The radial borders separa ting chick and quail sectors are fully congruent with the extension of 3A7-labelled Muller glia processes. While cell somata do not show any lateral interspecies mixing, quail-derived neuropil extends within th e inner plexiform areas far into chick sectors. After selective damage of Muller cells by the gliotoxin DL-alpha-aminoadipic acid, the colum nar organization is destabilized, as evidenced by a decrease in viment in expression and by the migration of individual neurons out of their cell column. These data demonstrate that Muller cells actively stabili ze cells within their columns, while neuritic growth is not hindered.