Müller 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 feature of vertebrate retinae that is structurally not understood. Here we provide in vitro evidence that Muller glia processes stabilize cells within columns. Dissociated embryonic chick retinal plus pigmented cells regenerate in vitro into fully laminated stratospheroids. After reaggregating chick and quail cells, quail-derived spheroid areas are detected as isolated sectors, as shown by a quail-specific antibody. Each sector contains one or multiple cell columns. The radial borders separating 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 the inner plexiform areas far into chick sectors. After selective damage of Muller cells by the gliotoxin DL-α-aminoadipic acid, the columnar organization is destabilized, as evidenced by a decrease in vimentin expression and by the migration of individual neurons out of their cell column. These data demonstrate that Muller cells actively stabilize cells within their columns, while neuritic growth is not hindered.