Screen overview. (a) Neurogenic wave in medaka. Single confocal sections through eye stained for Ath5 mRNA at the level of the lens. The sections show the neurogenic wave during its initiation, progression and steady wave stage. (b) Current model of Ath5 regulation. Three stages of Ath5 regulation have been identified: initial repression in proliferating RPCs; activation and maintenance in the proneural state around the exit of cell cycle by Fgf8, NeuroD, Pax6, and Ath5 itself; and finally terminal downregulation in differentiating RGCs. (c) Schematic overview of transregulation screen. We individually cotransfected 8,448 Oryzias latipes cDNAs with pGL3 Ath5::Luc and a cytomegalovirus (CMV)-driven Renilla luciferase control vector (pRL-CMV) into BHK21 cells in 96-well plates. Each transfection was carried out in triplicate. Identified candidates were filtered using semi-automated in situ hybridization. FGF, fibroblast growth factor; Shh, Sonic hedgehog.