Fig. 3. Loss of echinoid leads to sustained ERKA phosphorylation. (A,B) High levels of phosphorylated ERKA, a readout of Egfr signaling, are present in a single row of cell clusters within the morphogenetic furrow of wild-type discs (anti-dpERK, red, A,B); these clusters correspond to the Atonal-expressing proneural clusters (anti-Atonal, green, B). (C,D) In homozygous ed^l(2)k01102 eye discs, these clusters fail to lose dpERK signaling (red) as cells emerge from the morphogenetic furrow and retain high levels of signaling for several rows. Groups containing high levels of dpERK retain Atonal expression in two or more cells (anti-Atonal, green). (E,F) Patches of ed^l(2)k01102 tissue created using the FLP-FRT technique (absence of green in F) retain high levels of phosphorylated ERKA relative to surrounding wild-type tissue (anti-dpERK in red).