Fig. 4. Sens prevents Egfr pathway activation in the nucleus. UAS constructs were ubiquitously expressed in clones using flpout-GAL4. (A-A''') Co-misexpression of UAS-Egfr^act and UAS-lacZ posterior to the morphogenetic furrow (MF). Elav (red) is expressed in almost all cells within the clone (blue). Sens (green) is not detected within the clone. (B,C) Co-misexpression of UAS-Egfr^act and UAS-lacZ anterior to and within the MF. (B-B''') Elav (red) is expressed within and surrounding the clone (blue). Sens (green) is not expressed within the clone but is ectopically induced non autonomously. (C-C''') dpERK (red) and Sens (green) are expressed non-autonomously. Together, B and C are consistent with the presence of ectopic MFs surrounding areas of Egfr activation. (D-D''') Misexpression of UAS-Egfr^act anterior to the MF. pointed (pnt) transcription (pnt-lacZ, blue) occurs in most ectopic Elav-positive (red) cells. (E,F) Co-misexpression of UAS-Egfr^act and UAS-sens anterior to the MF. (E-E''') pnt transcription (pnt-lacZ, blue) does not occur and numbers of Elav-positive cells (red) are greatly reduced in the clone, which is marked by the Sens expressing cells (green). (F-F''') dpERK (red) is expressed autonomously at a high level within the clone, which is marked by Sens-expressing cells (green). Thus, sens is sufficient to block Egfr-induced pnt transcription, photoreceptor differentiation, and ectopic MF generation, but does not prevent dpERK induction.