Fig. 5. EGFR signaling controls cell-affinity. (A-C) Wild-type wing imaginal discs containing clones of cells ectopically expressing either EGFR (A), Rho (B) or Spi* (C), monitored for mirr-lacZ expression (red). Clones were induced during the first larval instar and are marked either by loss (A,B) or gain (C) of GFP expression (green). (A) EGFR-expressing clones located within prospective notum (arrows) intermix freely with surrounding cells, as indicated by their ‘wiggly’ borders. Some clones within the hinge ectopically express mirr-lacZ and these tend to adopt a circular shape and sort out from surrounding wild-type cells (black arrowhead). Other clones do not express mirr-lacZ and these intermix with surrounding cells (asterisk). Finally, the sorting out of high mirr-lacZ-expressing from neighboring cells can occur within the same clone (white arrowhead). (B,C) Clones of Rho- or Spi*-expressing cells located within the prospective wing hinge form ‘wiggly’ borders and induce circular patches of mirr-lacZ-expressing cells that tend to sort out from surrounding cells that do not express mirr-lacZ. The inset in the left panel of B shows the overlay between GFP and mirr-lacZ expression in the vicinity of the clone.