Figure 1.

scrib mutant clones expressing Bsk^DN ectopically proliferate and have disrupted cell morphology. Third instar larval eye/antennal imaginal discs (posterior to the left in all figures) containing eyFLP-induced MARCM clones expressing mCD8-GFP (green) to mark mutant tissue. Planar optical sections are shown (apical and basal sections through the same disc for some samples), except C, F, J, M which are cross sections (apical up). Grey scale is CycE (A, I, K), BrdU (B, L) and Elav (D-H, J, M-O). Red is phalloidin to mark F-actin (C-H, J, M-O). A white bar indicates the location of the MF. (A-E) FRT82B. Control eye disc clones exhibit the normal pattern of CycE expression (A) and BrdU incorporation (B) with asynchronous cycles anterior to the MF, a synchronous band of S phases just posterior to the MF and a further round of division of unspecified cells in the more posterior portion of the eye disc. In cross section (C), the columnar epithelial cell morphology is apparent, with apically localized photoreceptor cell nuclei (Elav positive), which are only seen in apical planar sections (D) and not in more basal sections (E). (F-H) FRT82B scrib¹. scrib mutant cells have altered cell morphology with many cells contracting beneath the epithelium resulting in the aberrant localization of Elav-positive photoreceptor nuclei basally within the eye disc. (I-J) FRT82B UAS-bsk^DN. Bsk^DN-expressing clones exhibit a normal pattern of CycE expression (I), and, in cross section, normal cell morphology (J). (K-O) FRT82B scrib¹ UAS-bsk^DN. Expressing Bsk^DN in scrib mutant clones increases clonal tissue size and mutant cells ectopically express CycE (K) and ectopically incorporate BrdU (L) posterior to the MF, although they arrest proliferation normally within the MF, and have aberrant cell morphology with many photoreceptor nuclei localized basally within the epithelium (M-O).