Figure 1.

Mbs mutant photoreceptors move basally and into the optic stalk. (A-C) Eye discs with Mbs^T666 clones stained with anti-Elav to label photoreceptor nuclei (A, red in B, brown in C). Wild-type tissue is marked with arm-lacZ, stained with anti-β-galactosidase in green (B) or X-gal in blue (C). Posterior is to the right. Many mutant cells are lost from the apical layer, and some Elav-positive nuclei are present in the optic stalk (arrow in C). (D and E) show cross sections of the discs in A and B, with apical up. Wild-type nuclei are close to the apical surface, but many mutant nuclei are found close to the basal surface. (F) Cross-section of an eye disc with Mbs^T666 mutant cells positively marked with CD8-GFP (green). Elav is stained in red. The entire membrane of Mbs mutant cells seems to be located basally within the disc. (G and H) Eye discs with Mbs^T666 clones stained with anti-phosphotyrosine (G, red in H) and with anti-β-galactosidase, marking wild-type tissue, in green in H. Apical constriction in the furrow is slightly reduced in the mutant tissue, and no ectopic constriction is visible in posterior regions. (I-L) Cross-sections of discs with Mbs^T541 clones stained with anti-E-cadherin (I, blue in J), anti-Elav (red in J), anti-Patj (K, red in L), and anti-β-galactosidase to mark wild-type tissue (green in J and L). E-cadherin and Patj are still expressed in mutant tissue, but at a more basal level than in wild-type tissue; staining is apical to mislocalized nuclei (J).