Fig. 1. Dynactin is required to position photoreceptor cell bodies and nuclei in the developing third instar eye disc. Photoreceptor cell membranes are stained with anti-Chaoptin in A-G. (A) In wild type, photoreceptor cell bodies (as defined in this figure by the position of the nucleus) are precisely arranged in clusters in the apical region of the eye disc and project axons through the optic stalk (os) into the brain's optic lobe. (B) In Glued¹ mutants, many photoreceptor neuron cell bodies leave the apical region of the eye disc (arrowheads) and travel into the optic stalk (bracket) and brain (arrow). (C) Heterozygous cpb^M143 animals have a wild-type photoreceptor axon projection pattern, with photoreceptor cell bodies positioned in the eye disc. (D) In heterozygous cpb^M143 animals with homozygous cpb^M143/cpb^M143 patches in the visual system, many photoreceptor cell bodies leave the eye disc and enter the brain (arrows). (E) An independently generated cpb allele, cpb^F44, also causes photoreceptor cell bodies to enter the brain (arrows) in eye clones. (F) Photoreceptor mispositioning (arrows) is also observed in cpb^M143/Df(2L)E.2 animals rescued from early lethality by expression of Cpb from a genomic transgene [pYES-ß] (see text for details). (G) cpb^M143/Df(2L)E.2 animals rescued by ubiquitous expression of a wild-type Cpb cDNA have normal photoreceptor positioning. Photoreceptor nuclei are stained with anti-Elav in H-J. (H) In wild type, photoreceptor nuclei remain in the eye disc and do not enter the optic stalk. (I) Photoreceptor nuclei are mispositioned in cpb^M143 mosaic eye discs, with patches of eye tissue missing nuclei (arrows) and Elav-staining nuclei found in the optic stalk (arrowheads). (J) cpb^M143/Df(2L)E.2 animals rescued by ubiquitous expression of a Cpb cDNA have normal photoreceptor nuclear positioning.