Fig. 4. Genetics of differentiation and Hairy downregulation. Panels A-H show Senseless expression (green) and Hairy expression (blue) in various genotypes. Clones of mutant cells are revealed by the absence of Ci155 (red; panels A-F), or absence of the lacZ marker gene (red; panels G,H). In E-H, outlines of clone boundaries have been overlaid on the Hairy channel to help assess autonomy. Because of variations in reagents and procedures over time (see Materials and methods), labeling intensities can only rigorously be compared between cells of different genotypes within the same preparation. (A) Differentiation is delayed in Mad ci-mutant cells. (B) Mad ci-mutant cells maintain Hairy expression longer, except where they are close to wild-type cells. If wild-type cells are nearby, Hairy expression is lost close to the normal time (e.g. arrow). (C) tkv ci-mutant cells do not differentiate. (D) tkv ci-mutant cells maintain Hairy expression longer, except where they are close to wild-type cells. If wild-type cells are nearby, Hairy is lost close to the normal time (e.g. arrow). In addition, Hairy levels are reproducibly lower in mutant cells than in wild type. (E) Mad Su(H) ci-mutant cells do not differentiate. Mutant cells maintain Hairy expression indefinitely, even where they are neighboring wild-type cells. (F) Differentiation of Su(H) ci-mutant cells is slightly delayed. There is an excess of Senseless-expressing R8 cells, though not so extreme as in Su(H)-mutant clones (compare with panel G). Su(H) ci-mutant cells maintain Hairy expression indefinitely, even where they are neighboring wild-type cells. Note the overlap between Senseless-expressing and Hairy-expressing regions. (G) Su(H)-mutant cells differentiate at or before the normal time and are strongly neurogenic (Li and Baker, 2001). Weak Hairy expression is maintained after the normal time but it is soon lost. There is limited overlap between Senseless-expressing and Hairy-expressing regions. (H) Mad Su(H)-mutant cells differentiate at or before the normal time and are strongly neurogenic. Hairy expression is maintained after the normal time but it is soon lost. There is limited overlap between Senseless-expressing and Hairy-expressing regions.