Examined in mosaics for effect on hindgut development. When cad activity is provided only maternally, the posterior gut appears essentially wild type. When cad is provided only zygotically, a hindgut tube is formed which can range from almost normal to reduced in length and twisted. When cad activity is completely lacking the hindgut, anal pads and eighth abdominal segment are almost entirely absent. Sections of a stage 13 embryo reveal numerous apoptotic cells in the region of the hindgut remnant. The byn-expressing ring of hindgut primordium draws together, but fails to invaginate. Germ band extension is retarded: by early stage 10 when the wild type germband is almost fully extended, the germband of cad deficient embryos is only 40% extended. The posterior midgut and Malpighian tubule primordia form and invaginate normally, though tubule elongation is incomplete.
Homozygous mutant germline clones were generated by γ ray induced mitotic recombination in cad3/Fs(2)M larvae. Mutant embryos have Malpighian tubules shorter than wild type and extreme segmentation defects. No cad protein is present but ct is expressed at normal levels demonstrating that cad and ct are independent of each other with respect to Malpighian tubule regulation.
