Single cell class IV dendrite arborisation (da) neuron clones that are homozygous for esc21 show a range of dendritic defects in the third instar larva. Homozygous class IV ddaC clones show a significant reduction in dendrite branching and total dendritic length compared to controls.
Homozygotes can survive through larval stages and often into adulthood.
Dendrites of class IV dendrite arborisation (da) neurons are indistinguishable from wild-type controls in homozygotes throughout embryogenesis and early larval stages. However, beginning at 48 hours after egg laying (AEL), defects in class IV dendrites become evident in homozygotes. By 96 hours AEL there is a significant reduction both in the number of terminal dendritic branches and in total dendritic length in the homozygotes. In some severe cases (approximately 10% of neurons sampled), there is a complete loss over major regions of the dendritic field. Analysis of dendrite development between 72 and 96 hours AEL shows that homozygous class IV dendrites show extensive growth during this period, as occurs in controls, but in the mutants, some major dendritic trunks show signs of severing (which is never seen in controls). By 96 hours AEL, the severed dendrites are almost completely eliminated in the mutants. Mutant dendrites show a greater number and apparent rate of retraction events than controls.
Class IV da neurons show no sign of cell death in mutant third instar larvae and they persist through metamorphosis and into adulthood.
Class IV da neurons enter the central nervous system at the appropriate position in mutant larvae and the overall morphology of the neurons in the central nerve cord is indistinguishable from that of controls.
Heterozygous males do not have ectopic sex combs on the second or third legs.
Heterozygous males do not have ectopic sex combs on the second and third legs.