Contractile ring dynamics in stiGS9053/Df(3L)iro-2 mutant neuroblasts are similar to controls, albeit less uniform, indicating that the defects in contractile ring organization observed in the absence of sti occur after and not during cleavage furrow ingression.
Stage 16 stiGS9053/Df(3L)iro-2 embryos have a modestly disrupted peripheral nervous system (PNS) with some disorganisation of clusters and defects in axonal projections. There is also a reduction in the numbers of PNS neurons in these embryos, and concomitant appearance of binucleate neurons (about 15% of total neurons are binucleate). About 1/4 of cells in the brains of third instar stiGS9053/Df(3L)iro-2 larvae have massively enlarged nuclei. Chromosome preparations from these brains show tetraploid metaphase figures and some massively hyperploid cells. As chromosomes seem to separate normally in all except the most polyploid of cells, the defect appears to be in cytokinesis, rather than some other aspect of mitosis. These larvae also exhibit a variable reduction in imaginal disc size. This is associated with an increase in apoptosis in the imaginal discs and a decrease in numbers of cells expressing mitotic markers.