skpA¹ mutant neuroblast clones result in mushroom body γ neurons retain many larval axons at 24 hours after puparium formation that are pruned in wild type. In wandering third instar larvae the dorsal and medial axons are projected normally but the axon branches are less dense than in wild type.

skpA¹ embryos develop normally and hatch at wild-type rates. Most mutant larvae die within four days of hatching and any surviving larvae grow slower than wild type and fail to pupate. In skpA¹ larvae, imaginal discs are either entirely absent or rudimentary. Virtually all cells in such rudimentary discs are undergoing apoptosis. The size of the CNS fails to significantly increase in skpA¹ mutants past 3 days after egg deposition (AED). This is caused by a reduction in cell proliferation, in the form of G1 arrest, rather than an increase in apoptosis. skpA¹ CNS cells often contain supernumerary centrosomes; as many as 17 have been observed in a single diploid cell. These appear to result from multiple rounds of centrosome duplication in the same cell cycle, as the centrosomes show no signs of fragmentation and cells appear to complete cytokinesis. The supernumerary centrosomes are able to nucleate microtubules and cluster into two poles to form a pseudo-bipolar spindle with the chromosomes positioned at a normal metaphase plate. This appears to form a compensatory mechanism that allows cells to progress to anaphase. As mitosis progresses, some of these centrosomes may become deactivated, as only a subset remain associated with the bulk of the spindle microtubules and some spindle poles are detached from any centrosome. In older skpA¹ larvae (from 3.5 days AED onwards), the ratio of cells in metaphase to anaphase is higher than wild type and those cells found in anaphase tend not to contain so many supernumerary centrosomes. This suggests that the cells containing supernumerary centrosomes become arrested in metaphase. The interphase nuclei of skpA¹ cells frequently show aberrant chromatin condensation. Clonal analysis shows that the supernumerary centrosomes, delayed cell cycle and abnormally condensed chromatin defects are all cell autonomous. Nuclei from the fat body and gut of skpA¹ larvae contain less DNA than wild type and undergo endoreduplication at a much lower rate than wild type. In contrast, levels of endoreduplication are not significantly different in skpA¹ larval salivary glands compared to wild type.