Expression of Arl2T30N.Scer\UAS driven by Scer\GAL4insc.PU results in a significant increase in neuroblast number in the third instar larval central brain; introduction of heterozygous Arl2Δ156/+ further enhances neuroblast overgrowth at 72hr (and even further at 84hr) after larval hatching at 29[o]C. Arl2Δ156/+ larvae that also have expression of Arl2T30N.Scer\UAS driven by Scer\GAL4insc.PU have a slightly extended larval stage and more than half of metaphase neuroblasts have shorter misoriented spindles (compared to wild type), with a small percentage dividing orthogonally. Larvae with Arl2T30N.Scer\UAS overexpressed by Scer\GAL4insc.PU also have spindle misorientation in around 25% of neuroblasts, and around 13% of neuroblasts divide symmetrically. Unlike wild type telophase neuroblasts (where daughter cell sizes are distinct, with a NB/GMC diameter ratio of around 2), larvae with Arl2T30N.Scer\UAS overexpressed by Scer\GAL4insc.PU have a reduced ratio (around 1.65); introduction of Arl2Δ156/+ further reduces the ratio (around 1.5).
Arl2T30N.Scer\UAS clones have extra neuroblasts in both type I (Scer\GAL4ase.neuro) and II (Scer\GAL4wor.PA and Scer\GAL80ase.PN) neuroblast lineages, compared to a single neuroblast in control clones (third instar larval central brain).
After treatment on ice (to depolymerize microtubules and disrupt mitotic spindles), in larvae with Arl2T30N.Scer\UAS driven by Scer\GAL4insc.PU around 40% of metaphase neuroblasts reassembled less microtubule mass after 30 seconds recovery and only 46% form mitotic spindles (that are shorter and more narrow), compared to wild type.