Unlike in wild type, where dendrites cluster around the photoreceptor axons in their cognate column, babo⁹ mutant Tm20 neuron clones extend their neurons laterally in medulla layer M3a and invade neighboring columns. Furthermore, the mutant dendritic branches in the internal medulla M8 layer exhibit a similar overextension phenotype. The mutant Tm20s' axons are correctly targeted to the fifth layer of the lobula.

The dendritic terminating frequency of babo⁹ mutant Tm20 neurons is significantly reduced compared to wild type, although the dendritic branching frequency was only mildly affected. The axonal locations and dendrite planar projection pattern of babo⁹ mutant Tm20 are comparable to those of wild type, while the percentage of dendritic branches terminating in medulla layer M3a is increased by approximately 12%.

babo⁹ mutant Tm20 neurons form aberrant synapses with neighbouring photoreceptors. babo⁹ mutant Tm20 dendrites contact the presynaptic sites of both cognate and neighboring rhabdomere R8s.

The dendrites of babo⁹ mutant Dm8 neuron clones occupy a larger space than wild type ones. babo⁹ mutant Dm8 dendrites occupy significantly more dendritic field units than the wild type ones. As in wild type, babo⁹ mutant Dm8 neurons are routed to medulla layer M6.

Homozygous clones in the larval optic lobe and central brain contain 30-50% fewer cells than wild-type control clones in similar positions.

A significant proportion of babo⁹ mosaic flies exhibit mutant R7 photoreceptor cells and do not phototax to visible light.

R7 photoreceptor clones homozygous for babo⁹ invade neighboring columns occupied by wild-type R7s.

babo⁹ mutant R7 photoreceptor cells target correctly at 40 hours after puparium formation (APF), but extend laterally into neighboring columns at 50 hours APF.

babo⁹ mutant dorsal cluster neuron clones display various anomalies. These defects include arrest of most axons at the protocerebrum---optic lobe junction, overextension of neurites from the ipsilateral lobular complex, ectopic projections in the central brain and aberrant fasciculation of processes. There is a delay in the initial development of babo⁹ mutant dorsal cluster neurons compared to wild-type neurons. There are no detectable babo⁹ dorsal cluster clones until 3 days after larval hatching, which is roughly one-half day late compared with wild-type neurons. babo⁹ clones undergo minimal morphogenesis during larval development and remain tiny. Misrouting of mutant neurites becomes evident by 24h APF. The mutant clones contain similar numbers of cell bodies to wild-type clones, suggesting that development of dorsal cluster neurons is delayed but not blocked. Single cell/two cell babo⁹ clones of dorsal cluster neurons fail to extend axons into the contralateral optic lobe and their initial trajectories can be kinky compared to wild-type clones. MARCM babo⁹ clones of ellipsoid body neurons are slow in initial morphogenesis. babo⁹ axons correctly navigate and initiate arborization inside the ellipsoid body but their arbors fail to converge properly at the midline, resulting in a deformed ellipsoid body ring. babo⁹ γ neuron clones show mushroom body defects.

When single cell mutant clones in adult γ neurons, abnormal projection patterns are seen. Mutant neurons possess two major axonal branches that project perpendicularly away from each other, as in larval γ projections. Wild-type patterns of dendrites and axons are seen in mutant γ neurons before puparium formation. However pruning of larval dendrites and axons does not happen to mutant neurons during early metamorphosis, persisting to adult stages. Mutant neuroblasts clones lack the prominent γ-lobe and instead possess the retained larval dorsal/ventral lobes in addition to the weak core α/β lobes.

Single cell mutant γ neuron MARCM clones in the mushroom body have abnormal dendritic arborisation patterns; 50% of mutant neurons have only one primary branch (wild-type neurons have 3 or more primary dendritic branches). Most mutant dendrites appear to originate within a narrow circumferential region above the equator of the adult calyx (whereas in wild type, secondary branching points are distributed widely over the primary neurites). In the wild-type, dendrites usually elaborate in a non-overlapping manner and their individual terminal branches occupy discrete territories. Wild-type dendrites from different clonal units are widely distributed and outline the entire calyx. In contrast, mutant dendrites derived from different clonal units often become extensively intermingled and occupy a relatively restricted space close to the central anterior surface of the calyx, forming an ectopic fourfold dendritic domain.

babo⁹ has adult mushroom body gamma-lobe | somatic clone phenotype, non-suppressible by Scer\GAL4^Tab2-201Y/EcR^A.UAS

babo⁹ has adult mushroom body gamma-lobe | somatic clone phenotype, non-suppressible by Scer\GAL4^Tab2-201Y/EcR^B2.UAS