Down-regulation of robo through targeted expression of commScer\UAS.cKa under the control of Scer\GAL4eve.CQ2 induces ectopic dendritic innervation of the midline neuropile (ith 100% penetrance for MN-LL1 and 62.5% penetrance for MN-DA3) with a concomitant reduction of the lateral arbor.
The antennal lobes of commScer\UAS.cKa; Scer\GAL4SG18.1 flies have a disorganized pattern of glomeruli, and while the antennal commissure is present, its axons are loosely fasciculated.
When expression is driven by Scer\GAL412.1 the cd sensory neuron projections are shifted from the intermediate to the medial longitudinal fascicles. In approximately 50% of cases, cd sensory neuron projections cross the midline.
Longitudinal tracts look normal in embryos expressing commScer\UAS.cKa under the control of Scer\GAL4btl.PS. 17% of ganglionic branches cross the midline in these embryos, 14% turn anteriorly at the midline and 15% stall prematurely.
Expression of commScer\UAS.cKa under the regulation of Scer\GAL4A307, in the giant fiber system results in the collapse of the giant fiber axons at the midline, with the axons often wrapping around each other. The latency (a measure of synaptic function) of these axons is unaffected. Expression of commScer\UAS.cKa in the tergotrochanteral motor neurons, under the control of Scer\GAL4shakB.lethal.4.1 has no effect on the dendritic projection or the function of the synapse.
Expression of commScer\UAS.cKa under the control of Scer\GAL4ap-md52 causes ap-expressing neurons to cross the midline, in contrast to wild type. Thoracic-specific ap-expressing neurons cross in the posterior commissure (PC), whereas other ap-expressing neurons cross in the anterior commissure (AC).
Axons freely cross and recross the midline in the central nervous system (CNS) of embryos expressing commScer\UAS.cKa under the control of Scer\GAL4sca-537.4. Increasing the copy number of commScer\UAS.cKa results in a more severe phenotype, the strongest phenotype has axons entering the midline but not leaving it, leading to a collapse of the CNS scaffold onto the midline.
More axons than normal cross the midline in embryos expressing commScer\UAS.cKa under the control of Scer\GAL4sca-537.4. The pCC pathway crosses the midline, joins with its contralateral pathway and forms circles around the midline. The midline glia are present and migrate to their normal position. The phenotype caused by commScer\UAS.cKa expressed under the control of Scer\GAL4sca-537.4 is dosage sensitive.