To reduce computational cost and improve detection of small defects, a useful approach is to divide the waveform tomography procedure into two steps: first, a low-frequency model-building step aimed at recovering background structure, and second, a high-frequency imaging step targeting defects.
Of interest is that the degree of activation achieved with elav-Gal4>UAS-Rheb, a level that did not produce lethality, did result in discernable axon targeting defects in the visual system.
A mutagenesis and biochemical study performed on E.coli Ffh revealed a subset of mutations that abrogates the effect of the SRP RNA and results in targeting defects in vivo [31].
Sequestration of membrane sterols clearly leads to abnormalities in ORN axon outgrowth, glomerulus formation, and migration of neuropil glia, and the abnormal patterns of MFas II-positive ORN axons visualized in MβCD-treated preparations hinted at the possibility of targeting defects (Fig. 8).
However, previous mutant analyses described R7 targeting defects into layers that form after P + 30%.
Mutants of Pabp2 show pathfinding and targeting defects in the larval neuromuscular junction [ 81].
Triplett and colleagues show no targeting defects in the LGN of Isl2-EphA3 animals (Triplett et al. 2009).
Our live imaging data reveal that CadN-deficient R7 axons have no initial targeting defects and CadN does not function as a target layer-specific cue.
Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers.
