posterior scutellar bristle & mechanosensory neuron
posterior scutellar bristle & mechanosensory neuron (with Dscam121)
posterior scutellar bristle & mechanosensory neuron (with Dscam1ΔR265)
95% of DscamΔR272 flies exhibit defects in axonal branching posterior Scutellar (pSc) neurons. More than half of these flies show multiple errors along the pSc axon. For example, the main primary extension is misrouted across the midline contralaterally in 13% of mutants. This extension fails to branch contralaterally in 10% of mutants, or extends along the midline and forms several small ectopic branches (10% of mutants) or is completely truncated and fails to innervate the metathoracic region (6%). DscamΔR272/Dscam21 transheterozygotes show similar defects to DscamΔR272 homozygotes, while the penetrance of defects is lower in DscamΔR265/DscamΔR272 transheterozygotes.
Analysis of the exon 4 sequences confirms the absence of alternative exons 4.4 to 4.8 in transcripts from DscamΔR272 alleles and shows a compensatory upregulation of the remaining alternative exon 4 sequences.