Journal of Neuroscience, Vol 6, 2968-2976, Copyright © 1986 by Society for Neuroscience
Differentiation and central projections of peripheral sensory cells with action-potential block in Drosophila mosaics
MG Burg and CF Wu
The ultrastructural differentiation and central projection of identified
bristle mechanosensory neurons were examined in Drosophila mutants lacking
action potentials. Two mutations, parats1 and napts, are known to block
axonal conduction in centrally located neurons at high temperatures. Their
effects on epithelial sensory cells, which are derived from imaginal disks
during pupation, have not been determined. Furthermore, the parats1 napts
double-mutant flies are lethal at all temperatures; thus the synergistic
effect of these mutations on neurons has not yet been studied. It is
possible to examine the above questions in genetic mosaics. By monitoring a
reflex response involving identified bristle sensory cells, we found that
the 2 mutations exert similar effects on these epithelial sensory cells as
seen in central neurons. This also indicates that the action potential
mechanisms in both epithelial sensory cells and central neurons are under
similar genetic control. The parats1 napts double-mutant sensory cells in
mosaics are nonfunctional at all temperatures, providing an opportunity to
examine, at the single cell level, the development of neurons with activity
block. Ultrastructural specializations typical of epithelial sensory cells
were found in the double-mutant cells. Cobalt backfilling experiments
showed that central projections of these nonfunctional sensory cells were
not altered, as compared with the active contralateral sensory cells.
Therefore, blockage of the action potential mechanism in individual sensory
cells has no effect on their pathfinding and arborization.