Induced disruption in the connectivity of an identified neuron in the Drosophila ts mutant shibire.

Temperature-sensitive mutants permit the selective expression of mutant genotype. The Drosophila ts mutant shibire (shi) is paralytic at 30 degrees C; the probable primary effect of the mutation is disruption of membrane recycling. In studying the development of the giant fiber (GF) pathway during the pupal period, we find that shi flies exposed to heat pulse during early pupal states exhibit perturbation in the development of an identified neuron that links giant fibers to motoneurons of indirect flight muscles. Concomitantly, latency in activation of these muscles by the giant fiber pathway is significantly increased. Flies exposed to heat pulse during the late pupal period remain similar to control shi and wildtype flies in giant fiber pathway anatomy and muscle latency. Thus, the critical period of development of an identified neuron in a known motor pathway can be defined by its period of sensitivity to the shi defect. The time-dependent defect is apparently specific for cells that are at a developmental stage that is greatly dependent on membrane recycling processes. Use of this mutant will allow us to investigate the possible role of membrane recycling in development and to establish critical periods of neuronal development.