The midline glia are specialized, nonneuronal cells at the midline of the Drosophila central nervous system (CNS). During development, the midline glia provide guidance cues for extending axons. At... Show moreThe midline glia are specialized, nonneuronal cells at the midline of the Drosophila central nervous system (CNS). During development, the midline glia provide guidance cues for extending axons. At the same time, they migrate and help separate the two axon commissures. They then wrap around and ensheath the commissural axons. In many segments, a few of the glia do not enwrap the axons, and these cells die. The wrapper gene encodes a novel member of the immunoglobulin (Ig) superfamily. Wrapper protein is expressed specifically on the surface of midline glia. In wrapper mutant embryos, the midline glia express their normal guidance cues and migrate normally. However, they do not ensheath the commissural axons, and as a result, the glia die. In the absence of Wrapper, the two axon commissures are not properly separated. Show less
Postsynaptic sensitivity to glutamate was genetically manipulated at the Drosophila neuromuscular junction (NMJ) to test whether postsynaptic activity can regulate presynaptic function during... Show morePostsynaptic sensitivity to glutamate was genetically manipulated at the Drosophila neuromuscular junction (NMJ) to test whether postsynaptic activity can regulate presynaptic function during development. We cloned the gene encoding a second muscle-specific glutamate receptor, DGluRIIB, which is closely related to the previously identified DGluRIIA and located adjacent to it in the genome. Mutations that eliminate DGluRIIA (but not DGluRIIB) or transgenic constructs that increase DGluRIIA expression were generated. When DGluRIIA is missing, the response of the muscle to a single vesicle of transmitter is substantially de- creased. However, the responseof the muscle to nerve stimulation is normal because quantal content is significantly increased. Thus, a decrease in postsynaptic receptors leads to an increase in presynaptic transmitter release, indicating that postsynaptic activity controls a retrograde signal that regulates presynaptic function. Show less
