Synaptic homeostasis is consolidated by the cell fate gene gooseberry, a Drosophila pax3/7 homolog.
In a large-scale screening effort, we identified the gene gooseberry (gsb) as being necessary for synaptic homeostasis at the Drosophila neuromuscular junction. The gsb gene encodes a pair-rule transcription factor that participates in embryonic neuronal cell fate specification. Here, we define a new postembryonic role for gooseberry. We show that gsb becomes widely expressed in the postembryonic CNS, including within mature motoneurons. Loss of gsb does not alter neuromuscular growth, morphology, or the distribution of essential synaptic proteins. However, gsb function is required postembryonically for the sustained expression of synaptic homeostasis. In GluRIIA mutant animals, miniature EPSP (mEPSP) amplitudes are significantly decreased, and there is a compensatory homeostatic increase in presynaptic release that restores normal muscle excitation. Loss of gsb significantly impairs the homeostatic increase in presynaptic release in the GluRIIA mutant. Interestingly, gsb is not required for the rapid induction of synaptic homeostasis. Furthermore, gsb seems to be specifically involved in the mechanisms responsible for a homeostatic increase in presynaptic release, since it is not required for the homeostatic decrease in presynaptic release observed following an increase in mEPSP amplitude. Finally, Gsb has been shown to antagonize Wingless signaling during embryonic fate specification, and we present initial evidence that this activity is conserved during synaptic homeostasis. Thus, we have identified a gene (gsb) that distinguishes between rapid induction versus sustained expression of synaptic homeostasis and distinguishes between the mechanisms responsible for homeostatic increase versus decrease in synaptic vesicle release.
Marie
Bruno
B
Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California 94158-2822, USA.
Pym
Edward
E
Bergquist
Sharon
S
Davis
Graeme W
GW
D000818:Animals; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D034281:Dynamins / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D004625:Embryo, Nonmammalian; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006706:Homeostasis / Q000235:genetics*; D008954:Models, Biological; D009046:Motor Neurons / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D009469:Neuromuscular Junction / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference / Q000502:physiology; D018091:Receptors, AMPA / Q000502:physiology; D031965:Ribes / Q000235:genetics*; D016704:Synapsins / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
C510146:BRP protein, Drosophila; D029721:Drosophila Proteins; D018091:Receptors, AMPA; D016704:Synapsins; D025521:Tumor Suppressor Proteins; C070350:dlg1 protein, Drosophila; D049452:Green Fluorescent Proteins; D001616:beta-Galactosidase; D034281:Dynamins; C104722:glutamate receptor ionotropic, AMPA 2