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straightjacket is required for the synaptic stabilization of cacophony, a voltage-gated calcium channel
1 subunit
Correspondence to H. Bellen: hbellen{at}bcm.tmc.edu
In a screen to identify genes involved in synaptic function, we isolated mutations in Drosophila melanogaster straightjacket (stj), an
2
subunit of the voltage-gated calcium channel. stj mutant photoreceptors develop normal synaptic connections but display reduced "on–off" transients in electroretinogram recordings, indicating a failure to evoke postsynaptic responses and, thus, a defect in neurotransmission. stj is expressed in neurons but excluded from glia. Mutants exhibit endogenous seizure-like activity, indicating altered neuronal excitability. However, at the synaptic level, stj larval neuromuscular junctions exhibit approximately fourfold reduction in synaptic release compared with controls stemming from a reduced release probability at these synapses. These defects likely stem from destabilization of Cacophony (Cac), the primary presynaptic
1 subunit in D. melanogaster. Interestingly, neuronal overexpression of cac partially rescues the viability and physiological defects in stj mutants, indicating a role for the
2
Ca2+ channel subunit in mediating the proper localization of an
1 subunit at synapses.
Abbreviations used in this paper: Brp, Bruchpilot; Cac, Cacophony; CPG, central pattern generator; EJP, excitatory junctional potential; ERG, electroretinogram; mEJP, miniature EJP; NMJ, neuromuscular junction; PR, photoreceptor; SSR, subsynaptic reticulum; stj, straightjacket; TEM, transmission electron microscopy; TTX, tetrodotoxin; VGCC, voltage-gated calcium channel; VNC, ventral nerve cord; VWA, von Willebrand factor A.
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