A Syntaxin1A protein mutation drives sleep reduction in Drosophila

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SUMMARY Syntaxin1A is a key component in the regulation of the vesicle fusion nanomachine and, together with VAMP/synaptobrevin and SNAP-25, forms the core of the SNARE complex, that is the molecular nanomachine regulating neurotransmitter release. Syntaxin1A is localized on the cytosolic face of the presynaptic membrane and with Munc-18-1 is thought to be the starting point for the SNARE complex assembly. 1 In flies, aspartic-to-arginine amino acid substitution at position 253 of the protein sequence reduces synaptic release by affecting the assembly of multiple SNARE complexes into a super-complex without interfering with the single complex formation per se. 2 In this study, we analyzed sleep behavior in flies expressing this mutated isoform of Syntaxin1A panneuronally. According to the synaptic homeostasis hypothesis, 3 the overall decrease of synaptic activity during the previous period of wakefulness should reduce the need for sleep. 4 We observed a reduction in the total amount of sleep in flies expressing the mutated isoform compared to controls. Moreover, the sleep pattern of the Syntaxina1A mutant flies was more fragmented compared to controls. Video-tracking analysis of free walking flies in an open-field arena showed that these changes were not caused by higher locomotor activity during the daytime relative to controls. Our results suggest that the widespread effect of Syntaxin1A mutation on synapses may lead to a dampening of the information load among neurons and, consequently, impact the regulation of sleep at the cellular level. Highlights The neurotransmitter release machinery modulates sleep in Drosophila A Syntaxin1A protein mutation causes fragmented night sleep Motor activity is not affected by the Syntaxin1A mutation Syntaxin1A could regulate the homeostasis of vesicle fusion and sleep In brief Frighetto et al., investigated the role of a single amino acid substitution in the Syntaxin1A protein in sleep and locomotor behavior. Following the pan-neuronal expression of this mutated Syntaxin1A, they found a specific reduction of sleep with locomotion remaining largely unaffected.

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