The daily sleep cycle in humans and other mammals is driven by a complex circuit within which GABAergic sleep-promoting neurons oppose arousal systems. The latter includes the circadian system, aminergic/cholinergic systems as well as neurons secreting the peptide orexin/hypocretin, which contribute to sharp behavioral transitions (Lu and Greco, 2006). Drosophila sleep has recently been shown also to be controlled by GABAergic inputs, which act on unknown cells expressing the Rdl GABAA receptor (Agosto et al., 2008). We identify here the relevant Rdl-containing cells as a subset of the well-studied Drosophila circadian clock neurons, the PDF-expressing small and large ventral lateral neurons (LNvs). LNv activity regulates the total amount of sleep as well as the rate of sleep onset, and both large and small LNvs are part of the sleep circuit. Flies mutant for either the pdf gene or its receptor are hypersomnolent, and PDF acts on the LNvs themselves to control sleep. These features of the Drosophila sleep circuit, GABAergic control of sleep onset and maintenance as well as peptidergic control of arousal, support the idea that features of sleep circuit architecture as well as the mechanisms governing the behavioral transitions between sleep and wake are conserved between mammals and insects.

Genetic causes for disturbances of locomotor behavior can be due to muscle, peripheral neuron, or central nervous system pathologies. The Drosophila melanogaster homolog of human CASK (also known as caki or camguk) is a molecular scaffold that has been postulated to have roles in both locomotion and plasticity. These conclusions are based on studies using overlapping

A null mutation of the gene () was generated using homologous recombination. Null animals survive to larval and pupal stages due to a large maternal contribution of mRNA, which consists of a short 3'-untranslated region (UTR) form lacking regulatory elements that guide local translation. The selective loss of the long 3'UTR mRNA in-null larvae allows us to test its role in plasticity. Development and evoked function of the larval neuromuscular junction are surprisingly normal, but the resting rate of miniature excitatory junctional potentials (mEJPs) is significantly lower in mutants. Mutants also lack the ability to increase mEJP rate in response to spaced depolarization, a type of activity-dependent plasticity shown to require both transcription and translation. Consistent with this, overexpression of miR-289 in wild-type animals blocks plasticity of spontaneous release. In addition to the defects in regulation of mEJP rate, CaMKII protein is largely lost from synapses in the mutant. All phenotypes are non-sex-specific and rescued by a fosmid containing the entire wild-type locus, but only viability and CaMKII localization are rescued by genomic fosmids lacking the long 3'UTR. This suggests that synaptic CaMKII accumulates by two distinct mechanisms: local synthesis requiring the long 3'UTR form of mRNA and a process that requires zygotic transcription of mRNA. The origin of synaptic CaMKII also dictates its functionality. Locally translated CaMKII has a privileged role in regulation of spontaneous release, which cannot be fulfilled by synaptic CaMKII from the other pool. As a regulator of synaptic development and plasticity, CaMKII has important roles in both normal and pathological function of the nervous system. shows high conservation between and humans, underscoring the usefulness of in modeling its function.-null mutants remain viable throughout development, enabling morphological and electrophysiological characterization. Although the structure of the synapse is normal, maternally contributed CaMKII does not localize to synapses. Zygotic production of mRNA with a long 3'-untranslated region is necessary for modulating spontaneous neurotransmission in an activity-dependent manner, but not for viability. These data argue that regulation of CaMKII localization and levels by local transcriptional processes is conserved. This is the first demonstration of distinct functions for mRNA variants.

On page 800 of our paper, the intracellular solution used for measurements of LTP is erroneously described as containing KMeS0 3 . In reality, a cesium-based (CsMeSO 3 ) intracellular solution was actually used for these voltage-clamp recordings.

Drosophila ether-à-go-go ( eag) is the founding member of a large family of voltage-gated K channels, the KCNH family, which includes Kv10, 11, and 12. Concurrent binding of calcium/calmodulin (Ca/CaM) to NH- and COOH-terminal sites inhibits mammalian EAG1 channels at submicromolar Ca concentrations, likely by causing pore constriction. Although the Drosophila EAG channel was believed to be Ca-insensitive (Schönherr R, Löber K, Heinemann SH. EMBO J 19: 3263-3271, 2000.), both the NH2- and COOH-terminal sites are conserved. In this study we show that Drosophila EAG is inhibited by high Ca concentrations that are only present at plasma membrane Ca channel microdomains. To test the role of this regulation in vivo, we engineered mutations that block CaM-binding to the major COOH-terminal site of the endogenous eag locus, disrupting Ca-dependent inhibition. eag CaMBD mutants have reduced evoked release from larval motor neuron presynaptic terminals and show decreased Ca influx in stimulated adult projection neuron presynaptic terminals, consistent with an increase in K conductance. These results are predicted by a conductance-based multicompartment model of the presynaptic terminal in which some fraction of EAG is localized to the Ca channel microdomains that control neurotransmitter release. The reduction of release in the larval neuromuscular junction drives a compensatory increase in motor neuron somatic excitability. This misregulation of synaptic and somatic excitability has consequences for systems-level processes and leads to defects in associative memory formation in adults. NEW & NOTEWORTHY Regulation of excitability is critical to tuning the nervous system for complex behaviors. We demonstrate in this article that the EAG family of voltage-gated K channels exhibit conserved gating by Ca/CaM. Disruption of this inhibition in Drosophila results in decreased evoked neurotransmitter release due to truncated Ca influx in presynaptic terminals. In adults, disrupted Ca dynamics cripples memory formation. These data demonstrate that the biophysical details of channels have important implications for cell function and behavior.