Search

A null mutation of theDrosophila calcium/calmodulin-dependent protein kinase IIgene (CaMKII) was generated using homologous recombination. Null animals survive to larval and pupal stages due to a large maternal contribution ofCaMKIImRNA, 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 inCaMKII-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 inCaMKIImutants. 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-typeCaMKIIlocus, 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 ofCaMKIImRNA and a process that requires zygotic transcription ofCaMKIImRNA. 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.SIGNIFICANCE STATEMENTAs a regulator of synaptic development and plasticity, CaMKII has important roles in both normal and pathological function of the nervous system.CaMKIIshows high conservation betweenDrosophilaand humans, underscoring the usefulness ofDrosophilain modeling its function.Drosophila CaMKII-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 ofCaMKIImRNA 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 forDrosophila CaMKIImRNA variants.