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PLoS Genet

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PLoS Genetics

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Gain-of-function mutations in the human CaV2.1 gene CACNA1A cause familial hemiplegic migraine type 1 (FHM1). To characterize cellular problems potentially triggered by CaV2.1 gains of function, we engineered mutations encoding FHM1 amino-acid substitutions S218L (SL) and R192Q (RQ) into transgenes of Drosophila melanogaster CaV2/cacophony. We expressed the transgenes pan-neuronally. Phenotypes were mild for RQ-expressing animals. By contrast, single mutant SL- and complex allele RQ,SL-expressing animals showed overt phenotypes, including sharply decreased viability. By electrophysiology, SL- and RQ,SL-expressing neuromuscular junctions (NMJs) exhibited enhanced evoked discharges, supernumerary discharges, and an increase in the amplitudes and frequencies of spontaneous events. Some spontaneous events were gigantic (10-40 mV), multi-quantal events. Gigantic spontaneous events were eliminated by application of TTX-or by lowered or chelated Ca2+-suggesting that gigantic events were elicited by spontaneous nerve firing. A follow-up genetic approach revealed that some neuronal hyperexcitability phenotypes were reversed after knockdown or mutation of Drosophila homologs of phospholipase Cβ (PLCβ), IP3 receptor, or ryanodine receptor (RyR)-all factors known to mediate Ca2+ release from intracellular stores. Pharmacological inhibitors of intracellular Ca2+ store release produced similar effects. Interestingly, however, the decreased viability phenotype was not reversed by genetic impairment of intracellular Ca2+ release factors. On a cellular level, our data suggest inhibition of signaling that triggers intracellular Ca2+ release could counteract hyperexcitability induced by gains of CaV2.1 function.


Amino Acid Sequence, Animals, Calcium, Calcium Channels, N-Type, Cerebellar Ataxia, Drosophila melanogaster, Humans, Migraine Disorders, Mutation, Neuromuscular Junction, Neurons, Phenotype, Synapses, Synaptic Transmission, Transgenes


Extramural funding sources supporting this study and/or the authors include: National Institute of Neurological Disorders and Stroke Grants NS062738 and NS085164 to CAF (, Whitehall Foundation Grant 2014-08-03 to CAF (, National Science Foundation Grant 1557792 to CAF (, National Institutes of Health Predoctoral Training Grant T32GM008629 support to AMS ( (PI Daniel Eberl), and National Institutes of Health Predoctoral Training Grant T32NS007421 support to TDJ and CJY ( (PI Daniel T. Tranel). Intramural funding sources include: a University of Iowa Carver Medical Research Initiative Grant to CAF, and startup funds from the Department of Anatomy and Cell Biology at the University of Iowa Carver College of Medicine to CAF. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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PLoS Genet 14(8): e1007577.


© 2018 Brusich et al.

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