Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 113, Issue 33, Pages E4895-E4903Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1605216113
Keywords
sudden unexpected death in epilepsy; SUDEP; catecholaminergic polymorphic ventricular tachycardia; CPVT; ryanodine receptor
Categories
Funding
- NIH Center for SUDEP Research Grants [NS090340, NS29709]
- NIH [HL089598, HL091947, HL117641, HL129570]
- American Heart Association Grants [13EIA14560061, 14POST20130031]
- Blue Bird Circle Foundation
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Cardiorespiratory failure is the most common cause of sudden unexplained death in epilepsy (SUDEP). Genetic autopsies have detected leaky gain-of-function mutations in the ryanodine receptor-2 (RyR2) gene in both SUDEP and sudden cardiac death cases linked to catecholaminergic polymorphic ventricular tachycardia that feature lethal cardiac arrhythmias without structural abnormality. Here we find that a human leaky RyR2 mutation, R176Q (RQ), alters neurotransmitter release probability in mice and significantly lowers the threshold for spreading depolarization (SD) in dorsal medulla, leading to cardiorespiratory collapse. Rare episodes of sinus bradycardia, spontaneous seizure, and sudden death were detected in RQ/+ mutant mice in vivo; however, when provoked, cortical seizures frequently led to apneas, brainstem SD, cardiorespiratory failure, and death. In vitro studies revealed that the RQ mutation selectively strengthened excitatory, but not inhibitory, synapses and facilitated SD in both the neocortex as well as brainstem dorsal medulla autonomic microcircuits. These data link defects in neuronal intracellular calcium homeostasis to the vulnerability of central autonomic brainstem pathways to hypoxic stress and implicate brainstem SD as a previously unrecognized site and mechanism contributing to premature death in individuals with leaky RYR2 mutations.
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