<i>Caenorhabditis elegans</i> models of alternating hemiplegia of childhood have dominant neuromuscular junction defects

Dominant missense mutations in ATP1A3, encoding ATPase Na+/K+-transporting subunit alpha3, can cause the neurological disorder alternating hemiplegia of childhood (AHC), but how these mutations lead to AHC remains unclear. Here, we established the first Caenorhabditis elegans AHC models by introducing AHC-causing ATP1A3 mutations (i.e. D801N, E815K, L839P and G947R substitutions) into the orthologous gene eat-6 by using CRISPR/Cas9. Homozygous C. elegans AHC model animals have recessive developmental defects. Heterozygous AHC model animals have dominant defects in neuromuscular junction (NMJ) function that are inconsistent with haploinsufficiency and dominant sleep or arousal defects. Previous work in a Drosophila G755S AHC model found that loss of a K+-dependent, Na+/Ca²+ exchanger exacerbated neuronal defects. We introduced a loss-of-function allele of the orthologous C. elegans ncx-4 gene into C. elegans AHC models. Loss of ncx-4 function mutation did not consistently alter C. elegans AHC model defects across alleles. Our results established novel C. elegans models of AHC with robust phenotypes, demonstrating that AHC-causing ATP1A3 variants disrupt NMJ function, and providing proof-of-concept for discovering cross-species modifiers of AHC-related phenotypes.