Phenotypic Assessment of Pathogenic Variants in GNAO1 and Response to Caffeine in C. elegans Models of the Disease

Abstract

De novo mutations affecting the G protein α o subunit (Gαo)-encoding gene (GNAO1) cause childhood-onset developmental delay, hyperkinetic movement disorders, and epilepsy. Recently, we established Caenorhabditis elegans as an informative experimental model for deciphering pathogenic mechanisms associated with GNAO1 defects and identifying new therapies. In this study, we generated two additional gene-edited strains that harbor pathogenic variants which affect residues Glu246 and Arg209—two mutational hotspots in Gαo. In line with previous findings, biallelic changes displayed a variable hypomorphic effect on Gαo-mediated signaling that led to the excessive release of neurotransmitters by different classes of neurons, which, in turn, caused hyperactive egg laying and locomotion. Of note, heterozygous variants showed a cell-specific dominant-negative behavior, which was strictly dependent on the affected residue. As with previously generated mutants (S47G and A221D), caffeine was effective in attenuating the hyperkinetic behavior of R209H and E246K animals, indicating that its efficacy is mutation-independent. Conversely, istradefylline, a selective adenosine A2A receptor antagonist, was effective in R209H animals but not in E246K worms, suggesting that caffeine acts through both adenosine receptor-dependent and receptor-independent mechanisms. Overall, our findings provide new insights into disease mechanisms and further support the potential efficacy of caffeine in controlling dyskinesia associated with pathogenic GNAO1 mutations.

Dyskinetic crisis in GNAO1-related disorders: clinical perspectives and management strategies

“…In terms of treatment, we have not discussed potential pharmacological interventions currently under investigation, such as the use of caffeine ( 40 ) and zinc acetate ( 41 ). Regarding caffeine, Di Rocco et al demonstrated its ability to attenuate hyperkinetic behavior in mutated R209H and E246K Caenorhabditis elegans .…”

AAV9-Mediated Intrastriatal Delivery ofGNAO1Reduces Hyperlocomotion inGnao1Heterozygous R209H Mutant Mice

“…These authors divide mutants into those having LOF and/or dominant negative (DN) activity. While in vitro data show a minimal phenotype for the R209H mutant, recent C. elegans behavioral testing showed that the R209H mutation has DN activity (Di Rocco et al, 2023;Knight et al, 2023). Like our mouse model, C. elegans R209H mutants display hyperactivity (Larrivee et al, 2020;Di Rocco et al, 2023).…”

Cortical neurons obtained from patient-derived iPSCs with GNAO1 p.G203R variant show altered differentiation and functional properties

“…Indeed, its expression increases during axonogenesis (14;15), and knockout mice show impaired neurogenesis (16), while Gnao1 deficient Drosophila models show defects during axon guidance (17). GNAO1 disease-linked pathogenic variants in mouse and worm models lead to a loss of function in Gα-mediated signaling with or without a dominant negative effect (18;19;20).…”

“…Despite currently available animal models, which include mouse, Drosophila and C. elegans (18;19;20;21;22;23;24), greatly contributing to a deeper understanding of this pathology, species-specific differences (e.g. neonatal lethality in p.G203R/+ mice; 22) make it hard to translate findings from animal models to humans.…”