Functional classification of disorder variants in uncovers conserved and cell-specific mechanisms of dysfunction.

Heterotrimeric G proteins transduce signals from G protein coupled receptors, which mediate key aspects of neuronal development and function. Mutations in the gene, which encodes Gαi1, cause a disorder characterized by developmental delay, intellectual disability, hypotonia, and epilepsy. However, the mechanistic basis for this disorder remains unknown. Here, we show that is required for ciliogenesis in human cells and use as a whole-organism model to determine the functional impact of seven disorder patient variants. Using CRISPR-Cas9 editing in combination with robust cellular (cilia morphology) and behavioral (chemotaxis) assays, we find that , , , and orthologous variants impact both cilia assembly and function in AWC neurons, and have no impact on either phenotype, and exerts neuron-specific effects on cilia-dependent sensory behaviors. Finally, we validate in human ciliated cell lines that , , and variants disrupt ciliary localization of the encoded human Gαi1 proteins similarly to their corresponding orthologous substitutions in the ODR-3 , , and ). Overall, our findings determine the effects of orthologous variants and contribute to mechanistic understanding of disorder pathogenesis as well as neuron-specific roles of ODR-3 in sensory biology.