Fusogen-mediated neuron−neuron fusion disrupts neural circuit connectivity and alters animal behavior

Significance Ramón y Cajal’s neuron doctrine, which states that neurons are individual cells that do not share any membrane or cytoplasmic continuity between them, has underpinned our view of modern neuroscience. However, there is considerable evidence that fusogens, specialized proteins essential and sufficient for the fusion of cells in other tissues, are expressed in the nervous system of several species in response to viral infection, stress conditions, and neurological disease. By manipulating the expression of fusogens in the chemosensory neurons of Caenorhabditis elegans , our results provide conclusive evidence that deregulation of fusogen expression causes neuronal fusion and can have deleterious effects on neural circuitry and behavioral outputs, revealing a possible novel underlying cause of neurological disorders.