Methods to Assess Neuronal Primary Cilia Electrochemical Signaling

Primary cilia are polymodal sensory organelles which project from the apical side of polarized cells. They are found in all brain hemispheres but are most pronounced in neurons, which comprise the granular layers of the hippocampus and cerebellum. Pathogenic variants in genes which encode primary cilia components are responsible for neuronal ciliopathies—a group of central nervous system disorders characterized by neurodevelopmental conditions such as intellectual disability, seizure, ataxia, and sensory deficits. In the hippocampus, neuronal primary cilia form chemical synapses with axons and their membranes are populated with unique sets of ion channels and G protein-coupled receptors (GPCRs). Primary cilia are small and privileged compartments that are challenging organelles to study. In detail, we describe cilia electrophysiology methods and the use of cilia-specific fluorescent sensors to assay neuronal polycystin channel function and serotonergic receptor signaling, respectively. These tools allow researchers to assay calcium, cAMP and channel-related signaling pathways in isolated neurons in real-time and in semi-quantitative terms, while enhancing our understanding of this understudied organelle and its dysregulation in ciliopathy disease states.