TCTN1

The protein is a component of the tectonic-like complex that localizes to the transition zone of primary cilia and acts as a barrier preventing diffusion of transmembrane proteins between cilia and plasma membranes, while also regulating Hedgehog signaling required for neural tube patterning. Mutations cause Joubert syndrome 13, a ciliopathy affecting the brain, kidneys, and other organ systems, inherited in an autosomal recessive pattern. The gene shows very high constraint against loss-of-function variants in the population.