SignificanceImbalance between neural cell proliferation and neuronal differentiation during development can result in pediatric cancer or neurodevelopmental disorders. Thus, understanding the mechanisms that control this transition is paramount for preventing and treating these conditions. Here we show that the recruitment of a calcium-dependent mechanism in the developing neural cell primary cilium, converts the developmental signal Sonic hedgehog from proliferative into differentiating. The identified mechanism may become a target for devising therapeutics for brain tumors.