CILK1 and cleft palate: By contrast, Cilk1-deficient cells exhibit excessive accumulation of Smo within the primary cilium even under unstimulated conditions, without corresponding activation of Hedgehog signaling.34 While loss-of-function mutations in primary cilia-related genes such as Ift88, Ofd1, and Kif3a cause severe developmental defects, including cleft palate and abnormal tooth patterning,37–39 the specific impact of Cilk1 on tooth development remains unclear.