Has an essential role in ciliogenesis, particularly in neuronal and retinal progenitor cells (PubMed:24797473). Phosphorylates KIF3A (PubMed:24797473). Involved in the control of ciliary length (PubMed:24853502). Regulates the ciliary localization of SHH pathway components as well as the localization of IFT components at ciliary tips (PubMed:24797473, PubMed:24853502). May play a role in cardiac development (By similarity). Regulates intraflagellar transport (IFT) speed and negatively regulates cilium length in a cAMP and mTORC1 signaling -dependent manner and this regulation requires its kinase activity (PubMed:25243405). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Also found at the ciliary tip (PubMed:24797473). Predominant nuclear localization has been observed with a N-terminally GFP-tagged construct in transfected COS-7 cells (PubMed:15988018). Highly expressed in colon and lung, lower levels present in heart, esophagus, stomach, small intestine and ovary. Localizes to the crypt region of large and small intestine. At 14.5 dpc, expressed in the brain cortex, including the cortical plate, intermediate zone, and ventricular and subventricular zones. Autophosphorylated on serine and threonine residues. Phosphorylation at Thr-157 by CDK7/Cak1p increases kinase activity. Knockout mice manifest hydrocephalus, polydactyly, and delayed skeletal development. At cellular levels, ICK knockout results in abnormally elongated cilia and compromised SHH signaling. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.