This gene encodes a member of the casein kinase I gene family. This family is comprised of serine/threonine kinases that phosphorylate acidic proteins such as caseins. The encoded kinase plays a role in cell cycle checkpoint arrest in response to stalled replication forks by phosphorylating Claspin. A mutation in this gene may be associated with non-syndromic early-onset epilepsy (NSEOE).