We have developed a model of CDD in Drosophila based on downregulation of the single Cdkl gene by RNAi, which results in phenotypes similar to those of CDD patients, that are rescued by re-expression of fly Cdkl and human CDKL5. CDKL proteins contain a conserved kinase domain, originally involved in ciliary maintenance; therefore, invertebrate model organisms can be used to investigate CDKL functions that involve the aforementioned domain. The gene discussed is CDKL5; the disease is craniodiaphyseal dysplasia.