CDK8 and major depressive disorder: However, data from our aforementioned transcriptome analysis show that, at TW4, patients who developed depression had a higher expression of a distinct set of genes, including cyclin dependent kinase 5 (CDK5) and CDK8, as well as insulin-like growth factor-binding protein 5 (IGFBP5) and IGFBP7 (Hepgul et al., 2016), which are known to regulate both cell proliferation and differentiation (Alexander et al., 2004, Tanno et al., 2005).