CDKL5 and Rett syndrome: Noteworthy, two other genes, also identified to cause RTT, cyclin-dependent kinase-like 5 (CDKL5) and forkhead box protein G1 (FOXG1), are thought to converge on MECP2 [33,34]: MECP2 is an enzymatic target of CDKL5, while FOXG1 interacts with the MECP2-isoform (MECP2-e2; one of two MECP2-isoforms) that prevents cell death of cerebellar neurons [35].