CDK4 and neurodegenerative disease: As example, cell cycle proteins play a key role in neurons committed to cell death in several neurodegenerative diseases (Herrup and Yang, 2007) including inherited retinal dystrophies as well as acute retinal injury by light (Al-Ubaidi et al., 1992; Vincent et al., 1996; Yang et al., 2001; Nguyen et al., 2003; Höglinger et al., 2007; Zencak et al., 2013), where post-mitotic neurons start to express nuclear cyclin-dependent kinase 4 (CDK4), usually implicated in the re-entry into the cell cycle.