MEF2D and neurodegenerative disease: Take GSK3β, a protein kinase that is critical in the pathogenesis of neurodegenerative disease, as an example, removal of depolarization and exposure to PD-related neurotoxins (MPP+, 6-OHDA) over-activated GSK3β in CGNs, leading to GSK3β-dependent inhibition of MEF2D function and neuronal death (Guo et al., 2017), whereas over-expression of MEF2D mutant could be resistant to GSK3β inhibition and further protected neurons from such neurotoxicity (Wang et al., 2009).