MEF2A and obesity due to melanocortin 4 receptor deficiency: Restoration of Erk5 expression by the AAV9 approach alleviates mitochondrial dysfunction and subsequent maladies, revealing a potential new strategy to mitigate metabolic cardiomyopathy from obesity and diabetes (Fig. 9).Transcription factors responsible for the control of Pgc-1α gene expression include Mef2, Creb, and Klf417–19.