MFN2 and obesity due to melanocortin 4 receptor deficiency: Schneeberger et al. (2013) showed that specific ablation of Mfn2 in POMC neurones causes a decrease in mitochondrial respiratory capacity and an increase in oxidative stress as well as loss of mitochondria-ER contacts, ER stress-induced leptin resistance, hyperphagia, reduced energy expenditure and obesity.