FTO and obesity due to melanocortin 4 receptor deficiency: Protein-protein interaction network identified a number of key “hub” genes including FTO, TMEM18, MC4R, CREB1, PPARG and TCF7L2. FTO was the first obesity susceptibility gene identified by GWASs and continued to be the locus with the largest effect on obesity risk and BMI, most widely replicated with variety of obesity traits across diverse ancestries and throughout the life course [21].