REG4 and obesity due to melanocortin 4 receptor deficiency: Since Reg4/REG4 is highly homologous between mice and humans (66% amino acid sequence homology), we also generated transgenic mice expressing REG4 in their intestinal epithelial cells (huREG4IECtg) (Fig. S1c-e) to further investigate the role of gut Reg4 in HFD-mediated obesity.