FOXN1 and obesity due to melanocortin 4 receptor deficiency: A series of in vivo experiments using transgenic Foxn1::Egfp mice (Foxn1+/−) and B6 mice (Foxn1+/+) demonstrated that young and old Foxn1+/− mice fed HFD gained significantly less body weight than their male B6 counterparts, indicating the resistance of heterozygous Foxn1+/− mice to diet-induced obesity [13].