FNDC4 and Obesity: Comparing the body weight of AAV-injected Sim1-cre mice versus AAV-injected wild-type littermates, we found that overexpression of Snca (Fig. 5g) and Igsf8 (Fig. 5h) caused an exacerbation of HFD-induced obesity, whereas overexpression of Spata2, Pole4, Fndc4, Smim12, or Arrb1 had no impact on body weight (Supplementary Fig. 8g–k).