ARC and obesity due to melanocortin 4 receptor deficiency: In order to furthermore clarify the role of the Arc in obesity development, we injected recombinant adeno-associated viruses encoding either Ugcg and lacZ (rAAV-Ugcg/LacZ) or only lacZ (rAAV-Empty/LacZ) bilaterally into the Arc of Ugcgf/f//CamKCreERT2 mice after ganglioside depletion before 4 wk p.i. Injection of rAAV-Ugcg/LacZ significantly ameliorated obesity, underlining the importance of Ugcg expression in the Arc for body weight maintenance (Figure 4B).