ACVR1C and obesity due to melanocortin 4 receptor deficiency: In conclusion, our analysis of the physiological and biochemical effects of three missense variants in mouse Acvr1c, which in humans correlate with reduced fat deposition, revealed metabolic alterations of graded strength, including resistance to diet-induced obesity, that correlated with the extent to which each variant affected ALK7 signaling in adipocytes.