A gain-of-function variant in RICTOR predisposes to human obesity

mTORC1/2 play central roles as signaling hubs of cell growth and metabolism and are therapeutic targets for several diseases. However, the human genetic evidence linking mutations of mTORC1/2 to obesity remains elusive. Using whole-exome sequencing of 1944 cases with severe obesity and 2161 healthy lean controls, we identify a rare RICTOR p.I116V variant enriched in 9 unrelated cases. In Rictor null mouse embryonic fibroblasts, overexpression of the RICTOR p.I116V mutant increases phosphorylation of AKT, a canonical mTORC2 substrate, compared with wild-type RICTOR, indicating a gain-of-function change. Consistent with the human obesity phenotype, the knock-in mice carrying homogenous Rictor p.I116V variants gain more body weight under a high-fat diet. Additionally, the stromal vascular fraction cells derived from inguinal white adipose tissue of knock-in mice display an enhanced capacity for adipocyte differentiation via AKT activity. These findings demonstrate that the rare gain-of-function RICTOR p.I116V mutation activates AKT signaling, promotes adipogenesis, and contributes to obesity in humans.