SOST and osteoporosis: Mutations in Wnt pathway genes such as WNT1 (ligand), LRP5 (co-receptor) and SOST (antagonist) have been associated with altered bone mass36 and SOST/Sclerostin blocking antibodies are in clinical trials for osteoporosis.37 Inherited inactivating mutations in Adenomatous Polyposis Coli (APC), a negative regulator of Wnt/β-catenin, cause Familial Adenomatous Polyposis (FAP).