The macrophage stimulating 1 (MST1) gene is critical in the regulation of the Hippo signaling pathway, encoding the receptor kinase RON ligand macrophage-stimulating protein (MSP, also known as MST1), and is associated with the pathogenesis of primary sclerosing cholangitis (PSC) [74]. The gene discussed is MST1; the disease is sclerosing cholangitis.