Membrane-anchored forms may play a role in cellular adhesion. Megakaryocyte-potentiating factor (MPF) may potentiate megakaryocyte colony formation. Interacts with MUC16. Highly expressed in lung and heart. Expressed at low levels in spleen, liver, kidney and testis. Present in lung (at protein level). Expressed at 7 dpc, down-regulated at 11 dpc, re-expressed at 15 dpc and peaks at 17 dpc. Present in embryonic diaphragm (at protein level). By WNT1 but not by WNT5A in mammary epithelial cells. Proteolytically cleaved by a furin-like convertase to generate megakaryocyte-potentiating factor (MPF), and the cleaved form of mesothelin. Mice have normal growth and reproductive function, and normal platelet counts. Belongs to the mesothelin family.