Mesothelin, also known as MSLN, is a protein that in humans is encoded by the MSLN gene.Cloning studies showed that the mesothelin gene encodes a precursor protein that is processed to yield mesothelin which is attached to the cell membrane by a glycophosphatidylinositol linkage and a 31-kDa shed fragment named megakaryocyte-potentiating factor (MPF). Although it has been proposed that mesothelin may be involved in cell adhesion, its biological function is not known.A knockout mouse line that lacks mesothelin reproduces and develops normally.