Fst - follistatin

The protein encoded by this gene binds to and negatively regulates activin, as well as other members of the transforming growth factor beta family, and acts to prevent uncontrolled cellular proliferation. This protein also contains a heparin-binding sequence. It is expressed in many of the tissues in which activin is synthesized and is thought to clear activin from the circulation by attachment to the cell surface. Alternative splicing results in multiple transcript variants that encode multiple protein isoforms, including FST315 and FST288, that differ at their C-terminus. Another isoform, FST303 is thought to be produced by proteolytic cleavage of FST315. These isoforms differ in their localization and in their ability to bind heparin. While FST315 is a circulating protein, FST288 is tissue-bound, and FST303 is gonad-specific. While deletion of all isoforms results in embryonic lethality, expression of just FST288 is sufficient for embryonic development, but the resultant mice have fertility defects. [provided by RefSeq, Aug 2014]