Follistatin 344 (FST344) is a recombinant human glycoprotein consisting of 344 amino acids, with an approximate molecular weight of 37,000 g/mol in its glycosylated form. It is the full-length isoform of Follistatin, first identified as a follicle-stimulating hormone (FSH) inhibiting factor in ovarian follicular fluid. FST344 contains three cysteine-rich Follistatin domains with EGF-like and Kazal-like motifs, an N-terminal atypical TGF-binding domain, and a highly acidic C-terminal tail. Produced via recombinant expression, Follistatin 344 functions as a high-affinity binding protein for multiple TGF-beta superfamily ligands including Activin and Myostatin (GDF-8).

Follistatin 344 is one of the most extensively investigated endogenous antagonists of the TGF-beta superfamily in preclinical research. Its capacity to bind and neutralise both Activin and Myostatin has established it as a key reference compound in studies examining the regulation of skeletal muscle mass, reproductive endocrinology, and tissue remodelling. In vitro studies in cell-based neutralisation and receptor-binding preparations have characterised FST344’s binding stoichiometry and neutralisation kinetics with Activin A and GDF-8, documenting distinct affinity profiles across the FST isoform panel, with FST288 exhibiting the highest Activin binding affinity and FST344 showing broader tissue distribution attributable to its lower heparin-binding capacity [1]. In vivo rodent studies have examined skeletal muscle phenotypes following Follistatin gene delivery in preclinical rodent models, documenting long-term increases in skeletal muscle mass and strength and characterising the mechanism within the ActRIIB signalling axis and downstream SMAD-dependent transcriptional programmes [2], making Follistatin 344 a key reference compound in multi-ligand antagonism research within the TGF-beta superfamily.

Follistatin 344 is manufactured in a cGMP compliant laboratory to a guaranteed purity of 98% or above. Every batch is independently tested using HPLC and MS-UPLC analysis before dispatch. Vials are vacuum sealed and stored in a temperature controlled, monitored cold storage system. Certificates of Analysis are available on request.

Sold strictly for in vitro research purposes only. Not for human consumption. Intended for use by qualified researchers in laboratory settings only.

Editorial Team

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed and approved 14 June 2026

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