Follistatin 344 (95%)

Follistatin 344 (FS‑344) is a recombinant isoform of the follistatin protein family, derived via alternative splicing of the FST gene. This 344–amino-acid glycoprotein is present in various tissues and circulates systemically. It functions as a high-affinity binding antagonist to transforming growth factor-beta (TGF‑β) family proteins, especially myostatin and activin A. FS‑344 shows reduced affinity for activin compared to other isoforms, while retaining potent myostatin neutralizing capability.

Chemical Structure of Follistatin 344 (95%)

FS‑344 is a single-chain polypeptide composed of approximately 344 amino acids. It contains three cysteine-rich follistatin domains (FSD1–FSD3), each about 70 residues long, and an acidic C-terminal tail. The protein is glycosylated at key sites and forms a ~38 kDa monomer stabilized by multiple disulfide bonds.

What Are the Effects of Follistatin 344 (95%)?

• Myostatin Antagonism & Muscle Mass Increase: In rodent and primate studies, FS‑344 significantly increases lean muscle mass and strength by binding and neutralizing myostatin, a key inhibitor of muscle growth.
• Activin Modulation & Endocrine Interactions: FS‑344 binds activin A with lower affinity, resulting in reduced modulation of the pituitary activin–inhibin axis and follicle-stimulating hormone (FSH) secretion.
• Therapeutic Potential in Gene Therapy: Adeno-associated virus (AAV)–mediated delivery of FS‑344 improves muscle function and mobility in Becker muscular dystrophy and inclusion-body myositis models, demonstrating translational utility.
• TGF‑β Superfamily Regulation: Beyond myostatin and activin, FS‑344 influences broader TGF‑β pathways involved in tissue regeneration, fibrosis control, and muscle homeostasis.