Follistatin

Follistatin is a secreted, cysteine-rich glycoprotein that functions as a high-affinity binding partner for several ligands of the TGF-β superfamily, most notably myostatin (GDF-8) and the activins. It circulates in isoforms arising from alternative splicing and proteolytic processing (commonly referenced as FS-288 and FS-315) that differ in cell-surface affinity. It is a folded, glycosylated protein produced recombinantly as a research reference material rather than a short synthetic peptide. As a macromolecule it is handled with care against denaturation.

The research literature characterizes follistatin through irreversible, high-affinity sequestration of its target ligands: by binding myostatin and activin it prevents their engagement of activin type-II receptors, functionally antagonizing that arm of TGF-β-superfamily signaling. In myogenic systems this myostatin neutralization is associated with relief of the SMAD2/3 signaling that normally restrains muscle-cell growth. The literature also describes modulation of activin-dependent pathways relevant to follicular development and of TGF-β-dependent fibrotic signaling. Its activity is characterized at the ligand-binding and receptor level.

Contexts in which this compound appears in the in-vitro and preclinical research literature:

• Myoblast culture: myostatin neutralization and attenuated SMAD2/3 signaling endpoints.
• Preclinical gene-transfer studies reporting muscle-hypertrophy phenotypes in animal models.
• Ligand-binding assays characterizing affinity for myostatin, activin, and related GDFs.
• Models of activin-regulated follicular development and reproductive signaling.
• Fibrosis models examining attenuation of TGF-β-dependent signaling.

Supplied as a lyophilized protein for laboratory reconstitution. Reconstitute gently with bacteriostatic water (or your protocol's specified diluent) to the working concentration required (e.g. adding 2.2 mL to the 11 mg vial yields 5 mg/mL). Direct the diluent down the vial wall and swirl to dissolve; do not shake or vortex, as agitation can denature the glycoprotein. Aliquot after reconstitution to avoid repeated freeze–thaw.

Store the sealed lyophilized vial at −20 °C protected from light. Reconstituted protein is labile — keep refrigerated at 2–8 °C, use within a short assay window, and avoid repeated freeze–thaw.

A certificate of analysis for the current lot is in preparation and will be published in the certificate library. Lot documentation is available on request for this compound.