Activin A is a member of the TGFβ family of growth factors. Activin A is used frequently in stem cell differentiation and maintenance media. It also has vital physiological roles in the regulation of embryogenesis, development of the reproductive system, wound healing and regulation of immune responses. In vivo, the high-affinity inhibitor follistatin and inhibins tightly regulate activin A activity (1). Follistatin is secreted into the media during stem cell culture. However, the impact on the efficiency of stem cell differentiation and cellular homogeneity has not been studied closely (see this discussion for more information).
Activins are disulfide-linked homo- and heterodimers of four inhibin β chains. The best-characterized are activin A and activin B, homodimers of inhibin βA and inhibin βB, respectively. Activins, like all other members of the TGF-β family, are synthesized as large precursors consisting of an N-terminal signal peptide, a pro-domain of 250–350 residues and a highly conserved mature domain. The pro-domain, which is cleaved off in the mature protein, has important roles in the biosynthesis, stabilization, transportation and signalling of the growth factors in the body2.
Recombinant activin A is used in stem cell maintenance of pluripotency in many human induced pluripotent stem cell and human embryonic stem cell lines3, and to induce stem cell differentiation into definitive endoderm4 and other cell fates.
Qkine recombinant activin A protein has been extensively validated and benchmarked with other suppliers’ proteins in stem cell culture and other assays. You can view the results of this analysis and a commentary by Qkine’s founder Marko Hyvönen.