Recombinant human/mouse/rat/bovine/porcine Activin A protein (Qk001)

Activin A is a TGFβ family growth factor regulating embryonic development, cell proliferation, differentiation, and immune responses. Activin A is frequently used to maintain pluripotency in induced pluripotent and embryonic stem cell cultures. It is also used in many stem cell differentiation protocols, including endoderm lineage differentiation and further maturation into hepatocyte and pancreatic cells.  

Recombinant human/mouse/rat/bovine/porcine activin A protein is a high-purity mature bioactive dimer of 26 kDa. It is animal-free, carrier protein-free, and tag-free to ensure its purity with exceptional lot-to-lot consistency. This protein has been rigorously benchmarked against other commercial sources and extensively validated for highly reproducible stem cell culture. Qkine founder Marko Hyvönen developed the protocol for making high-purity activin A, and this protein is used at the Cambridge Stem Cell Institute. 

High purity mature bioactive dimer. Animal-free (AOF) and carrier-protein free (CF).  Rigorously benchmarked against other commercial sources.

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1000µg will be despatched as 2 x 500µg

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  • Bioactive mature domain of recombinant human activin A protein, residues 311-426, (Uniprot: P08476)

  • >98%, by SDS-PAGE quantitative densitometry

  • 26 kDa (dimer)

  • Expressed in E. coli

  • Animal-free (AOF) and carrier protein-free.

  • Manufactured in our Cambridge, UK laboratories

  • Lyophilized from acetonitrile, TFA

  • Resuspend in 10mM HCl at >100 µg/ml, prepare single use aliquots, add carrier protein if desired and store frozen at -20°C or -80°C

Featured applications

  • Induced pluripotent and embryonic stem cell differentiation and maintenance

  • Regulated by the high-affinity inhibitor, follistatin1

ActA, Activin beta-A chain, Erythroid differentiation protein (EDP), Follicle-Stimulating Hormone (FSH) releasing protein (FRP), INHBA, Inhibin beta A, Inhibin beta 1

human, mouse, rat, bovine, porcine

Pioneering proteins badge

Follistatin resistant activin A (Qk035): a specialized form of that is resistant to follistatin feedback, developed in the lab of Marko Hyvönen (University of Cambridge)

Activin a PLUS (Qk005): optimised biologically active truncation of the mature domain of human Activin A protein, developed by Qkine.


Human Activin Qk001 protein bioactivity lot #011

Activin A activity is determined using the activin-responsive firefly luciferase reporter assay in stably transfected HEK293T cells. Cells are treated in triplicate with a serial dilution of Activin A. Firefly luciferase activity is measured and normalized. EC50 = 11.9 pM (309.4 pg/mL). Data from Qk001 lot #104276.


Human Activin A Qk001 protein purity SDS-PAGE lot #011

ActA migrates as a single band at 24 kDa in non-reducing (NR) and 13 kDa as a single monomeric species upon reduction (R).  No contaminating protein bands are visible.

Purified recombinant protein (7 µg) was resolved using 15% w/v SDS-PAGE in reduced (+β-mercaptothanol, R) and non-reduced conditions (NR) and stained with Coomassie Brilliant Blue R250.  Data from Qk001 lot #011.

Further quality assays

  • Mass spectrometry: single species with expected mass

  • Analytical reversed-phase: single sharp peak

  • Endotoxin: <0.005 EU/μg protein (below level of detection)

  • Recovery from stock vial:  >95%

We are a company founded and run by scientists to provide a service and support innovation in stem cell biology and regenerative medicine.  All our products are exceptionally high purity, with complete characterisation and bioactivity analysis on every lot.

Protein background

Activin A is a member of the belongs to the transforming growth factor beta (TGF-β) superfamily TGF-β family of growth factors [1]–[4].  It was first identified for its ability to stimulate the release of follicle-stimulating hormone (FSH) from the pituitary gland. It was later recognized as a multifunctional protein with diverse cellular effects [5], [6]. It plays crucial physiological roles in regulating embryonic development, cell proliferation, and differentiation [6], [7]. It promotes the patterning and differentiation of various organs, including the development of the mesoderm, neural, and reproductive systems. It is also involved in maintaining homeostasis, regulating immune responses, and wound healing [8]. Impaired activin A signaling has been associated with various pathological conditions, including cancer, inflammation, and fibrosis [9], [10]. As activin A can contribute to disease progression and severity, it is a growing area of research for promising therapeutic targets. 

Activins are disulfide-linked homo- and heterodimers of four inhibin β chains [6]. The best-characterized are activin A and activin B, homodimers of inhibin βA and inhibin βB, respectively. Like all other members of the TGF-β family, activins are synthesized as significant 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 essential roles in the biosynthesis, stabilization, transportation and signaling of the growth factors in the body [11]. Activin A binds to activin type I (ALK4 or ALK7) and type II (ActRIIA or ActRIIB) receptors [6], [12]. The type II receptor phosphorylates the type I receptor upon ligand binding, initiating downstream signaling cascades, mainly through the SMAD family of proteins. Activated SMAD complexes translocate into the nucleus, regulating the transcription of target genes involved in various cellular processes. In vivo, the high-affinity inhibitor follistatin and inhibins tightly regulate activin A activity in a feedback loop [13], [14].  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). 

Activin A is frequently used for the maintenance of pluripotency of human induced pluripotent stem cells and human embryonic stem cell lines along with fibroblast growth factor 2 (FGF-2) [2], [4]. Activin A is also used in various stem cell differentiation protocols. It directs the differentiation into definitive endoderm, precursor to different cell types such as pancreatic and liver cells [15]–[18]. Activin A also promotes neural precursor cells and drives astrocytic differentiation with Ciliary neurotrophic factor (CNTF) and Glial cell line-derived neurotrophic factor (GDNF) [19]. Moreover, Activin A is also involved in mesodermal differentiation to derive muscle, bone, and blood cells. Finally, activin A is often used for the development and maintenance of organoids [18], [20], [21]. Qkine recombinant activin A protein has been extensively validated and benchmarked with other suppliers’ proteins in stem cell culture and assays.  You can view the results of this analysis and a commentary by Qkine’s founder, Marko Hyvönen. 

[1] E. Piek, C. H. Heldin, and P. Ten Dijke, ‘Specificity, diversity, and regulation in TGF-beta superfamily signaling’, FASEB J. Off. Publ. Fed. Am. Soc. Exp. Biol., vol. 13, no. 15, pp. 2105–2124, Dec. 1999. 

[2] S. Pauklin and L. Vallier, ‘Activin/Nodal signalling in stem cells’, Development, vol. 142, no. 4, pp. 607–619, Feb. 2015, doi: 10.1242/dev.091769. 

[3] J. J. Lee and H. F. Rosenberg, Eds., ‘Chapter 12 – Eosinophil-Mediated Tissue Remodeling and Fibrosis’, in Eosinophils in Health and Disease, Boston: Academic Press, 2013, pp. 391–429. doi: 10.1016/B978-0-12-394385-9.00012-2. 

[4] L. Vallier, M. Alexander, and R. A. Pedersen, ‘Activin/Nodal and FGF pathways cooperate to maintain pluripotency of human embryonic stem cells’, J. Cell Sci., vol. 118, no. 19, pp. 4495–4509, Oct. 2005, doi: 10.1242/jcs.02553. 

[5] R. S. Carroll, P. M. Kowash, J. A. Lofgren, R. H. Schwall, and W. W. Chin, ‘In vivo regulation of FSH synthesis by inhibin and activin’, Endocrinology, vol. 129, no. 6, pp. 3299–3304, Dec. 1991, doi: 10.1210/endo-129-6-3299. 

[6] Y. Xia and A. L. Schneyer, ‘The Biology Of Activin: Recent Advances In Structure, Regulation And Function’, J. Endocrinol., vol. 202, no. 1, pp. 1–12, Jul. 2009, doi: 10.1677/JOE-08-0549. 

[7] S. Sulzbacher, I. S. Schroeder, T. T. Truong, and A. M. Wobus, ‘Activin A-Induced Differentiation of Embryonic Stem Cells into Endoderm and Pancreatic Progenitors—The Influence of Differentiation Factors and Culture Conditions’, Stem Cell Rev. Rep., vol. 5, no. 2, pp. 159–173, Jun. 2009, doi: 10.1007/s12015-009-9061-5. 

[8] G. Hübner, Q. Hu, H. Smola, and S. Werner, ‘Strong Induction of Activin Expression after Injury Suggests an Important Role of Activin in Wound Repair’, Dev. Biol., vol. 173, no. 2, pp. 490–498, Feb. 1996, doi: 10.1006/dbio.1996.0042. 

[9] H. A. Loomans and C. D. Andl, ‘Intertwining of Activin A and TGFβ Signaling: Dual Roles in Cancer Progression and Cancer Cell Invasion’, Cancers, vol. 7, no. 1, Art. no. 1, Mar. 2015, doi: 10.3390/cancers7010070. 

[10] K. L. Jones, D. M. de Kretser, Shane. Patella, and D. J. Phillips, ‘Activin A and follistatin in systemic inflammation’, Mol. Cell. Endocrinol., vol. 225, no. 1, pp. 119–125, Oct. 2004, doi: 10.1016/j.mce.2004.07.010. 

[11] X. Wang, G. Fischer, and M. Hyvönen, ‘Structure and activation of pro-activin A’, Nat. Commun., vol. 7, no. 1, Art. no. 1, Jul. 2016, doi: 10.1038/ncomms12052. 

[12] L. S. Mathews, ‘Activin Receptors and Cellular Signaling by the Receptor Serine Kinase Family’, Endocr. Rev., vol. 15, no. 3, pp. 310–325, Jun. 1994, doi: 10.1210/edrv-15-3-310. 

[13] A. E. Harrington, S. A. Morris-Triggs, B. T. Ruotolo, C. V. Robinson, S. Ohnuma, and M. Hyvönen, ‘Structural basis for the inhibition of activin signalling by follistatin’, EMBO J., vol. 25, no. 5, pp. 1035–1045, Mar. 2006, doi: 10.1038/sj.emboj.7601000. 

[14] C. Welt, Y. Sidis, H. Keutmann, and A. Schneyer, ‘Activins, inhibins, and follistatins: from endocrinology to signaling. A paradigm for the new millennium’, Exp. Biol. Med. Maywood NJ, vol. 227, no. 9, pp. 724–752, Oct. 2002, doi: 10.1177/153537020222700905. 

[15] K. A. D’Amour, A. D. Agulnick, S. Eliazer, O. G. Kelly, E. Kroon, and E. E. Baetge, ‘Efficient differentiation of human embryonic stem cells to definitive endoderm’, Nat. Biotechnol., vol. 23, no. 12, Art. no. 12, Dec. 2005, doi: 10.1038/nbt1163. 

[16] L. Andreasson, H. Evenbratt, R. Mobini, and S. Simonsson, ‘Differentiation of induced pluripotent stem cells into definitive endoderm on Activin A-functionalized gradient surfaces’, J. Biotechnol., vol. 325, pp. 173–178, Jan. 2021, doi: 10.1016/j.jbiotec.2020.10.030. 

[17] S. Ghorbani-Dalini et al., ‘Optimization of activin-A: a breakthrough in differentiation of human induced pluripotent stem cell into definitive endoderm’, 3 Biotech, vol. 10, no. 5, p. 215, Apr. 2020, doi: 10.1007/s13205-020-02215-3. 

[18] S. Qiu et al., ‘An Efficient Method for the Differentiation of Human iPSC-Derived Endoderm toward Enterocytes and Hepatocytes’, Cells, vol. 10, no. 4, Art. no. 4, Apr. 2021, doi: 10.3390/cells10040812. 

[19] C. Arber et al., ‘Activin A directs striatal projection neuron differentiation of human pluripotent stem cells’, Development, vol. 142, no. 7, pp. 1375–1386, Apr. 2015, doi: 10.1242/dev.117093. 

[20] C. C. Miranda, T. G. Fernandes, M. M. Diogo, and J. M. S. Cabral, ‘Towards Multi-Organoid Systems for Drug Screening Applications’, Bioengineering, vol. 5, no. 3, Art. no. 3, Sep. 2018, doi: 10.3390/bioengineering5030049. 

[21] L. Shariati, Y. Esmaeili, S. Haghjooy Javanmard, E. Bidram, and A. Amini, ‘Organoid Technology: Current Standing and Future Perspectives’, Stem Cells, vol. 39, no. 12, pp. 1625–1649, Dec. 2021, doi: 10.1002/stem.3379. 


Additional resources

Qkine Activin A technote

Technote: Activin A vial recovery


Activin A is a multifunctional protein. It is involved in regulating embryonic development, cell proliferation, and differentiation. It promotes the patterning and differentiation of various organs, including the development of the mesoderm, neural, and reproductive systems. It is also involved in maintaining homeostasis, regulating immune responses, and wound healing. Finally, it stimulates the release of follicle-stimulating hormone from the pituitary gland. 

Activin A is a critical factor in stem cell culture, commonly used to maintain the pluripotency of human induced pluripotent stem cells (iPSCs) and human embryonic stem cells (ESCs). It is integral to various stem cell differentiation protocols, guiding the differentiation of the definitive endoderm, neural and mesodermal lineages. Activin A is also commonly utilized in the development and maintenance of organoids. 

Activin A and inhibin A are closely related proteins in the TGF-β superfamily. They share structural similarities but have distinct functions and roles in regulating various physiological processes. Activin A has broader functions beyond reproduction, which include handling embryonic development, stem cell maintenance, and the immune system. Inhibin A, conversely, is more specifically associated with the feedback control of follicle-stimulating hormones in the context of reproductive physiology. 

Activin A binds to activin type I (ALK4 or ALK7) and type II (ActRIIA or ActRIIB) receptors to activate downstream SMAD signalling. 

Yes, activin is involved in a feedback loop that regulates the secretion of follicle-stimulating hormone (FSH) and luteinising hormone (LH). 

The activin gene family includes several genes that encode different activin subunits, forming various activin isoforms such as Inhibin Beta  Subunits (INHBA / INHBB / INHBC / INHBD). 

Follistatin and inhibins tightly regulate activin A activity in a feedback loop. 


Nat Cell Biol. 2024
Distinct pathways drive anterior hypoblast specification in the implanting human embryo.
Authors: Weatherbee, B.A.T., Weberling, A., Gantner, C.W. et al.
Labs: Magdalena Zernicka-Goetz, University of Cambridge

Nat Commun. 2024
Self-renewing human naïve pluripotent stem cells dedifferentiate in 3D culture and form blastoids spontaneously
Authors: Guo, M., Wu, J., Chen, C. et al.
Labs: José Silva, Guangzhou Laboratory

Our products are for research use only and not for diagnostic or therapeutic use.  Products are not for resale.

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  1. Stem cell researcher, University of Oxford, UK

    Qkine Activin A works nicely for human pluripotent stem cell differentiation to endoderm

    Stem cell researcher, University of Oxford, UK

    We are using Qkine Activin A and it works nicely for human pluripotent stem cell differentiation to endoderm. University of Oxford, UK.

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