Instituto de Fisiología Celular-Neurociencias, Universidad Nacional Autónoma de México, México, México.
PLoS One. 2012;7(8):e43797. doi: 10.1371/journal.pone.0043797. Epub 2012 Aug 22.
Activin A is a protein that participates principally in reproductive functions. In the adult brain, Activin is neuroprotective, but its role in brain development is still elusive.
METHODOLOGY/PRINCIPAL FINDINGS: We studied if Activin A influences proliferation, differentiation or survival in rat cerebrocortical neural progenitor cells (NPC). After stimulation of NPC with Activin A, phosphorylation and nuclear translocation of Smad 2/3 were induced. In proliferating NPC, Activin produced a significant decrease in cell area and also a discrete increase in the number of neurons in the presence of the mitogen Fibroblast Growth Factor 2. The percentages of cells incorporating BrdU, or positive for the undifferentiated NPC markers Nestin and Sox2, were unchanged after incubation with Activin. In differentiating conditions, continuous treatment with Activin A significantly increased the number of neurons without affecting astroglial differentiation or causing apoptotic death. In cells cultured by extended periods, Activin treatment produced further increases in the proportion of neurons, excluding premature cell cycle exit. In clonal assays, Activin significantly increased neuronal numbers per colony, supporting an instructive role. Activin-induced neurogenesis was dependent on activation of its receptors, since incubation with the type I receptor inhibitor SB431542 or the ligand-trap Follistatin prevented neuronal differentiation. Interestingly, SB431542 or Follistatin by themselves abolished neurogenesis and increased astrogliogenesis, to a similar extent to that induced by Bone Morphogenetic Protein (BMP)4. Co-incubation of these Activin inhibitors with the BMP antagonist Dorsomorphin restored neuronal and astrocytic differentiation to control levels.
Our results show an instructive neuronal effect of Activin A in cortical NPC in vitro, pointing out to a relevant role of this cytokine in the specification of NPC towards a neuronal phenotype.
激活素 A 是一种主要参与生殖功能的蛋白质。在成年大脑中，激活素具有神经保护作用，但它在大脑发育中的作用仍不清楚。
方法/主要发现：我们研究了激活素 A 是否影响大鼠大脑皮质神经祖细胞 (NPC) 的增殖、分化或存活。在 NPC 受到激活素 A 刺激后，Smad 2/3 发生磷酸化并转位到核内。在增殖的 NPC 中，激活素 A 在存在有丝分裂原成纤维细胞生长因子 2 的情况下，显著减小细胞面积，并使神经元数量略有增加。在孵育激活素后，细胞中掺入 BrdU 的比例或未分化 NPC 标志物巢蛋白和 Sox2 的阳性细胞比例没有变化。在分化条件下，持续用激活素 A 处理显著增加神经元数量，而不影响星形胶质细胞分化或导致细胞凋亡。在延长培养的细胞中，激活素处理进一步增加神经元的比例，排除过早的细胞周期退出。在克隆分析中，激活素显著增加每个克隆的神经元数量，支持其具有指导作用。激活素诱导的神经发生依赖于其受体的激活，因为用 I 型受体抑制剂 SB431542 或配体陷阱 follistatin 孵育可阻止神经元分化。有趣的是，SB431542 或 follistatin 本身会消除神经发生并增加星形胶质细胞发生，其程度与骨形态发生蛋白 (BMP)4 诱导的程度相似。将这些激活素抑制剂与 BMP 拮抗剂 Dorsomorphin 共同孵育可使神经元和星形胶质细胞分化恢复到对照水平。
我们的结果显示，激活素 A 在体外皮质 NPC 中具有指导神经元的作用，这表明这种细胞因子在 NPC 向神经元表型分化中具有重要作用。
