Kuroda Hiroki, Fuentealba Luis, Ikeda Atsushi, Reversade Bruno, De Robertis E M
Howard Hughes Medical Institute and Department of Biological Chemistry, University of California, Los Angeles, CA 90095-1662, USA.
Genes Dev. 2005 May 1;19(9):1022-7. doi: 10.1101/gad.1306605.
Xenopus embryonic ectodermal cells dissociated for three or more hours differentiate into neural tissue instead of adopting their normal epidermal fate. This default type of neural induction occurs in the absence of Spemann's organizer signals and is thought to be caused by the dilution of endogenous BMPs into the culture medium. Unexpectedly, we observed that BMP ligands continue to signal in dissociated cells. Instead, cell dissociation induces a sustained activation of the Ras/MAPK pathway, which causes the phosphorylation of Smad1 at sites that inhibit the activity of this transcription factor. It is this activation of Ras/MAPK that is required for neuralization in dissociated ectoderm.
非洲爪蟾胚胎外胚层细胞解离三个或三个小时以上会分化为神经组织，而不是正常地分化为表皮组织。这种默认的神经诱导类型在没有施佩曼组织者信号的情况下发生，并且被认为是由内源性骨形态发生蛋白（BMP）稀释到培养基中所导致的。出乎意料的是，我们观察到BMP配体在解离的细胞中继续发出信号。相反，细胞解离会诱导Ras/丝裂原活化蛋白激酶（MAPK）途径的持续激活，这会导致Smad1在抑制该转录因子活性的位点发生磷酸化。正是这种Ras/MAPK的激活是解离外胚层神经化所必需的。
