Dyson S, Gurdon J B
Wellcome/CRC Institute, Cambridge, United Kingdom.
Cell. 1998 May 15;93(4):557-68. doi: 10.1016/s0092-8674(00)81185-x.
Xenopus blastula cells activate different mesodermal genes as a concentration-dependent response to activin, which behaves like a morphogen. To understand how cells recognize morphogen concentration, we have bound naturally labeled activin to cells and related this to choice of gene activation. We find that the increasing occupancy of a single receptor type can cause cells to switch gene expression. Cells sense ligand concentration by the absolute number of occupied receptors per cell (100 and 300 molecules of bound activin induce Xbra and Xgsc, respectively, i.e., 2% and 6% of the total receptors) and not by a ratio of occupied to unoccupied receptors. The long duration of occupancy explains a previously described ratchet effect. Our results suggest a new concept of morphogen gradient formation and interpretation that is particularly well suited to the needs of early development.
非洲爪蟾囊胚细胞对激活素（一种形态发生素）产生浓度依赖性反应，从而激活不同的中胚层基因。为了了解细胞如何识别形态发生素浓度，我们将天然标记的激活素与细胞结合，并将其与基因激活的选择联系起来。我们发现，单一受体类型占有率的增加可导致细胞切换基因表达。细胞通过每个细胞中被占据受体的绝对数量来感知配体浓度（分别有100和300个结合激活素分子诱导Xbra和Xgsc，即占总受体的2%和6%），而不是通过被占据与未被占据受体的比例。占据的长时间解释了先前描述的棘轮效应。我们的结果提出了一种形态发生素梯度形成和解读的新概念，这特别适合早期发育的需求。
