Diffusion and scaling during early embryonic pattern formation
Diffusion and scaling during early embryonic pattern formation
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DOI：
10.1073/pnas.0509483102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Wieschaus, EF
中科院分区：
文献类型：
--
作者：
Gregor, T;Bialek, W;Wieschaus, EF
多细胞生物中空间模式的发展取决于控制基因表达的信号分子浓度的梯度。在果蝇的胚胎中，双聚体（BCD）形态学控制着沿着70％前后轴的细胞命运，但从前极局部的mRNA翻译。人们认为BCD和其他形态的梯度是通过扩散而产生的，但是这种基本假设从未在活着的胚胎中进行严格测试。此外，由于扩散会在长度和时间尺度之间建立关系，因此很难看到通过扩散建立的基因表达模式如何随着卵大小在进化过程中的变化而成比例地缩放。在这里，我们表明，惰性分子通过胚胎的运动在相关的长度和时间尺度上的扩散方程很好地描述了，并且在与胚胎的胚胎非常不同的胚胎的紧密相关的双翅目物种中，有效的扩散常数基本相同。尽管如此，在这些不同物种尺度上具有卵长度的基因表达模式。我们表明，这种缩放可以追溯到BCD梯度本身的缩放。我们的结果以及由发育时间尺度施加的约束，表明缩放机制是BCD寿命的物种特异性适应。
Development of spatial patterns in multicellular organisms depends on gradients in the concentration of signaling molecules that control gene expression. In the Drosophila embryo, Bicoid (Bcd) morphogen controls cell fate along 70% of the anteroposterior axis but is translated from mRNA localized at the anterior pole. Gradients of Bcd and other morphogens are thought to arise through diffusion, but this basic assumption has never been rigorously tested in living embryos. Furthermore, because diffusion sets a relationship between length and time scales, it is hard to see how patterns of gene expression established by diffusion would scale proportionately as egg size changes during evolution. Here, we show that the motion of inert molecules through the embryo is well described by the diffusion equation on the relevant length and time scales, and that effective diffusion constants are essentially the same in closely related dipteran species with embryos of very different size. Nonetheless, patterns of gene expression in these different species scale with egg length. We show that this scaling can be traced back to scaling of the Bcd gradient itself. Our results, together with constraints imposed by the time scales of development, suggest that the mechanism for scaling is a species-specific adaptation of the Bcd lifetime.