Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada.
Biophys J. 2010 Aug 9;99(4):L33-5. doi: 10.1016/j.bpj.2010.05.031.
The Bicoid (Bcd) morphogen is essential for pattern formation in fruit flies. It forms an exponential concentration gradient along the embryo AP axis and turns on cascades of target genes in distinct anterior domains. The most commonly accepted model for gradient formation assumes that Bcd travels by simple diffusion and is uniformly degraded across syncytial embryos, yet several recent studies have challenged these ideas. Here, the question of Bcd mobility was investigated using fluorescence correlation spectroscopy in live Drosophila melanogaster embryos. Bcd-EGFP molecules were found to be highly mobile in the cytoplasm during cycles 12-14, with a diffusion coefficient approximately 7 microm(2)/s. This value is large enough to explain the stable establishment of the Bcd gradient simply by diffusion before cycle 8, i.e., before the onset of zygotic transcription.
Bicoid (Bcd) 形态发生素对于果蝇的模式形成至关重要。它在胚胎 AP 轴上形成指数浓度梯度，并在前部区域中开启一系列靶基因级联反应。梯度形成的最常见模型假设 Bcd 通过简单扩散，并在合胞胚胎中均匀降解，然而最近的几项研究挑战了这些观点。在这里，使用荧光相关光谱法在活体黑腹果蝇胚胎中研究了 Bcd 的迁移性。发现 Bcd-EGFP 分子在周期 12-14 期间在细胞质中具有高度的流动性，扩散系数约为 7 微米 2/秒。这个值足以解释在周期 8 之前，即在合子转录开始之前，Bcd 梯度仅通过扩散就可以稳定建立。
