Nuclear size scaling during Xenopus early development contributes to midblastula transition timing.
Nuclear size scaling during Xenopus early development contributes to midblastula transition timing.
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DOI：
10.1016/j.cub.2014.10.051
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发表时间：
2015-01-05
期刊：
影响因子：
9.2
通讯作者：
Levy, Daniel L.
中科院分区：
文献类型：
--
作者：
Jevtic, Predrag;Levy, Daniel L.
非洲爪哇早期胚胎发生是一个研究发育计时机制的强大系统。在经历了一系列伴随着细胞大小缩小的快速细胞分裂后，第一个主要的发育转变是中期胚泡转变(MBT)，此时合子转录开始，细胞周期延长。虽然保持恒定的核质体积比是一种保守的细胞属性，但人们很早就认识到，在非洲爪哇发育的早期，核质体积比发生了巨大的变化。我们研究了核大小和N/C体积比在早期发育期间的变化如何有助于MBT时机的调节。虽然之前的研究表明N/C体积比在MBT计时中起作用，但没有人直接测试改变核大小的影响。在这项研究中，我们首先量化了莱氏X.laevis胚胎中的卵裂球和核的大小，表明N/C体积比在MBT之前增加。然后，我们通过显微注射不同的核比例因子来控制胚胎的核体积，包括进口蛋白、板层和网状结构。利用这种方法，我们发现增加MBT前胚胎的N/C体积比会导致合子基因转录的过早激活和较长细胞周期的提前开始。相反，降低N/C体积比会延迟合子转录，并导致额外的快速细胞分裂。虽然DNA与细胞质的比例与MBT的时序有关，但我们的数据表明，核大小也有助于MBT时序的调节，证明了核大小在发育过程中的功能意义。
Early Xenopus laevis embryogenesis is a robust system for investigating mechanisms of developmental timing. After a series of rapid cell divisions with concomitant reductions in cell size, the first major developmental transition is the midblastula transition (MBT), when zygotic transcription begins and cell cycles elongate. While the maintenance of a constant nuclear-to-cytoplasmic (N/C) volume ratio is a conserved cellular property, it has long been recognized that the N/C volume ratio changes dramatically during early Xenopus development. We investigated how changes in nuclear size and the N/C volume ratio during early development contribute to the regulation of MBT timing. While previous studies suggested a role for the N/C volume ratio in MBT timing, none directly tested the effects of altering nuclear size. In this study, we first quantify blastomere and nuclear sizes in X. laevis embryos, demonstrating that the N/C volume ratio increases prior to the MBT. We then manipulate nuclear volume in embryos by microinjecting different nuclear scaling factors, including import proteins, lamins, and reticulons. Using this approach, we show that increasing the N/C volume ratio in pre-MBT embryos leads to premature activation of zygotic gene transcription and early onset of longer cell cycles. Conversely, decreasing the N/C volume ratio delays zygotic transcription and leads to additional rapid cell divisions. While the DNA-to-cytoplasmic ratio has been implicated in MBT timing, our data show that nuclear size also contributes to the regulation of MBT timing, demonstrating the functional significance of nuclear size during development.
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