Horner Vanessa L, Wolfner Mariana F
Department of Molecular Biology and Genetics, 423 Biotechnology Building, Cornell University, Ithaca, NY 14853-2703, USA.
Dev Biol. 2008 Apr 1;316(1):100-9. doi: 10.1016/j.ydbio.2008.01.014. Epub 2008 Jan 26.
Embryogenesis in vertebrates and marine invertebrates begins when a mature oocyte is fertilized, resulting in a rise in intracellular calcium (Ca(2+)) that activates development. Insect eggs activate without fertilization via an unknown signal imparted to the egg during ovulation or egg laying. One hypothesis for the activating signal is that deformation of eggs as they pass through a tight orifice provides a mechanical stimulus to trigger activation. Ovulation could produce two forms of mechanical stimulus: external pressure resulting from the passage of oocytes from the ovary into the narrow oviducts, and osmotic pressure caused by hydration-induced swelling of the oocyte within the oviducts. Ovulation could also trigger activation by placing the oocyte in a new environment that contains an activating substance, such as a particular ion. Here, we provide the first evidence that Drosophila oocytes require Ca(2+) for activation, and that activation can be triggered in vitro by mechanical stimuli, specifically osmotic and hydrostatic pressure. Our results suggest that activation in Drosophila is triggered by a mechanosensitive process that allows external Ca(2+) to enter the oocyte and drive the events of activation. This will allow exploitation of Drosophila genetics to dissect molecular pathways involving Ca(2+) and the activation of development.
脊椎动物和海洋无脊椎动物的胚胎发生始于成熟卵母细胞受精，导致细胞内钙（Ca(2+)）水平升高，从而激活发育过程。昆虫卵在没有受精的情况下通过排卵或产卵过程中传递给卵的未知信号而被激活。关于激活信号的一种假设是，卵在通过狭窄孔口时的变形提供了触发激活的机械刺激。排卵可产生两种形式的机械刺激：卵母细胞从卵巢进入狭窄输卵管时产生的外部压力，以及输卵管内卵母细胞因水合作用导致肿胀而产生的渗透压。排卵还可能通过将卵母细胞置于含有激活物质（如特定离子）的新环境中来触发激活。在这里，我们提供了首个证据，表明果蝇卵母细胞的激活需要Ca(2+)，并且激活可以在体外由机械刺激，特别是渗透压和流体静压触发。我们的结果表明，果蝇中的激活是由一种机械敏感过程触发的，该过程允许外部Ca(2+)进入卵母细胞并驱动激活事件。这将有助于利用果蝇遗传学来剖析涉及Ca(2+)和发育激活的分子途径。
