本文介绍了激活卵子在果蝇中可视化钙离子的适应体外协议。
Egg activation is a universal process that includes a series of events to allow the fertilized egg to complete meiosis and initiate embryonic development. One aspect of egg activation, conserved across all organisms examined, is a change in the intracellular concentration of calcium (Ca2+) often termed a ‘Ca2+ wave’. While the speed and number of oscillations of the Ca2+ wave varies between species, the change in intracellular Ca2+ is key in bringing about essential events for embryonic development. These changes include resumption of the cell cycle, mRNA regulation, cortical granule exocytosis, and rearrangement of the cytoskeleton.
In the mature Drosophila egg, activation occurs in the female oviduct prior to fertilization, initiating a series of Ca2+-dependent events. Here we present a protocol for imaging the Ca2+ wave in Drosophila. This approach provides a manipulable model system to interrogate the mechanism of the Ca2+ wave and the downstream changes associated with it.
在蛋(卵母细胞)的激活细胞内钙的变化2+浓度是所有研究的有机体1,2的保守成分。该事件启动了广泛的Ca 2+依赖性的过程,包括细胞周期的恢复和存储mRNA的翻译。由于这一要求的钙离子 ,可视化细胞内钙离子浓度瞬时变化是关键的兴趣。
历史上,被选定为基于它们的卵的大小和可用性上激活卵子的研究模式生物。各种可视化的方法已被用于跟踪和细胞内Ca量化改变在这些系统中2+浓度,其中包括:在青鳉鱼3的光蛋白水母发光蛋白; 的 Ca 2+敏感的荧光染料如的Fura-2在海胆和仓鼠4,5;和钙绿-1-葡聚糖在爪 6。
的产生和基因编码的钙指标(GECIS)改进已经改变可视化钙动力学体内 7的能力。这些遗传构建体在特定组织中表达,并限制对侵入组织标本8的必要性。
GCaMPs是绿色荧光蛋白(GFP)基类已经非常有效GECIS的,由于其高的 Ca 2+亲和力,信噪比和能力来定制9-11。在钙离子的存在下,在GCaMP复杂经历一系列的构象变化,开始与钙离子的钙调蛋白的结合,即结果在GFP元器件9的增加的荧光强度。
GCaMPs已在研究被广泛用在果蝇神经元的可视化细胞内钙12的变化。最近applicati在GCaMP技术成熟果蝇卵可视化钙离子已经揭示了蛋激活13,14一个短暂的钙波。在钙离子波可以在低倍镜下采用体外活化试验13,14 体内排卵13期间或在更高的放大倍率可视化。在体外测定中,单独的成熟卵母细胞从卵巢中分离,并用低渗溶液激活,称为活化缓冲液,这已被证明是概括在体内活化15-17的事件。
这种体外试验使不同的实验条件,包括药理中断,物理处理和基因突变下的钙波易高分辨率可视化。本文展示了成熟的卵子果蝇对体外激活和日准备用于可视化使用GCaMP的钙波ê随后的显微镜。这种方法可以用于测试的 Ca 2+波的起始和控制,并探测下游结果。
The first critical step in this protocol is isolating the mature eggs without damage. This can be achieved by gentile maneuvering of the eggs with the dissecting probe. Practice will enable this manipulation to be executed without damage to the eggs. A second crucial step is avoiding the loss of the sample when activation buffer is applied to the mature egg in oil. Application of the activation buffer should be done slowly and without contact with the coverslip. This step can be challenging if the microscope set-up does not allow for an easy access to the sample. Moving axillary parts of the microscope, such as a temperature incubator, is advisable.
Modifications to this protocol can be made in order to visualize other fluorescently tagged factors, instead of Ca2+ at egg activation. More generally, different stages of Drosophila development or the results of adding a different buffer could be analyzed using this protocol.
Troubleshooting may be required if the settings on the microscope are not optimal for visualizing the signal from the sample. This can be achieved by increasing or decreasing the laser power, altering capture range and adjusting the Z-stack parameters. Another issue might be eggs consistently moving out of the field of view upon the addition of activation buffer. If this happens regularly, allow the mature eggs to settle on the coverslips for a longer period of time, 15 to 20 minutes. Beware that using a higher viscosity oil will alter the displacement of the oil by activation buffer.
This technique presented here is limited by the working distance of the objective, dehydration of the mature eggs and the ability to dissect the mature eggs without damage. However, when compared to in vivo imaging methods where the mature oocyte passes through the adult female and is deposited 13, our method enables more spatial resolution, the option to physically manipulate the mature egg before activation and the ability to test the role of egg activation without fertilization.
There are many potential future applications of this technique, including testing reporter constructs for cellular components at egg activation and visualizing the Ca2+ wave in mutant backgrounds 14,24. Together with experimental and genetic tools, the ex vivo egg activation assay presented here enables the study of the trigger, propagation and downstream effects of the universally conserved Ca2+ wave.
The authors have nothing to disclose.
我们感谢劳拉班普顿,亚历克斯·戴维森,理查德·帕顿,阿查里雅田对这个手稿的准备过程中提供援助;马里亚纳Wolfner对鸡蛋激活讨论;马特·韦兰成像的支持;和胡楠在实验室普遍支持。
这项工作是由剑桥,ISSF的大学TTW [授权号097814]的支持。
Dry active yeast | Fleischman’s | #2192 | |
Dissecting microscope | Leica | MZ6 | Various will work |
Lamp | Mircotec Fibre optic | MF0-90 | Various will work |
Medical wipes | Kimberly-Clark Corporation | KLEW3020 | |
Marker pen | Stabilo | 841/46 | OHPen universal, black – available in most stationary shops. Superfine Width 0.4mm |
CO2 pad | Genesee Scientific | 59-114 (789060 Dutscher) | |
Cover slip No. 1.5, 22 x 50mm | International- No1-VWR Cat=631-0137-22-50mm | Menzel-Glaser-22-50mm-MNJ 400-070T | |
Halocarbon oil, series 95 | Halocarbon Products Corp. | Distributor in Europe: | |
Solvadis (GMBH) | |||
Oil 10 S | VWR Chemicals | 24627.188 | Can be used instead of Halocarbon oil, series 95 |
Forceps | Fine Science Tools | 11252-00 | Whilst these tool should be clean, use of an autoclave is not necessary, ethanol would be sufficient. |
Probe | Fine Science Tools | 10140-01 | |
Glass pipette | Fisherbrand, | FB50251 | Pasteur Pipettes, glass, unplugged, 150mm length |
Vial | Regina Industries | P1014 | GPPS 80mm x 25mm |