Investigating the mechanisms of Drosophila Egg Activation

我的博士学位专注于了解在卵子激活的普遍过程中发生的过程，在这个过程中，钙进入触发成熟卵母细胞中的多个下游事件，如减数分裂的恢复，翻译景观的变化，以及肌动蛋白细胞骨架的广泛变化。这个过程通常由受精触发，然而在果蝇中，这个过程是在成熟的卵母细胞经历排卵时触发的，可能是由于卵母细胞在输卵管中吸收液体时膨压增加。据认为，卵母细胞的肿胀打开了机械门控的TrpM通道，使钙能够进入。因此，我的项目主要集中在钙进入的过程是如何调节的，首先通过识别参与这一过程的钙通道，其次通过了解肌动蛋白细胞骨架的参与。这提出了一个有趣的问题，因为数据表明肌动蛋白皮质对钙离子进入有很大的影响，因此，这背后的机制是什么？我的项目将展示肌动蛋白网络作为钙流的关键调节器的数据，作为钙进入卵母细胞的屏障。我表明，肌动蛋白是耗尽在皮层的鸡蛋是为钙进入，并操纵在皮层的肌动蛋白水平影响钙进入和钙波的传播速度。此外，肌动蛋白细胞骨架的药理学操作积极阻止钙波传播。因此，问题仍然是肌动蛋白如何机械地控制钙的进入？我将进一步研究是否是由于机械门控通道的物理连接，肌动蛋白能够抵抗打开门控钙通道的物理力，或者钙进入是否作用于肌动蛋白皮质，从而破坏钙进入的屏障。

My PhD focuses on understanding the processes that occur during the universal process of egg activation, an event in which calcium entry triggers multiple downstream events in a mature oocyte, such as the resumption of meiosis, changes in the translational landscape, and broad changes in the actin cytoskeleton. This process is usually triggered by fertilization, however in Drosophila, the process is triggered as the mature oocyte undergoes ovulation, likely due to increased turgor pressure as the oocyte takes up fluid in the oviduct. It is thought that the swelling of the oocyte opens mechanically gated TrpM channels enabling the calcium to enter. Thus my project focuses largely on how the process of calcium entry is regulated, firstly through the identification of calcium channels involved in this process, and secondly through the understanding what the involvement of the actin cytoskeleton could be. This poses an interesting question, as data suggests that the actin cortex poses great influence over calcium entry, and as such, what is the mechanism behind this? My project will show data that presents the actin network as a key regulator of calcium flux, acting as a barrier for calcium entry in the oocyte. I show that actin is depleted at the cortex where the egg is primed for calcium entry, and that manipulating the level of actin at the cortex affects calcium entry and calcium wave speed propagation. Additionally, pharmacological manipulation of the actin cytoskeleton actively prevents calcium wave propagation. Questions thus remain as to how actin mechanistically controls calcium entry? I will investigate further whether it is due to the physical connection of mechanically gated channels that actin is able to transduce a physical force that opens gated calcium channels, or whether the calcium entry acts to dissociate the actin cortex and thus disrupt the barrier to calcium entry.