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New insights into the roles of cytoplasmic F-actin self-organization using two model systems : Xenopus egg extracts and mouse oocytes

Abstract : Cell division is a key element of the development of an embryo throughout all his life. During cell division, the genetic material (chromosomes) is distributed between the two daughter cells. This distribution is achieved by the spindle and a misbehavior in the formation of this structure can be critical. The cytoskeleton polymers are playing a predominant role in cell division. Despite important progresses in the understanding of their role in cell division process, numerous questions still have to be answered and technical progresses to study these phenomena are still needed. In this PhD work, we studied the role of cytoplasmic F-actin self-organization in two model systems: Xenopus egg extracts and mouse oocytes. Using an interdisciplinary approach, we developed new experimental and analytical tools to study the role of cytoplasmic F-actin during cell division. By encapsulating Xenopus actin-intact egg extracts in droplets, we are able to mimic cellular environment. We use this system to study interactions between F-actin and microtubules. In a first project, we showed that F-actin self-organization can trigger signaling pathways. By engineering two properties of the microfilament self-organization and using Ran dependent microtubule nucleation, we found that F-actin dynamics promotes the robust assembly of microtubules. In a second project, we showed that the dynamics of cytoplasmic F-actin can induce constraints on the microtubule organization and dynamics in aster and spindle structures. Our results suggest that the dynamic properties of cytoplasmic F-actin meshwork are of a primary importance for the proper assembly of microtubule structures.In the mouse oocyte, we set-up a method to automatically track the movement of passive objects with tunable size. We used this system to examine the effect of cytoplasmic F-actin on long-range transport. We thus validated the existence of a non-specific mechanism for large objects centering during Prophase. We also demonstrated that this centering mechanism is still present during the rest of meiosis, coexisting with the spindle migration toward the cortex.
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Submitted on : Thursday, May 31, 2018 - 2:40:22 PM
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  • HAL Id : tel-01804191, version 1

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Alexandra Colin. New insights into the roles of cytoplasmic F-actin self-organization using two model systems : Xenopus egg extracts and mouse oocytes. Biological Physics [physics.bio-ph]. Université Paris sciences et lettres, 2017. English. ⟨NNT : 2017PSLEE034⟩. ⟨tel-01804191⟩

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