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J Cell Biol 2018 Aug 06;2178:2661-2674. doi: 10.1083/jcb.201802080.
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F-Actin nucleated on chromosomes coordinates their capture by microtubules in oocyte meiosis.

Burdyniuk M , Callegari A , Mori M , Nédélec F , Lénárt P .

Capture of each and every chromosome by spindle microtubules is essential to prevent chromosome loss and aneuploidy. In somatic cells, astral microtubules search and capture chromosomes forming lateral attachments to kinetochores. However, this mechanism alone is insufficient in large oocytes. We have previously shown that a contractile F-actin network is additionally required to collect chromosomes scattered in the 70-µm starfish oocyte nucleus. How this F-actin-driven mechanism is coordinated with microtubule capture remained unknown. Here, we show that after nuclear envelope breakdown Arp2/3-nucleated F-actin "patches" form around chromosomes in a Ran-GTP-dependent manner, and we propose that these structures sterically block kinetochore-microtubule attachments. Once F-actin-driven chromosome transport is complete, coordinated disassembly of F-actin patches allows synchronous capture by microtubules. Our observations indicate that this coordination is necessary because early capture of chromosomes by microtubules would interfere with F-actin-driven transport leading to chromosome loss and formation of aneuploid eggs.

PubMed ID: 29903878
PMC ID: PMC6080919
Article link: J Cell Biol

Genes referenced: actr2 dnah3 LOC115925415 LOC590297 ran tubgcp2

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References [+] :
Almonacid, Actin-based spindle positioning: new insights from female gametes. 2014, Pubmed, Echinobase