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XB-ART-56945
Cells January 1, 2020; 9 (5):

The Spindle Assembly Checkpoint Functions during Early Development in Non-Chordate Embryos.

Chenevert J , Roca M , Besnardeau L , Ruggiero A , Nabi D , McDougall A , Copley RR , Christians E , Castagnetti S .


Abstract
In eukaryotic cells, a spindle assembly checkpoint (SAC) ensures accurate chromosome segregation, by monitoring proper attachment of chromosomes to spindle microtubules and delaying mitotic progression if connections are erroneous or absent. The SAC is thought to be relaxed during early embryonic development. Here, we evaluate the checkpoint response to lack of kinetochore-spindle microtubule interactions in early embryos of diverse animal species. Our analysis shows that there are two classes of embryos, either proficient or deficient for SAC activation during cleavage. Sea urchins, mussels, and jellyfish embryos show a prolonged delay in mitotic progression in the absence of spindle microtubules from the first cleavage division, while ascidian and amphioxus embryos, like those of Xenopus and zebrafish, continue mitotic cycling without delay. SAC competence during early development shows no correlation with cell size, chromosome number, or kinetochore to cell volume ratio. We show that SAC proteins Mad1, Mad2, and Mps1 lack the ability to recognize unattached kinetochores in ascidian embryos, indicating that SAC signaling is not diluted but rather actively silenced during early chordate development.

PubMed ID: 32354040
PMC ID: PMC7290841
Article link: Cells
Grant support: [+]

Species referenced: Xenopus
Genes referenced: dnai1 fubp1 h2bc21 mad2l1 mxd1 neb nup153 rps27


Article Images: [+] show captions
References [+] :
Abrieu, Mps1 is a kinetochore-associated kinase essential for the vertebrate mitotic checkpoint. 2001, Pubmed, Xenbase