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Development. 2019 Jan 2;146(1). pii: dev169664. doi: 10.1242/dev.169664.

A cargo model of yolk syncytial nuclear migration during zebrafish epiboly.

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Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.
Department of Cellular and Physiological Sciences, Life Sciences Institute, Vancouver Campus, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
Cellular and Molecular Neurobiology, Zoological Institute, TU Braunschweig, Spielmannstr. 7, 38106 Braunschweig, Germany.
Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada


In teleost fish, the multinucleate yolk syncytial layer functions as an extra-embryonic signaling center to pattern mesendoderm, coordinate morphogenesis and supply nutrients to the embryo. External yolk syncytial nuclei (e-YSN) undergo microtubule-dependent movements that distribute the nuclei over the large yolk mass. How e-YSN migration proceeds, and the role of the yolk microtubules, is not understood, but it is proposed that e-YSN are pulled vegetally as the microtubule network shortens from the vegetal pole. Live imaging revealed that nuclei migrate along microtubules, consistent with a cargo model in which e-YSN are moved down the microtubules by direct association with motor proteins. We found that blocking the plus-end directed microtubule motor kinesin significantly attenuated yolk nuclear movement. Blocking the outer nuclear membrane LINC complex protein Syne2a also slowed e-YSN movement. We propose that e-YSN movement is mediated by the LINC complex, which functions as the adaptor between yolk nuclei and motor proteins. Our work provides new insights into the role of microtubules in morphogenesis of an extra-embryonic tissue and further contributes to the understanding of nuclear migration mechanisms during development.


Epiboly; LINC complex; Microtubule; Yolk syncytial layer; Yolk syncytial nuclei; Zebrafish

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Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

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