Live imaging of acentrosomal microtubule dynamics controlling early mammalian development

Zenker J1, White M1, Templin R2, Parton R2, Thorn-Seshold O3, Alvarez Y1, Gasnier M1, Bissiere S1, Biro M4 and Plachta N1

  1. IMCB, A*STAR Singapore.
  2. IMB, Centre for Microscopy and Microanalysis, University of Queensland, Australia.
  3. Department for Pharmacy, Center for Drug Research, Ludwig-Maximilians University, Munich, Germany.
  4. EMBL Australia, Single Molecule Science node, School of Medical Sciences, UNSW, Sydney, Australia.

The spatial and temporal configuration of the microtubule cytoskeleton is pivotal for a cell’s function. Whereas in most animal cells the centrosome is the primary microtubule organizing center (MTOC), the regulation of microtubule growth and dynamics in the preimplantation mouse embryo lacking centrosomes remained elusive. Using live imaging, we discovered a new site of non-centrosomal microtubule nucleation required for mammalian embryogenesis. Instead of undergoing stereotypical abscission, the cytokinetic bridge is maintained during interphase and transformed into a non-centrosomal MTOC. Accumulation of the microtubule minus-end protein CAMSAP3 enables the nucleation of non-centrosomal microtubules directing intracellular transport and the formation of the pluripotent inner cell mass. Moreover, acentrosomale and anastral spindles of the embryo establish a polar microtubule network at the end of cell division excluding F-actin from the apical cortex of outer cells. The resulting apical actin rings expand towards cell-cell junctions, zipper and seal the embryo to allow blastocyst cavitation.