title: Orientation of mitotic spindles during the 8- to 16-cell stage transition in mouse embryos.
abstract: BACKGROUND
  Asymmetric cell divisions are involved in the divergence of the first two lineages of the pre-implantation mouse embryo. They first take place after cell polarization (during compaction) at the 8-cell stage. It is thought that, in contrast to many species, spindle orientation is random, although there is no direct evidence for this.
  
  
  RESULTS
  Tubulin-GFP and live imaging with a spinning disk confocal microscope were used to directly study spindle orientation in whole embryos undergoing the 8- to 16-cell stage transition. This approach allowed us to determine that there is no predetermined cleavage pattern in 8-cell compacted mouse embryos and that mitotic spindle orientation in live embryo is only modulated by the extent of cell rounding up during mitosis.
  
  
  CONCLUSIONS
  These results clearly demonstrate that spindle orientation is not controlled at the 8- to 16-cell transition, but influenced by cell bulging during mitosis, thus reinforcing the idea that pre-implantation development is highly regulative and not pre-patterned.
authors.affiliation: CNRS, UMR7622-Laboratoire de Biologie Cellulaire du Développement, Paris, France. nicolas.dard@upmc.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dard
authors.forename: Sophie
authors.initials: S
authors.lastname: Louvet-Vallée
authors.forename: Bernard
authors.initials: B
authors.lastname: Maro
mesh_terms: D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology* / Q000378:metabolism*; D047108:Embryonic Development; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008938:Mitosis; D008941:Spindle Apparatus / Q000378:metabolism*; D013997:Time Factors