Blastomeres of the mouse embryo lose totipotency after the fifth cleavage division: expression of Cdx2 and Oct4 and developmental potential of inner and outer blastomeres of 16- and 32-cell embryos.
Sixteen inner or outer blastomeres from 16-cell embryos and 32 inner or outer blastomeres from 32-cell embryos (nascent blastocysts) were reaggregated and cultured in vitro. In 24 h old blastocysts developed from blastomeres derived from 16-cell embryos the expression of Cdx2 protein was upregulated in outer cells (new trophectoderm) of the inner cells-derived aggregates and downregulated in inner cells (new inner cell mass) of the external cells-derived aggregates. After transfer to pseudopregnant recipients blastocysts originating from both inner and outer blastomeres of 16-cell embryo developed into normal, fertile mice, but the implantation rate of embryos formed from inner cell aggregates was lower. The aggregates of external blastomeres derived from 32 cell embryo usually formed trophoblastic vesicles accompanied by vacuolated cells. In contrast, the aggregates of inner blastomeres quickly compacted but cavitation was delayed. Although in the latter embryos the Cdx2 protein appeared in the new trophectoderm within 24 h of in vitro culture, these embryos formed only very small outgrowths of Troma1-positive giant trophoblastic cells and none of these embryos was able to implant in recipient females. In separate experiment we have produced normal and fertile mice from 16- and 32-cell embryos that were first disaggregated, and then the sister outer and inner blastomeres were reaggregated at random. In blastocysts developed from aggregates, within 24 h of in vitro culture, the majority of inner and outer blastomeres located themselves in their original position (internally and externally), which implies that in these embryos development was regulated mainly by cell sorting.
Suwińska
Aneta
A
Department of Embryology, Institute of Zoology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Poland.
Czołowska
Renata
R
Ozdzeński
Wacław
W
Tarkowski
Andrzej K
AK
D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis; D001757:Blastomeres / Q000145:classification / Q000166:cytology* / Q000502:physiology; D000071616:CDX2 Transcription Factor; D002449:Cell Aggregation / Q000502:physiology; D002452:Cell Count; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation / Q000379:methods; D003433:Crosses, Genetic; D046149:Embryo Culture Techniques; D010064:Embryo Implantation / Q000502:physiology; D004624:Embryo Transfer; D047108:Embryonic Development / Q000502:physiology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D050814:Octamer Transcription Factor-3 / Q000096:biosynthesis*; D017440:Photoperiod; D039901:Totipotent Stem Cells / Q000166:cytology* / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis*
D000943:Antigens, Differentiation; D000071616:CDX2 Transcription Factor; C487514:Cdx2 protein, mouse; D018398:Homeodomain Proteins; D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse; D014157:Transcription Factors