Phagocytosis reveals a reversible differentiated state early in the development of the mouse embryo.
Mural trophectoderm cells of the mouse embryo possess a phagocytic potential as early as 3.5 days post coitum (d.p.c.). This first differentiated function shows a graded variation along the embryonic-abembryonic axis, from a maximal activity in the non-dividing cells of the abembryonic pole to a complete lack of activity in the replicating polar trophectoderm overlying the inner cell mass (ICM). This pattern can be explained by a negative control exerted by the ICM. Addition of FGF4, a factor secreted by ICM cells, strongly inhibited phagocytosis while inducing resumption of DNA synthesis in mural trophectoderm cells, revealing a reversible, FGF4-dependent differentiation state. Under conditions in which a small cluster of mural trophectoderm cells (<10) had internalized large particles, these otherwise morphologically normal embryos could not implant in the uterus, indicating that cells at the abembryonic pole have a critical role in initiating the implantation process. At post-implantation stages (6.5-8.5 d.p.c.), the ectoplacental cone and secondary giant cells derived from the polar trophectoderm also contained active phagocytes, but at that stage, differentiation was not reversed by FGF4.
Rassoulzadegan
M
M
Unité 470 de l'INSERM, Faculté des Sciences, Université de Nice, France.
Rosen
B S
BS
Gillot
I
I
Cuzin
F
F
D000818:Animals; D001769:Blood; D002454:Cell Differentiation; D046508:Culture Techniques; D004475:Ectoderm; D010064:Embryo Implantation; D005314:Embryonic and Fetal Development / Q000276:immunology*; D005260:Female; D051519:Fibroblast Growth Factor 4; D005346:Fibroblast Growth Factors / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010587:Phagocytosis / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D016196:S Phase; D013234:Stem Cells / Q000166:cytology
C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; D011518:Proto-Oncogene Proteins; D005346:Fibroblast Growth Factors