Nodal cis-regulatory elements reveal epiblast and primitive endoderm heterogeneity in the peri-implantation mouse embryo.
Nodal, a secreted factor known for its conserved functions in cell-fate specification and the establishment of embryonic axes, is also required in mammals to maintain the pluripotency of the epiblast, the tissue that gives rise to all fetal lineages. Although Nodal is expressed as early as E3.5 in the mouse embryo, its regulation and functions at pre- and peri-implantation stages are currently unknown. Sensitive reporter transgenes for two Nodal cis-regulatory regions, the PEE and the ASE, exhibit specific expression profiles before implantation. Mutant and inhibitor studies find them respectively regulated by Wnt/β-catenin signaling and Activin/Nodal signaling, and provide evidence for localized and heterogeneous activities of these pathways in the inner cell mass, the epiblast and the primitive endoderm. These studies also show that Nodal and its prime effector, FoxH1, are not essential to preimplantation Activin/Nodal signaling. Finally, a strong upregulation of the ASE reporter in implanting blastocysts correlates with a downregulation of the pluripotency factor Nanog in the maturing epiblast. This study uncovers conservation in the mouse blastocyst of Wnt/β-catenin and Activin/Nodal-dependent activities known to govern Nodal expression and the establishment of polarity in the blastula of other deuterostomes. Our results indicate that these pathways act early on to initiate distinct cell-specification processes in the ICM derivatives. Our data also suggest that the activity of the Activin/Nodal pathway is dampened by interactions with the molecular machinery of pluripotency until just before implantation, possibly delaying cell-fate decisions in the mouse embryo.
Université Paris-Diderot, CNRS, Institut Jacques Monod, UMR 7592, Development and Neurobiology programme, F-75013 Paris, France.
Céline
C
Granier
Vasily
V
Gurchenkov
Aitana
A
Perea-Gomez
Anne
A
Camus
Sascha
S
Ott
Costis
C
Papanayotou
Julian
J
Iranzo
Anne
A
Moreau
John
J
Reid
Georgy
G
Koentges
Délara
D
Sabéran-Djoneidi
Jérôme
J
Collignon
D028341:Activins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019295:Computational Biology; D017124:Conserved Sequence / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004622:Embryo, Mammalian / Q000196:embryology* / Q000378:metabolism; D004707:Endoderm / Q000378:metabolism / Q000502:physiology*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D005838:Genotype; D005855:Germ Layers / Q000378:metabolism / Q000502:physiology*; D018398:Homeodomain Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D016013:Likelihood Functions; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008957:Models, Genetic; D000071317:Nanog Homeobox Protein; D055457:Nodal Protein / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D001616:beta-Galactosidase
D017931:DNA Primers; D051858:Forkhead Transcription Factors; C491117:Foxh1 protein, mouse; D018398:Homeodomain Proteins; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse; D055457:Nodal Protein; C526008:Nodal protein, mouse; D028341:Activins; D001616:beta-Galactosidase