Nodal cis-regulatory elements reveal epiblast and primitive endoderm heterogeneity in the peri-implantation mouse embryo

• Published in: Developmental biology 2011-01, Vol.349 (2), p.350-362
• Main Authors: Granier, Céline, Gurchenkov, Vasily, Perea-Gomez, Aitana, Camus, Anne, Ott, Sascha, Papanayotou, Costis, Iranzo, Julian, Moreau, Anne, Reid, John, Koentges, Georgy, Sabéran-Djoneidi, Délara, Collignon, Jérôme
• Format: Article
• Language: English
• Subjects: Activins; Activins - metabolism; Animals; beta-Galactosidase; Binding Sites; Binding Sites - genetics; blastocyst; Computational Biology; Conserved Sequence; Conserved Sequence - genetics; Development Biology; DNA Primers; DNA Primers - genetics; Embryo, Mammalian; Embryo, Mammalian - embryology; Embryo, Mammalian - metabolism; Endoderm; Endoderm - metabolism; Endoderm - physiology; Epiblast; Forkhead Transcription Factors; Forkhead Transcription Factors - genetics; Forkhead Transcription Factors - metabolism; Gene Expression Regulation, Developmental; Gene Expression Regulation, Developmental - genetics; Gene Expression Regulation, Developmental - physiology; Genotype; Germ Layers; Germ Layers - metabolism; Germ Layers - physiology; Heterogeneity; Homeodomain Proteins; Homeodomain Proteins - metabolism; In Situ Hybridization; Life Sciences; Likelihood Functions; Mice; Mice, Transgenic; Microscopy, Confocal; Models, Genetic; Mouse blastocyst; mutants; Nanog; Nanog Homeobox Protein; Nodal; Nodal Protein; Nodal Protein - genetics; Nodal Protein - metabolism; Primitive endoderm; Signal Transduction; Signal Transduction - genetics; Signal Transduction - physiology; transgenes
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2010.10.036

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. ► Ancestral mechanisms of Nodal regulation are conserved in the mouse blastocyst. ► Canonical Wnt signaling is activated in the epiblast before implantation. ► Activin/Nodal signaling is independent of Nodal and FoxH1 in mouse blastocysts. ► Activin/Nodal signaling is inversely correlated to Nanog presence in late blastocysts.