NOTCH activation interferes with cell fate specification in the gastrulating mouse embryo

Abstract

NOTCH signalling is an evolutionarily conserved pathway involved in intercellular communication essential for cell fate choices during development. Although dispensable for early aspects of mouse development, canonical RBPJ-dependent NOTCH signalling has been shown to influence lineage commitment during embryonic stem cell (ESC) differentiation. NOTCH activation in ESCs promotes the acquisition of a neural fate, whereas its suppression favours their differentiation into cardiomyocytes. This suggests that NOTCH signalling is implicated in the acquisition of distinct embryonic fates at early stages of mammalian development. In order to investigate in vivo such a role for NOTCH signalling in shaping cell fate specification, we use genetic approaches to constitutively activate the NOTCH pathway in the mouse embryo. Early embryonic development, including the establishment of anterior-posterior polarity, is not perturbed by forced NOTCH activation. By contrast, widespread NOTCH activity in the epiblast triggers dramatic gastrulation defects. These are fully rescued in a RBPJ-deficient background. Epiblast-specific NOTCH activation induces acquisition of neurectoderm identity and disrupts the formation of specific mesodermal precursors including the derivatives of the anterior primitive streak, the mouse organiser. In addition, we show that forced NOTCH activation results in misregulation of NODAL signalling, a major determinant of early embryonic patterning. Our study reveals a previously unidentified role for canonical NOTCH signalling during mammalian gastrulation. It also exemplifies how in vivo studies can shed light on the mechanisms underlying cell fate specification during in vitro directed differentiation.

Notch Signaling Commits Mesoderm to the Cardiac Lineage

“…Aberrant activation of Notch signaling in cardiac precursors causes an enlargement of the left ventricle and may negatively impact maturation of the forming cardiomyocytes (Watanabe, 2006). While Notch activation in the cardiac lineage showed a hyperplasic phenotype, induction of Notch signaling in the epiblast has a negative overall impact on mesoderm specification and organization (Souilhol et al, 2015). Data from Xenopus suggests that active Notch signaling is important during a brief time window between gastrulation and differentiation, and that this timing acts to coordinate progenitor maintenance and differentiation.…”

“…Going forward, it will be important to dissect the detailed mechanism for how this occurs, and whether Notch signaling in the cardiac mesoderm is broadly cardiogenic. While studies have looked at the effects of Notch signaling on mouse development, these have largely been done using constitutive Notch activation (Souilhol et al, 2015;Watanabe, 2006). It would be of great interest to perturb Notch signaling within the early cardiac lineage in a temporally controlled and reversible manner, as has been done in other model organisms (Miazga and McLaughlin, 2009).…”

Modeling Mammalian Commitment to the Neural Lineage Using Embryos and Embryonic Stem Cells

“…The Notch signaling pathway has also been implicated in neurectoderm induction and regulation of neurectoderm proliferation and neuronal differentiation (Lowell et al, 2006; Souilhol et al, 2015; Boareto et al, 2017; Roese-Koerner et al, 2017). In the embryo, Notch works in conjunction with Fgf signaling from ~7.5 dpc to maintain the neuroepithelial pool, while blocking neurogenesis (Lowell et al, 2006; Souilhol et al, 2015). Notch is cleaved by γ-secretase after binding its reciprocal membrane receptor on a neighboring cell (Kopan, 2012).…”

Polycomb group RING finger protein 5 influences several developmental signaling pathways during the in vitro differentiation of mouse embryonic stem cells

“…Notch pathway affects the differentiation of all three germ‐layer cell types during gastrulation (Souilhol et al, 2015). Inactivation of Notch signaling promotes ESC differentiation towards the mesoderm fate and the subsequent cardiogenic potential (Jang et al, 2008).…”

“…Inactivation of Notch signaling promotes ESC differentiation towards the mesoderm fate and the subsequent cardiogenic potential (Jang et al, 2008). Activation of Epiblast‐specific Notch signaling causes the favor of neuroectoderm fate and the disruption of specific mesodermal precursor formation in the mouse embryo (Souilhol et al, 2015). Given the crucial contribution of Notch to neural and cardiac development, we speculate that the effect of Pcgf5 KO on mesodermal‐cardiac and ectodermal‐neural differentiation is possibly mediated by repression of Notch signaling genes.…”