Canonical Notch Signaling Is Dispensable for Early Cell Fate Specifications in Mammals

Abstract

Identifying mechanisms responsible for early cell fate specifications and formation of the three germ layers is a fundamental issue in developmental and evolutionary biology. The canonical Notch signaling pathway stimulated by Delta-and Jagged-like ligands is functionally conserved among the metazoa (2, 29) and is required for early cell fate specifications or the formation of germ layers in Caenorhabditis elegans (12, 41) and sea urchins (1, 43-45, 52) and for endoderm patterning in zebrafish (3, 21). Drosophila melanogaster (5, 6) and C. elegans (28) need maternal contributions of certain Notch pathway components for early development, while sea urchins (25) and zebrafish (11, 35, 53) apparently do not.

Regulation of Notch signaling by glycosylation

“…The phenotypes are cell-autonomous and highly characteristic of disrupted Notch signaling. Surprisingly, removal of Pofut1 in the 2-cell blastocyst has no consequences prior to gastrulation [39]. Interestingly, inactivation of the Golgi GDP-Fucose transporter is associated with leukocyte adhesion defects in humans [40] and in mice [41], and gives a mild, temperature-sensitive Notch phenotype in flies [42].…”

Evolutionary Origins of Notch Signaling in Early Development

“…By contrast, Notch signaling is not required in mouse (mammals) for the earliest cell fate specifications leading to the inner cell mass and trophectoderm, nor for the formation of the three germ layers or embryonic development to E8.0. 1 Because C. elegans, sea urchin and zebrafish use Notch signaling at different stages and in different ways for early cell specifications, we propose that a process of co-option occurred during divergent evolution from a common ancestor to allow these organisms to use Notch signaling for early cell fate determinations. This co-option event did not occur in mammals.…”

“…An outstanding question that we recently addressed was whether Notch signaling is required for early embryonic development or the formation of the three germ layers in mammals. 1 …”

Slc35c2 Promotes Notch1 Fucosylation and Is Required for Optimal Notch Signaling in Mammalian Cells

“…Ligand-dependent Notch Signaling Assays-Notch signaling co-culture assays were performed as previously described (13,14,40). Briefly, duplicate cell cultures were plated at 2 ϫ 10 5 cells per well of a six-well dish and, after ϳ24 h, were cotransfected using FuGENE 6 (Roche Applied Science) with 0.2 g of the Notch reporter plasmid TP-1 that carries eight copies of a RBP-J DNA binding sequence driving a firefly luciferase reporter gene (41), 0.05 g of pRL-TK, or 0.01 g of pRL-CMV Renilla luciferase (Promega, Madison, WI), and 1.5 g of pMIRB empty vector.…”