Abstract
Gastrulation drives the establishment of three germ layers and embryonic axes during frog embryonic development. Mesodermal cell fate specification and morphogenetic movements are vital factors coordinating gastrulation, which are regulated by numerous signaling pathways, such as the Wnt (Wingless/Integrated), Notch, and FGF (Fibroblast growth factor) pathways. However, the coordination of the Notch and FGF signaling pathways during gastrulation remains unclear. We identified a novel helix–loop–helix DNA binding domain gene (Hes5.9), which was regulated by the FGF and Notch signaling pathways during gastrulation. Furthermore, gain- and loss-of-function of Hes5.9 led to defective cell migration and disturbed the expression patterns of mesodermal and endodermal marker genes, thus interfering with gastrulation. Collectively, these results suggest that Hes5.9 plays a crucial role in cell fate decisions and cell migration during gastrulation, which is modulated by the FGF and Notch signaling pathways.
Highlights
In a systematic screen for differentially expressed transcripts under the influence of FGF signaling in Xenopus tropicalis embryos, we isolated a novel transcript during gastrulation
The phylogenetic analysis further revealed that Hes5.9 was closely related to Hes5.7 (Hes9.1) and Hes5 subfamily members (Figure 1B), which are the downstream genes of Notch signaling
According to the gene locus, Hes5.9 localizes in the Hes5.3 cluster, consisting of Hes5.3–Hes5.10, Hes5.9 was suggested to be possibly synchronously regulated by the Notch signaling
Summary
That fertilized eggs are developed to shaped individuals, rather than mounds of pluripotent cells, is largely due to a short period termed gastrulation, which comprises a great many critical events, such as morphogenetic movements, specification of body axes and germ layer, and body plan establishment. By temporal-spatial coordination of cell specification and dynamic cell movement, a three germ layer body plan is established, accompanied by embryonic axis formation, during gastrulation. Gastrulation plays pivotal roles during embryogenesis and organogenesis. Research from represented model organisms has revealed that numerous signaling pathways, such as the Wnt (Wingless/Integrated), FGF (Fibroblast growth factor), BMP (Bone morphogenetic protein), Notch, and TGF-β (Transforming growth factor-beta)/Nodal signaling pathways [1,2], are involved in mesoderm specification and movement. The molecular mechanisms and temporal-spatial orchestrations of these signaling still remain largely obscure
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