Rspo2 antagonizes FGF signaling during vertebrate mesoderm formation and patterning

The fibronectin fibril matrix on the blastocoel roof of the Xenopus gastrula contains guidance cues that determine the direction of mesoderm cell migration. The underlying guidance-related polarity of the blastocoel roof is established in the late blastula under the influence of an instructive signal from the vegetal half of the embryo, in particular from the mesoderm. Formation of an oriented substratum depends on functional activin and FGF signaling pathways in the blastocoel roof. Besides being involved in tissue polarization, activin and FGF also affect fibronectin matrix assembly. Activin treatment of the blastocoel roof inhibits fibril formation, whereas FGF modulates the structure of the fibril network. The presence of intact fibronectin fibrils is permissive for directional mesoderm migration on the blastocoel roof extracellular matrix.

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FGF signaling induces mesoderm in members of Spiralia

10.1101/2020.08.13.249714 ◽

2020 ◽

Author(s):

Carmen Andrikou ◽

Andreas Hejnol

Keyword(s):

Gene Expression ◽

Mesoderm Induction ◽

Fgf Signaling ◽

Mesoderm Development ◽

Molecular Patterning ◽

Gene Expression Analyses ◽

Mesoderm Formation ◽

And Migration ◽

Mesoderm Patterning

AbstractFGF signaling is involved in mesoderm induction in deuterostomes, but not in flies and nematodes, where it has a role in mesoderm patterning and migration. However, comparable studies in other protostomic taxa are missing in order to decipher whether this mesoderm-inducing function of FGF extends beyond the lineage of deuterostomes. Here, we investigated the role of FGF signaling during mesoderm development in three species of lophophorates, a clade within the protostome group Spiralia. Our gene expression analyses show that the molecular patterning of mesoderm development is overall conserved between brachiopods and phoronids, but the spatial and temporal recruitment of transcription factors differs significantly. Moreover, inhibitor experiments demonstrate that FGF signaling is involved in mesoderm formation, morphogenetic movements of gastrulation and posterior axial elongation. Our findings suggest that the inductive role of FGF in mesoderm possibly predates the origin of deuterostomes.

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Molecular identification of spadetail: regulation of zebrafish trunk and tail mesoderm formation by T-box genes

Development ◽

10.1242/dev.125.17.3379 ◽

1998 ◽

Vol 125 (17) ◽

pp. 3379-3388 ◽

Cited By ~ 22

Author(s):

K.J. Griffin ◽

S.L. Amacher ◽

C.B. Kimmel ◽

D. Kimelman

Keyword(s):

Transcription Factor ◽

Genetic Model ◽

Zebrafish Embryos ◽

Fibroblast Growth ◽

Fgf Signaling ◽

T Box ◽

Tail Development ◽

No Tail ◽

Mesoderm Formation ◽

Complementary Actions

Inhibition of fibroblast growth factor (FGF) signaling prevents trunk and tail formation in Xenopus and zebrafish embryos. While the T-box transcription factor Brachyury (called No Tail in zebrafish) is a key mediator of FGF signaling in the notochord and tail, the pathways activated by FGF in non-notochordal trunk mesoderm have been uncertain. Previous studies have shown that the spadetail gene is required for non-notochordal trunk mesoderm formation; spadetail mutant embryos have major trunk mesoderm deficiencies, but relatively normal tail and notochord development. We demonstrate here that spadetail encodes a T-box transcription factor with homologues in Xenopus and chick. Spadetail is likely to be a key mediator of FGF signaling in trunk non-notochordal mesoderm, since spadetail expression is regulated by FGF signaling. Trunk and tail development are therefore dependent upon the complementary actions of two T-box genes, spadetail and no tail. We show that the regulatory hierarchy among spadetail, no tail and a third T-box gene, tbx6, are substantially different during trunk and tail mesoderm formation, and propose a genetic model that accounts for the regional phenotypes of spadetail and no tail mutants.

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