Sebox regulates mesoderm formation in early amphibian embryos.
BACKGROUND
Mix/Bix genes are important regulators of mesendoderm formation during vertebrate embryogenesis. Sebox, an additional member of this gene family, has been implicated in endoderm formation during early embryogenesis in zebrafish. However, it remains unclear whether Sebox plays a unique role in early Xenopus embryos.


RESULTS
In this study, we provide evidence that Sebox is uniquely required for the formation of mesoderm during early Xenopus embryogenesis. Sebox is dynamically expressed in the involuted mesoderm during gastrulation. It is activated by Nodal/Activin signaling and modulated by zygotic Wnt/β-catenin signaling. Overexpression of Sebox perturbs movements during convergent extension and inhibits the expression of mesodermal, but not endodermal, genes induced by Nodal/Activin signaling. Depletion of Sebox using a specific morpholino increases the expression of noncanonical wnt5a, wnt5b, and wnt11b. Depletion of Sebox also up-regulates the expression of pcdh8.2, a paraxial mesoderm-specific protocadherin, in a Wnt11B-dependent manner. Sebox morphants display reduced development of the head and notochord.


CONCLUSIONS
Our findings illustrate that Sebox, a unique member of the Mix/Bix gene family, functions downstream of Nodal/Activin signaling and is required for the proper expression of noncanonical Wnt ligands and the normal development of mesoderm in Xenopus.
MOE Key Laboratory of Protein Sciences, Tsinghua University School of Life Sciences, Beijing, China.
Geng
G
Chen
MOE Key Laboratory of Protein Sciences, Tsinghua University School of Life Sciences, Beijing, China.
Renbo
R
Tan
MOE Key Laboratory of Protein Sciences, Tsinghua University School of Life Sciences, Beijing, China.
Qinghua
Q
Tao
D028341:Activins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018076:DNA, Complementary / Q000378:metabolism; D005775:Gastrula / Q000502:physiology; D054262:Gastrulation; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology*; D017403:In Situ Hybridization; D008024:Ligands; D008648:Mesoderm / Q000502:physiology*; D055457:Nodal Protein / Q000378:metabolism; D000091363:Protocadherins; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins / Q000235:genetics / Q000502:physiology*
D015820:Cadherins; D018076:DNA, Complementary; D018398:Homeodomain Proteins; D008024:Ligands; D055457:Nodal Protein; C117635:Pcdh8 protein, Xenopus; D000091363:Protocadherins; D051153:Wnt Proteins; D029867:Xenopus Proteins; D028341:Activins
PAPC; Wnt11; Xenopus; mix-like genes; noncanonical Wnt