Sebox regulates mesoderm formation in early amphibian embryos

Abstract

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/b-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 upregulates 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.

The miR-125 family is an important regulator of the expression and maintenance of maternal effect genes during preimplantational embryo development

“…Therefore, further studies should determine whether Sebox represents a novel transcription factor and clarify mutual functional interactions between Sebox and its target genes. In mice, Sebox has recently been shown to affect both early oogenesis in the fetus and early embryogenesis, and it has also been reported to affect mesoderm formation in early amphibian embryos [17,19,39,40]. In this study, we provide the first report that Sebox, both mRNA and protein, is expressed in mESCs.…”

A catalog of Xenopus tropicalis transcription factors and their regional expression in the early gastrula stage embryo

“…Most notable among these include sebox and mxtx1 , which are strongly expressed in both vegetal endoderm and throughout the marginal zone (but not animally), and therefore may be involved in mesendoderm specification. X. laevis sebox is expressed in the mesoderm ( Chen et al, 2015 ), but has not been reported in the vegetal endoderm, which is notorious for signal underrepresentation in in situ hybridization experiments. Zebrafish mxtx1 and 2 are expressed in the extra-embryonic yolk syncytial layer ( Hirata et al, 2000 ) but this gene has not been reported in Xenopus until the current study.…”