Int. J. Dev. Biol. 54: 81 - 92 (2010)

https://doi.org/10.1387/ijdb.082837mf

Vol 54, Issue 1

Zygotic VegT is required for Xenopus paraxial mesoderm formation and is regulated by Nodal signaling and Eomesodermin

Original Article | Published: 25 November 2009

Masakazu Fukuda¹, Shuji Takahashi², Yoshikazu Haramoto³, Yasuko Onuma⁴, Yeon-Jin Kim⁵, Chang-Yeol Yeo⁵, Shoichi Ishiura^1,2,6 and Makoto Asashima*^3,6,7

¹Department of Biological Sciences, Graduate School of Science, ²Center for Structuring Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, ³ICORP Organ Regeneration Project, Japan Science and Technology Agency (JST), ⁴Network for Life Science Education, The University of Tokyo, Japan, ⁵Department of Life Science and Division of Life and Pharmaceutical Sciences, Ewha Women’s University, Korea, ⁶Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo and ⁷Organ Development Research Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Japan

Abstract

The T-box gene VegT plays a crucial role during mesendoderm specification of the amphibian embryo. While the function of maternal VegT (mVegT) has been extensively investigated, little is known about the function and transcriptional regulation of zygotic VegT (zVegT). In the present study, we used comparative genomics and a knockdown experiment to demonstrate that zVegT is the orthologous gene of zebrafish Spadetail/Tbx16 and chick Tbx6L/Tbx6, and has an essential role in paraxial mesodermal formation. zVegT knockdown embryos show several defects in the patterning of trunk mesoderm, such as abnormal segmentation of somites, a reduction in muscle, and the formation of an abnormal mass of cells at the tail tip. We also identified the cis-regulatory elements of zVegT that are necessary and sufficient for mesoderm-specific expression. These cis-regulatory elements are located in two separate upstream regions of zVegT, corresponding to the first intron of mVegT. The results of in vitro binding and functional assays indicate that Forkhead box H1 (FoxH1) and Eomesodermin (Eomes) are the trans-acting factors required for zVegT expression. Our results highlight the essential role of zVegT in organization of paraxial mesoderm, and reveal that zVegT is regulated by a coherent feedforward loop of Nodal signaling via Eomes.

Keywords

VegT, eomesodermin, nodal, paraxial mesodermal formation, coherent feedforward loop