Development 133, 319-329 doi:10.1242/dev.02210
The Vg1-related protein Gdf3 acts in a Nodal signaling pathway in the pre-gastrulation mouse embryo
Canhe Chen1,*, Stephanie M. Ware2,*, Akira Sato3, Dianne E. Houston-Hawkins4, Raymond Habas3, Martin M. Matzuk4,5,6, Michael M. Shen1,† and Chester W. Brown4,7,†
The formation of the anterior visceral endoderm (AVE) in thepre-gastrulation mouse embryo represents a crucial event in patterning of the anterior-posterior axis. Here, we show that the transforming growth factor (Tgf ) family member Gdf3 (growth-differentiation factor 3), a close relative of Xenopus Vg1, resembles the Tgf ligand Nodal in both its signaling activity and its role in AVE formation in vivo. Thus, in cell culture, Gdf3 signaling requires theEGF-CFC co-receptor Cripto and can be inhibited by Lefty antagonists. In Xenopus embryos, Gdf3 misexpression results in secondary axis formation, and induces morphogenetic elongation and mesendoderm formation in animal caps. In mouse embryos, Gdf3 is expressed in the inner cell mass and epiblast, and null mutants frequently exhibit abnormal formation or positioning of the AVE. This phenotypecorrelates with defects in mesoderm and deﬁnitive endoderm formation, as well as abnormal Nodal expression levels. Our ﬁndings indicate that Gdf3 acts in a Nodal-like signaling pathway in pre-gastrulation development, and provide evidence for the functional conservation of Vg1 activity in mice.
KEY WORDS: Tgf signaling, EGF-CFC proteins, Anterior visceral endoderm, Mesendoderm formationINTRODUCTION A key event in formation of the anteroposterior axis of the mouse embryo is the induction of the anterior visceral endoderm (AVE), a specialized population of cells within the extra-embryonic visceral endoderm that overlies and patterns the adjacent epiblast (reviewed by Lu et al., 2001; Rossant and Tam, 2004). The AVE is formed in the most distal region of the post-implantation egg cylinder at5.5 days post coitum (dpc), but then translocates to the prospective anterior side by 6.0 dpc (Rivera-Perez et al., 2003; Srinivas et al., 2004; Thomas et al., 1998), prior to the onset of gastrulation. Both formation as well as movement of the AVE require activity of the Nodal signaling pathway, whereas the AVE itself produces Nodal antagonists that are essential for patterning of the anteriorepiblast (Brennan et al., 2001; Ding et al., 1998; Perea-Gomez et al., 2002; Yamamoto et al., 2004). As a consequence, anti-Nodal signals from the distal visceral endoderm become opposed to Nodal signals from the proximal epiblast, and together pattern the anteroposterior (AP) axis following movement of the AVE. The molecular regulation of AVE induction and Nodal signaling activities is therefore ofcentral importance for AP axis patterning in the mammalian embryo. However, despite many recent advances in understanding early embryo patterning, the function of one of the ﬁrst Tgf superfamily members to be implicated in vertebrate development has remained
Center for Advanced Biotechnology and Medicine and Department of Pediatrics, University of Medicine and Dentistry of New Jersey-Robert WoodJohnson Medical School, Piscataway, NJ 08854, USA. 2Department of Pediatrics, Cincinnati Children’s Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA. 3Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA. 4Department of Molecular and Human Genetics, BaylorCollege of Medicine, Houston, TX 77030, USA. 5Department of Pathology, Baylor College of Medicine, Houston, TX 77030, USA. 6Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA. 7Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
*These authors contributed equally to this work Authors for correspondence (e-mail:...