Mesendoderm Induction and Reversal of Left–Right Pattern by Mouse Gdf1, a Vg1-Related Gene

Abstract

TGFbeta signals play important roles in establishing the body axes and germ layers in the vertebrate embryo. Vg1 is a TGFbeta-related gene that, due to its maternal expression and vegetal localization in Xenopus, has received close examination as a potential regulator of development in Xenopus, zebrafish, and chick. However, a mammalian Vg1 ortholog has not been identified. To isolate mammalian Vg1 we screened a mouse expression library with a Vg1-specific monoclonal antibody and identified a single cross-reactive clone encoding mouse Gdf1. Gdf1 is expressed uniformly throughout the embryonic region at 5.5-6.5 days postcoitum and later in the node, midbrain, spinal cord, paraxial mesoderm, lateral plate mesoderm, and limb bud. When expressed in Xenopus embryos, native GDF1 is not processed, similar to Vg1. In contrast, a chimeric protein containing the prodomain of Xenopus BMP2 fused to the GDF1 mature domain is efficiently processed and signals via Smad2 to induce mesendoderm and axial duplication. Finally, right-sided expression of chimeric GDF1, but not native GDF1, reverses laterality and results in right-sided Xnr1 expression and reversal of intestinal and heart looping. Therefore, GDF1 can regulate left-right patterning, consistent with the Gdf1 loss-of-function analysis in the mouse (C. T. Rankin, T. Bunton, A. M. Lawler, and S. J. Lee, 2000, Nature Genet. 24, 262-265) and a proposed role for Vg1 in Xenopus. Our results establish that Gdf1 is posttranslationally regulated, that mature GDF1 activates a Smad2-dependent signaling pathway, and that mature GDF1 is sufficient to reverse the left-right axis. Moreover, these findings demonstrate that GDF1 and Vg1 are equivalent in biochemical and functional assays, suggesting that Gdf1 provides a Vg1-like function in the mammalian embryo.

BMP/SMAD1 signaling sets a threshold for the left/right pathway in lateral plate mesoderm and limits availability of SMAD4

“…1G,H), as in the chick (Yokouchi et al 1999). FGF-8 and other TGF␤ family members including ACTIVIN and GDF1 are capable of inducing Nodal and Pitx2 when overexpressed in the right LPM (Wall et al 2000). GDF-1 is an essential cofactor for NODAL in laterality signals (Rankin et al 2000;Tanaka et al 2007).…”

BMP signalling in craniofacial development

“…Ventral neural tube, midbrain, paraxial mesoderm (Rankin et al, 2000, Wall et al, 2000 Defects in left-right axis formation (Rankin et al, 2000) Gdf5 (CDMP1) Joint, tooth attachment apparatus and pulp (Nakashima et al, 1998, Sena et al, 2003, Settle et al, 2003 Naturally occurred mutation in mice: brachypod syndrome, (Storm et al, 1994, Storm andKingsley, 1996) Related disorders: loss function mutation associated with Brachychod in mice, chondrodysplasia Grebe type (OMIM, 200700) and Hunter-Thompson type of acromesomelic dysplasia (OMIM, 201250) in human.…”

Vg1 is an essential signaling molecule inXenopusdevelopment

“…Although the role of zebrafish DVR1 has not been established, overexpression experiments suggest that chick Vg1 is important in primitive streak formation in chick (Shah et al, 1997;Skromne and Stern, 2002). By contrast, a loss-of-function mutant of mouse Gdf1 has normal germ layer specification, is viable to E14.5 and has leftright axis abnormalities (Rankin et al, 2000;Wall et al, 2000). In Xenopus, previous loss-of-function studies used a dominant-negative approach (Joseph and Melton, 1998).…”