Regulation of neural induction by the Chd and Bmp-4 antagonistic patterning signals in Xenopus

The novel mammalian gene Crim1 encodes a transmembrane bound protein with similarity to the secreted bone morphogenetic protein (BMP) antagonists, vertebrate Chordin, and its Drosophila homologue short gastrulation. Crim1 is expressed in the neural tube in mouse in a restricted pattern, but its function in central nervous system development is largely unknown. We isolated the chicken Crim1 orthologue and analyzed its expression in the developing neural tube. Chicken CRIM1 shares strong homology to human/mouse CRIM1 and C. elegans CRIM1-like proteins. Crim1 is expressed in a similar but not identical pattern to that in the developing spinal cord of mouse, including the notochord, floor plate, motor neurons, and the roof plate. Unlike follistatin, a secreted inhibitor of BMPs, in ovo electroporation of CRIM1, as a full-length transmembrane bound or secreted ectodomain was not sufficient to disrupt early patterning of the neural tube. However, ectodomain CRIM1 overexpression leads to an approximate 50% decrease in populations of specific ventral neuronal populations, including ISL-1 ؉ motor neurons, CHX-10 ؉ V1, and EN-1 ؉ V2 interneurons. Developmental Dynamics 226:107-111, 2003.

Section: Introductionmentioning

confidence: 72%

In ovo electroporation of Crim1 in the developing chick spinal cord

Kolle

Jansen

Yamada

et al. 2002

“…To help clarify how FGF signaling affects organizer formation, we analyzed expression of the organizer genes goosecoid (gsc), chordin, xnr3, and noggin (Cho et al, 1991;Smith and Harland, 1992;Sasai et al, 1995;Smith et al, 1995) as well as otx2 and otx5 (Lamb et al, 1993;Vignali et al, 2000), which are expressed in the dorsal mesendoderm prior to expression in the anterior neural plate. Embryos were analyzed at the early gastrula stage.…”

Section: Fgf Signaling Is Essential For Establishment Of Paraxial Mesmentioning

confidence: 99%

“…Anti-sense RNA probes were made for the following transcripts: xbra (Smith et al, 1991); myoD (Hopwood et al, 1989); sox2 (Grammer et al, 2000); otx2 (Lamb et al, 1993); otx5 (Vignali et al, 2000); hoxB9 (Sharpe et al, 1987); gsc (Cho et al, 1991); myf5 (Hopwood et al, 1991); noggin (Smith and Harland, 1992); chordin (Sasai et al, 1995); xnr3 ; sox17 (Hudson et al, 1997); eomes (Ryan et al, 1996); VegT (Stennard et al, 1996); edd (Sasai et al, 1996); FGF4 (Isaacs et al, 1992); FGF8 (Fletcher et al, 2006).…”

Section: Whole Mount Rna In Situ Hybridizationmentioning

confidence: 99%

The role of FGF signaling in the establishment and maintenance of mesodermal gene expression in Xenopus

Fletcher

Harland

2008

FGF signaling is important for the formation of mesoderm in vertebrates, and when it is perturbed in Xenopus, most trunk and tail mesoderm fails to form. Here we have further dissected the activities of FGF in patterning the embryo by addressing its inductive and maintenance roles. We show that FGF signaling is necessary for the establishment of xbra expression in addition to its well-characterized role in maintaining xbra expression. The role of FGF signaling in organizer formation is not clear in Xenopus. We find that FGF signaling is essential for the initial specification of paraxial mesoderm but not for activation of several pan-mesodermal and most organizer genes; however, early FGF signaling is necessary for the maintenance of organizer gene expression into the neurula stage. Inhibition of FGF signaling prevents VegT activation of specific mesodermal transcripts. These findings illuminate how FGF signaling contributes to the establishment of distinct types of mesoderm.

“…In Drosophila, the BMP homologue Dpp is antagonized by a chordin homologue, short gastrulation (sog; Marques et al, 1997). The proteins are sufficiently conserved that they retain dorsalizing and ventralizing activities in cross-species expression experiments Sasai et al, 1995;Schmidt et al, 1995;Holley et al, 1995Holley et al, , 1996. Most exciting, from an evolutionary point of view, is that, whereas BMP is ventral and chordin dorsal, in flies, it is the other way around: Dpp is dorsal and sog is ventral.…”

Section: Morphogens In Vivo Part Ii: Fgfs and Bmpsmentioning

confidence: 99%

Morphogen gradients, positional information, and Xenopus: Interplay of theory and experiment

Green

2002

The idea of morphogen gradients has long been an important one in developmental biology. Studies with amphibians and with Xenopus in particular have made significant contributions to demonstrating the existence, identity, and mechanisms of action of morphogens. Mesoderm induction and patterning by activin, nodals, bone morphogenetic proteins, and fibroblast growth factors have been analyzed thoroughly and reveal recurrent and combinatorial roles for these protein growth factor morphogens and their antagonists. The dynamics of nodal-type signaling and the intersection of VegT and ␤-catenin intracellular gradients reveal detailed steps in early long-range patterning. Interpretation of gradients requires sophisticated mechanisms for sharpening thresholds, and the activin-Xbra-Gsc system provides an example of this. The understanding of growth factor signal transduction has elucidated growth factor morphogen action and provided tools for dissecting their direct longrange action and distribution. The physical mechanisms of morphogen gradient establishment are the focus of new interest at both the experimental and theoretical level. General themes and emerging trends in morphogen gradient studies are discussed.