Mesoderm Induction in Amphibians: the Role of TGF-β2-Like Factors

Abstract

Mesoderm induction in the amphibian embryo can be studied by exposing animal region explants (destined to become ectoderm) to appropriate stimuli and assaying the appearance of mesodermal products like alpha-actin messenger RNA. Transforming growth factor beta 2 (TGF-beta 2), but not TGF-beta 1, was active in alpha-actin induction, while addition of fibroblast growth factor had a small synergistic effect. Medium conditioned by Xenopus XTC cells (XTC-CM), known to have powerful mesoderm-inducing activity, was shown to contain TGF-beta-like activity as measured by a radioreceptor binding assay, colony formation in NRK cells, and growth inhibition in CCL64 cells. The activity of XTC-CM in mesoderm induction and in growth inhibition of CCL64 cells was inhibited partially by antibodies to TGF-beta 2 but not by antibodies to TGF-beta 1. Thus, a TGF-beta 2-like molecule may be involved in mesoderm induction.

Transforming growth factor-beta 1 (TGF-β1)- and β2-like activities in malignant pleural effusions caused by malignant mesothelioma or primary lung cancer

“…In the mouse embryo, TGF-/32 mRNA and its protein were found primarily in mesoderm-derived organs [6]. Rosa et al reported that TGF-/32-like activity augments mesoderm induction [26]. TGF-^1 is also important for the development of mesoderm-derived organs [27].…”

Morphoregulation

“…Some induction events occur by exchange of diffusible signals or morphogens, as shown for TGF p-like molecules and activin (Rosa et al, 1988;Smith, 1987). Others may occur only by direct cell-cell interaction as seen in "bride of sevenless'' interactions in Drosophila eyes (Kramer et al, 1991).…”

“…gene expression (Gurdon, 1987;Rosa et al, 1988;Smith, 1987), the isolation of cell adhesion molecules (Edelman and Crossin, 19911, new knowledge of the mode of action of homeotic genes (Gehring, 1987;Gaunt et al, 1988), and increasing insight into the molecular factors governing cell division, cell shape and motion, and cell death (Nurse, 1991;Borneus, 1991;Bock and O'Connor, 1987). It is not too early in any attempt to understand morphogenesis to ask how all of these matters relate to one another.…”

A novel, activin-inducible, blastopore lip-specific gene of Xenopus laevis contains a fork head DNA-binding domain.

“…They were treated with FGF, activin, or cycloheximide according to Rosa et al (1988) and Rosa (1989). We have used the following factor concentrations: 50 pM activin; 100 ng/ml of bFGF.…”