Concanavalin A Acts as a Factor in Establishing the Dorso‐Ventral Gradient in the Ventral Mesoderm of Newt Gastrula Embryos¹

Abstract

Con A induced dorsal differentiation in the ventral mesoderm of Cynops gastrula embryo. This process apparently requires a certain amount of Con A to be internalized as supported by the following evidence: 1) Oligomannose‐type oligosaccharide, a potent inhibitor of Con A, considerably inhibited dorsalization of ventral mesoderm by Con A. The incorporation of 125I‐Con A into the ventral mesoderm was greatly inhibited by this sugar. 2) Sepharose‐immobilized Con A did not dorsalize the ventral mesoderm. Con A‐induced dorsalization was found to be concentration‐dependent. Microautoradiograms of 125I‐Con A‐treated ventral mesoderm suggest that the target site (some receptor molecules) of Con A exists inside the cell. Con A is the first pure substance reported to mimic the two properties of the organizer—neural induction of the competent ectoderm and dorsalization of the ventral mesoderm. In neural induction, Con A acts on the cell surface, while Con A apparently needs to be internalized to trigger dorsal differentiation. Interestingly, Con A‐dorsalized ventral mesoderm acquired the neural inducing function of the organizer within the early phase of dorsalization.

In vitroControl of Embryonic Axis Formation by Activin A, Concanavalin A, and Retinoic Acid in Xenopus laevis

“…The same molecule was later found to dorsalize Cynops ventral marginal zone (VMZ) explants. The VMZ explants differentiated into blood cells, pronephros, muscle, and notochord depending on the concentrations of Con A added (Diaz et al, 1990). In the present study, the activin-treated Xenopus animal caps fated to differentiate into ventral mesoderm were also dorsalized by the addition of Con A (series I).…”

“…They are secreted by the dorsal mesoderm before and during gastrulation, and can regulate neural induction and dorsalization of ventral mesoderm explants like Spemann's organizer (Lamb et al, 1993;Sasai et al, 1995Sasai et al, , 1996Piccolo et al, 1996;Zimmerman et al, 1996). Although concanavalin A (Con A) is not an endogenous factor, it also induces anterior neural tissues in animal cap explants (Takata et al, 1981(Takata et al, , 1984Grunz, 1985) and dorsalizes ventral mesoderm explants in Cynops embryos (Diaz et al, 1990). One of the candidates for the M agent, activin, is known to induce mesodermal tissues along the D-V axis in a dose-dependent manner (Asashima et al, 1990;Green and Smith, 1990;Ariizumi et al, 1991), however, its role in A-P patterning remains unclear.…”