Concentration-dependent inducing activity of activin A

Abstract

Human recombinant activin A, which is identical with erythroid differentiation factor (EDF), was tested for its mesoderm-inducing activity in concentrations from 0.3-50 ng/ml, using ectoderm of Xenopus late blastula (Stage 9) as the responding tissue. At a low concentration of activin A, blood-like cells, mesenchyme, and coelomic epithelium were induced; at a moderate concentration muscle and neural tissue, and at a high concentration notochord. Activin A thus induced all mesodermal tissues in a dose-dependent manner, such that a low dose induced ventral structures and a high dose induced dorsal structures. Activin may act as an intrinsic inducing molecule responsible for establishing the dorso-ventral axis in early Xenopus development.

Induction of tooth and eye by transplantation of activin A-treated, undifferentiated presumptive ectodermal Xenopus cells into the abdomen

“…Fertilized eggs were obtained from both male and female Xenopus laevis injected with 600 IU of gonadotropin (Gestron; Denka Seiyaku Co., Kawasaski, Japan) and their jelly coat were removed with Steinberg's solution containing 4.5% cysteine hydrochloride (pH 7.8) (Ariizumi et al, 1991). Animal cap sheets cut from stage-9 Xenopus embryos were dissociated in CMF-Steinberg's solution containing 0.1 % fatty acid-free bovine serum albumin (Sigma Chemical Co.).…”

Mechanisms of Egg Activation and Polyspermy Block in Amphibians and Comparative Aspects with Fertilization in Other Vertebrates

“…Hematopoietic induction has been studied in explants of blastula animal cap in Xenopus (Ariizumi et al, 1991;Green et al, 1990). In response to basic fibroblast growth factor (bFGF), bone morphogenetic proteins (BMPs), or activin A, a lot of "blood-like cells" were induced.…”

Dorsal midline fate in Drosophila embryos requires twisted gastrulation, a gene encoding a secreted protein related to human connective tissue growth factor.

“…Two possible mechanisms to accomplish this are a differential responsiveness to a graded diffusible morphogen (e.g., a gradient of DPP) or a combinatorial input of mul-twisted gastrulation affects dorsal midline cell fate tiple signaling molecules (e.g., DPP + TSG = dorsal midline; DPP only= dorsal ectoderm). For example, in animal cap explants from Xenopus embryos, different concentrations of activin induce at least three different tissue types (Ariizumi et al 1991) suggesting a graded diffusible morphogen model. Alternatively, it has been found that activin and FGF can act together to specify cell fates in animal cap explants from Xenopus embryos (Green et al 1992), as activin and fibroblast growth factor (FGF) together at low concentrations result in levels of muscle induction that neither signaling molecule alone could produce at that low concentration.…”