Mesodermal induction in early amphibian embryos by activin A (erythroid differentiation factor)

Abstract

Recently the mesoderm-inducing effects of the transforming growth factor β (TGF-β) family of proteins have been widely examined. In an attemt to elucidate the functions of these proteins, porcine inhibin A and activin A (erythroid differentiation factor; EDF) were examined. Treatment of explants with activin A led to differentiation of mesodermal derivatives such as mesenchyme, notochord, blood cells and muscle, but inhibin A had a much lesser effect. The mesodermal differentiation induced by activin A was also comfirmed by analyses using a polyclonal antibody against muscle myosin. By indirect immunofluorescence analysis, the differentiation of muscle blocks was observed in the activin-A-treated explants, whereas no differentiation was observed in inhibin-A-treated and control explants. These findings confirm that this protein of the TGF-β family has mesoderm-inducing ability.

Endoplasmic reticulum stress induced by tunicamycin disables germ layer formation in Xenopus laevis embryos

“…As mesoderm is induced by the activin/nodal signaling pathway (Asashima et al, 1990;Smith et al, 1990;Tiedemann et al, 1992;Agius et al, 2000), we further tested if TM treatment had any influence on the activity of activin A in mesoderm induction using animal cap assays. Embryos were treated with 2 g/ml TM from 2-cell stage till stage 8.5.…”

Regulation of the Lim‐1 gene is mediated through conserved FAST‐1/FoxH1 sites in the first intron

“…In vivo, the importance of the nodal subfamily in gene regulation in early development is well established (Schier and Shen, 2000;Whitman, 2001), but a role for activin remains uncertain. Originally recognized as a mesoderm inducer (Smith et al, 1990;Asashima et al, 1990), activin played a large part in the study of early development in subsequent years. Although activin-like protein has been reported to be present in the early Xenopus embryo (Asashima et al, 1991), direct evidence for its involvement in embryogenesis has been difficult to obtain.…”

“…An effective system for the study of transcriptional regulation of Xlim-1 is provided by Xenopus animal explants, which respond to inducing factors such as activin by activation of mesodermal genes including Xlim-1 (Smith, 1987;Smith et al, 1990;Asashima et al, 1990;Taira et al, 1992;reviewed in Dawid, 1994). This system allows us to isolate the activin/nodal response of the Xlim-1 gene from other regulatory inputs, which seemed desirable as this gene is expressed at later stages in complex patterns, presumably necessitating a variety of regulatory inputs (Taira et al, 1992(Taira et al, , 1994aKaravanov et al, 1996;Hayes et al, 2001).…”

In vitro organogenesis from undifferentiated cells in Xenopus

“…Several research groups have identified activin and homologues thereof as factors that induce all mesodermal tissue types in the animal cap assay (Asashima et al, 1989(Asashima et al, , 1990aSmith et al, 1990;Sokol et al, 1990;van den Eijnden-Van Raaij et al, 1990). Activin, which is one of the transforming growth factor ␤ (TGF-␤) family proteins, stimulates the activin/Nodal signal pathway, one of the key signaling pathways in embryonic development.…”