Anteroposterior neural tissue specification by activin-induced mesoderm

Area of Science:

• Developmental biology
• Embryology
• Molecular signaling

Background:

• Activin, a TGF-β superfamily member, induces mesodermal and neural tissues in Xenopus animal caps.
• Activin acts as a morphogen, with dose-dependent effects on dorsoventral axis patterning.
• Previous studies suggested neural induction by activin might be an indirect effect of mesodermal signaling.

Purpose of the Study:

• To directly demonstrate that induced mesoderm signals to uninduced ectoderm to form neural tissues.
• To investigate if activin concentration determines the anteroposterior properties of induced mesoderm.
• To explore the relationship between anteroposterior and dorsoventral patterning signals.

Main Methods:

• Xenopus laevis animal cap explants were treated with varying concentrations of activin.
• Cell mixing experiments were used to infer signaling pathways.
• Analysis of gene expression markers for mesodermal and neural tissues, and anteroposterior positional values.

Main Results:

• Direct evidence confirmed that induced mesoderm signals to uninduced ectoderm to generate neural tissues.
• Activin dose was found to control the anteroposterior positional value of induced mesoderm.
• Lower activin doses induced posterior mesodermal markers, while higher doses induced anterior markers, including neuroinductive properties.

Conclusions:

• Activin dose is critical for both dorsoventral and anteroposterior patterning of induced mesoderm in Xenopus.
• The findings provide insights into the mechanisms of axis formation and tissue patterning during embryonic development.
• This study clarifies the role of mesodermal signaling in neural induction and axis patterning.