Cell commitment and gene expression in the axolotl embryo.

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• The somitic mesoderm in axolotl embryos undergoes commitment phases for muscle differentiation.
• Understanding the molecular events during this commitment is crucial for developmental biology.

Purpose of the Study:

• To investigate the molecular and structural changes during somitic mesoderm commitment in axolotl embryos.
• To determine the precise timing of alpha-actin synthesis and thin filament formation relative to commitment phases.

Main Methods:

• Analysis of actin isoform synthesis during axolotl embryonic development.
• Microscopic examination of thin filament and sarcomere formation in somitic mesoderm.
• Culture of isolated presumptive somitic mesoderm to assess autonomous differentiation.

Main Results:

• Alpha-actin synthesis and thin filament appearance coincide with the transition from reversible to irreversible commitment.
• Alpha-actin is specifically localized to somites and tailbud, regions forming myotomal muscles.
• Isolated somitic mesoderm autonomously synthesizes alpha-actin and forms sarcomeres, confirming intrinsic developmental capacity.

Conclusions:

• The commencement of alpha-actin synthesis is a key molecular event defining the irreversible commitment of axolotl somitic mesoderm to muscle.
• Early muscle structure, including thin filaments and sarcomeres, forms autonomously within the somitic mesoderm.
• This study provides insights into the temporal regulation of muscle differentiation in vertebrate embryos.