Mesoderm and endoderm internalization in the Xenopus gastrula

Area of Science:

• Developmental Biology
• Cellular Biology
• Embryology

Background:

• Xenopus gastrulation involves intricate morphogenetic processes for mesoderm and endoderm internalization.
• The vegetal half of the gastrula features a multilayered wall crucial for these movements.
• While bottle cell formation is mechanistically understood, other deep-layer processes require further analysis.

Purpose of the Study:

• To elucidate the diverse morphogenetic processes underlying Xenopus gastrulation.
• To analyze cell migration and rearrangement mechanisms in deep embryonic layers.
• To understand the interplay of apical and deep layer processes in shaping the embryo.

Main Methods:

• Observation of cell behaviors including migration, protrusion formation, and rearrangement.
• Analysis of epithelial-type processes like bottle cell formation and cell intercalation.
• Investigating cell migration modes (mesenchymal vs. amoeboid) and their roles.

Main Results:

• Mesoderm internalization occurs via involution driven by cell-on-cell migration.
• Endoderm internalization involves vegetal rotation of cell masses.
• Cells exhibit mesenchymal migration with protrusions or amoeboid migration resembling free bottle cells.
• Differential cell migration leads to intercalation and convergent extension.
• Combined processes result in dorsal invagination, involution, vegetal rotation, and blastopore constriction.

Conclusions:

• Xenopus gastrulation is a multilayered process integrating apical and deep layer cell behaviors.
• The study provides insights into the mechanistic basis of gastrulation movements.
• Speculation on the evolutionary derivation of these movements from simpler invertebrate systems is proposed.