Models of convergent extension during morphogenesis.

Area of Science:

• Developmental Biology
• Cell Biology
• Evolutionary Biology

Background:

• Convergent extension (CE) is a crucial collective cell movement in embryonic development, forming elongated tissues.
• Two primary mechanistic models of CE have been identified: the crawling mode and the contraction mode.

Purpose of the Study:

• To review and compare the crawling and contraction modes of convergent extension.
• To highlight differences in cytoskeletal behaviors and cell adhesion molecules between the two modes.
• To discuss upstream regulatory molecules involved in CE.

Main Methods:

• Comparative analysis of existing literature on CE mechanisms.
• Focus on cytoskeletal dynamics and cell adhesion molecule expression.
• Discussion of upstream regulatory pathways.

Main Results:

• The crawling mode, exemplified by notochord formation in Xenopus laevis, has been the long-standing model.
• The contraction mode, observed in Drosophila melanogaster germband extension, is now recognized as a conserved CE mechanism.
• Differences in cytoskeletal activity and cell adhesion distinguish these two modes.

Conclusions:

• Understanding the distinct mechanisms of CE (crawling vs. contraction) is key to comprehending collective cell regulation.
• Comparative studies across different model systems reveal conserved and divergent strategies in embryonic tissue elongation.