Assembly of tight junctions during early vertebrate development

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• Tight junctions are essential for embryonic patterning and tissue organization.
• Understanding the precise molecular mechanisms of tight junction biogenesis during early cleavage stages is crucial.

Purpose of the Study:

• To investigate and compare the mechanisms of tight junction biogenesis in cleaving mouse and Xenopus eggs.
• To elucidate the roles of cell polarity, gene expression, and specific proteins in junction assembly.

Main Methods:

• Comparative analysis of tight junction formation in mouse and Xenopus embryos.
• Examination of cell polarity establishment, membrane constituent delivery, and gene expression programs.
• Investigation of cadherin adhesion and occludin post-translational modification in relation to junction assembly.

Main Results:

• Tight junction assembly is initiated post-polarity establishment in both species.
• Cadherin adhesion is permissive for tight junction construction exclusively in mouse embryos.
• Occludin modification and membrane delivery, regulated by delayed ZO-1 alpha(+)isoform expression in mice, are key for tight junction completion and blastocoel cavitation.

Conclusions:

• Distinct molecular pathways govern tight junction biogenesis in mouse and Xenopus early development.
• Differential roles of cadherins and specific temporal expression of ZO-1 isoforms are critical for species-specific junction formation and embryonic development.
• These findings provide insights into the regulation of epithelial sealing and blastocoel formation.