Function and differential regulation of the alpha 6 integrin isoforms during parietal endoderm differentiation

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Biology

Background:

• F9 embryonal carcinoma cells differentiate into parietal endoderm (PE) or visceral endoderm (VE) upon retinoic acid treatment.
• Beta 1 integrins mediate cell-extracellular matrix interactions crucial for PE differentiation and migration.
• Integrin alpha 6 beta 1 is a major laminin receptor in F9 cells and PE cells.

Purpose of the Study:

• Investigate the expression pattern and function of integrin alpha 6 beta 1 during F9 cell differentiation into VE and PE.
• Determine the role of different alpha 6 integrin isoforms in F9 cell differentiation and motility.

Main Methods:

• Immunofluorescent staining and immunoprecipitation to analyze alpha 6 protein levels.
• Reverse transcription-PCR to study alpha 6 mRNA isoforms (alpha 6A and alpha 6B).
• Cell adhesion, migration assays, and pulse-chase experiments to assess protein function and stability.

Main Results:

• Alpha 6 beta 1 protein significantly decreases during F9 cell differentiation into VE and PE, while alpha 6 mRNA levels remain constant.
• A switch occurs from predominantly alpha 6B to increased alpha 6A mRNA and protein in differentiating PE cells.
• Alpha 6A localizes to focal contacts in PE cells, correlating with increased cell motility.

Conclusions:

• Down-regulation of alpha 6 beta 1 during F9 differentiation is post-transcriptional.
• The switch to the alpha 6A isoform and its localization are critical for PE cell motility.
• Distinct functions of alpha 6A and alpha 6B integrin isoforms are implicated in cell differentiation and migration.