mTORC2-mediated cell-cell interactions promote BMP4-induced WNT activation and mesoderm differentiation

Area of Science:

• Stem cell biology
• Molecular mechanisms of development
• Cell signaling pathways

Background:

• The mechanistic target of rapamycin complex 2 (mTORC2) is crucial for embryonic development.
• The precise molecular mechanisms governing mTORC2's role in early development are not fully understood.
• Understanding mTORC2 function is key to deciphering developmental processes and potential therapeutic targets.

Purpose of the Study:

• To investigate the role of mTORC2 in human embryonic stem cell (hESC) self-renewal and differentiation.
• To elucidate the molecular pathways influenced by mTORC2 in hESCs.
• To identify how mTORC2 impacts cell adhesion and developmental signaling.

Main Methods:

• Disruption of mTORC2 signaling in hESCs.
• Analysis of Rho/Rac signaling dynamics.
• Assessment of E-cadherin expression and cell adhesion.
• Evaluation of pluripotent marker expression and self-renewal capacity.
• Mesoderm and endoderm differentiation assays using BMP4 and Activin.
• WNT pathway activation analysis and rescue experiments using a GSK3 inhibitor.

Main Results:

• mTORC2 disruption alters Rho/Rac signaling, reduces E-cadherin, and impairs cell adhesion in hESCs.
• Despite adhesion defects, mTORC2-deficient hESCs maintain self-renewal and pluripotency markers in MEF-CM with bFGF.
• Differentiation into mesoderm and endoderm is significantly impaired in mTORC2-deficient hESCs.
• Impaired differentiation is linked to reduced WNT activation, potentially mediated by cell-cell interactions.
• Direct WNT pathway activation via GSK3 inhibition restores mesendoderm differentiation.

Conclusions:

• mTORC2 plays a critical role in regulating hESC cell fate determination.
• Intercellular adhesion, modulated by mTORC2, is essential for activating canonical WNT genes.
• This study reveals a novel link between mTORC2, cell adhesion, and WNT signaling in embryonic development.