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

The mechanistic target of rapamycin complex 2 (mTORC2) is essential for embryonic development but the underlying molecular mechanisms remain unclear. Here we show that disruption of mTORC2 in human embryonic stem cells (hESCs) considerably alters the balance of Rho/Rac signaling and reduces cell adhesion. Although these changes have no clear effect on their self-renewal and the expression of pluripotent markers, they significantly impede BMP-induced activation of canonical WNT genes, leading to impaired mesendoderm differentiation. Direct activation of the downstream WNT pathway by inhibiting GSK3 dramatically improves mesendoderm differentiation in mTORC2-deficient hESCs. Our studies uncover a new mechanism by which mTORC2 regulates cell fate determination and link the intercellular contacts with the activation of WNT genes. To investigate the function of mTORC2 in the regulation of embryonic development and cell fate determination, we disrupted RICTOR gene in human embryonic stem cells (hESCs) by CRISPR/Cas9. We then performed differential expression analysis using RNA-seq from two WT and two KO hESC lines.