Specifying the Anterior Primitive Streak by Modulating YAP1 Levels in Human Pluripotent Stem Cells.

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Molecular Genetics

Background:

• Primitive streak (PS) specification is crucial for directing human embryonic stem cell (hESC) differentiation into mesendodermal lineages.
• Understanding the transcription networks governing anterior (APS) and posterior (PPS) PS cell differentiation is essential for precise stem cell manipulation.
• The role of the Hippo pathway effector YAP1 in PS specification remains incompletely understood.

Purpose of the Study:

• To elucidate the role of YAP1 in regulating the differentiation of anterior primitive streak (APS) cells from hESCs.
• To investigate the potential of inhibiting YAP1 to direct hESC differentiation towards specific mesendodermal subpopulations.
• To explore therapeutic strategies for generating APS-derived lineages, including cardiomyocytes, with improved fidelity.

Main Methods:

• Utilized YAP1 knockout (YAP1-/-) hESCs to assess gene induction in response to ACTIVIN.
• Employed dasatinib, a C-SRC/YAP1 inhibitor, for transient treatment of wild-type hESCs.
• Analyzed the differentiation potential of treated hESCs into APS-derived endoderm and cardiac mesoderm.

Main Results:

• YAP1 deficiency (YAP1-/-) led to the predominant induction of APS genes in hESCs stimulated with ACTIVIN.
• YAP1 acts as a master regulator, repressing ACTIVIN-driven APS gene expression in hESCs.
• Transient inhibition of YAP1 in wild-type hESCs with dasatinib promoted efficient differentiation into APS-derived endoderm and cardiac mesoderm, yielding functional cardiomyocytes without cytoskeletal defects.

Conclusions:

• YAP1 is a critical repressor of APS gene induction during hESC differentiation.
• A combination of ACTIVIN and a YAP1 inhibitor (dasatinib) provides an effective method for generating APS cells.
• This approach has significant implications for directed differentiation of hESCs and induced pluripotent stem cells into specific mesendodermal lineages for regenerative medicine.