Cell cycle regulators control mesoderm specification in human pluripotent stem cells

Abstract

Mesoderm is one of the three germ layers produced during gastrulation from which muscle, bones, kidneys and the cardiovascular system originate. Understanding the mechanisms controlling mesoderm specification could be essential for a diversity of applications, including the development of regenerative medicine therapies against diseases affecting these tissues. Here, we use human pluripotent stem cells (hPSCs) to investigate the role of cell cycle in mesoderm formation. For that, proteins controlling G1 and G2/M cell cycle phases were inhibited during differentiation of hPSCs into lateral plate, cardiac and presomitic mesoderm using small molecules or by conditional knock down. These loss of function experiments revealed that CDKs and pRb phosphorylation are necessary for efficient mesoderm formation in a context-dependent manner. Further investigations showed that inhibition of the G2/M regulator CDK1 decreases BMP signaling activity specifically during lateral plate mesoderm formation while reducing FGF/ERK1/2 activity in all mesoderm subtypes. Taken together, our findings reveal that cell cycle regulators direct mesoderm formation by controlling the activity of key developmental pathways.