A CRISPR screen identifies genes controlling Etv2 threshold expression in murine hemangiogenic fate commitment

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Molecular Biology

Background:

• The precise upstream regulation of Etv2, a key transcription factor for hematopoietic and endothelial cell generation, remains unclear.
• Understanding hemangiogenesis (the development of blood and blood vessel cells) requires identifying its upstream regulators.

Purpose of the Study:

• To elucidate the molecular mechanisms controlling hemangiogenesis and the upstream regulators of Etv2.
• To identify factors critical for the specification of hemangiogenic progenitors from mouse embryonic stem cells.

Main Methods:

• Utilized mouse embryonic stem cell lines with Brachyury, Etv2, or Scl reporters.
• Performed genome-wide CRISPR screening and transcriptome analysis of developing hemangiogenic progenitors.
• Tracked developmental routes of hemangiogenic progenitors.

Main Results:

• Identified the forkhead transcription factor Foxh1 as crucial for FLK1+ mesoderm formation.
• Demonstrated that hemangiogenic fate specification is dependent on a threshold of Etv2 expression.
• Showed that VEGF-FLK1 signaling plays an instructive role in promoting Etv2 threshold expression.

Conclusions:

• Foxh1, partly via Eomes, is critical for specifying hemangiogenic progenitors.
• Hemangiogenesis is regulated by a threshold-dependent mechanism involving Etv2 expression levels.
• VEGF-FLK1 signaling is essential for initiating hemangiogenesis by modulating Etv2 expression.