Engineered Multivalent Sensors to Detect Coexisting Histone Modifications in Living Stem Cells

Area of Science:

• Epigenetics and Molecular Biology
• Cell Biology
• Developmental Biology

Background:

• Chromatin states, defined by histone post-translational modifications (PTMs), regulate key cellular processes like gene expression and differentiation.
• Understanding the subnuclear organization and dynamics of these chromatin states is crucial but limited by the lack of suitable live-cell detection tools.

Purpose of the Study:

• To develop genetically encoded probes for detecting and monitoring specific chromatin states in live cells.
• To investigate the subnuclear organization and dynamics of bivalent chromatin, a PTM pattern linked to pluripotency in embryonic stem cells (ESCs).

Main Methods:

• Engineered genetically encoded chromatin-sensing multivalent probes (cMAPs) targeting bivalent chromatin.
• Utilized synthetic nucleosomes with defined PTMs for probe optimization.
• Applied cMAPs in live ESCs to visualize chromatin organization and dynamics.

Main Results:

• cMAPs selectively detected bivalent chromatin in live ESCs.
• Demonstrated that bivalent chromatin is organized into discrete subnuclear foci or clusters.
• Showcased cMAPs' ability to monitor the dynamic loss of bivalency in response to epigenetic modulators.

Conclusions:

• cMAPs provide a novel and versatile platform for real-time monitoring of chromatin state dynamics in live cells.
• The findings offer new insights into the subnuclear organization of bivalent chromatin.
• cMAPs can facilitate the study of epigenetic regulation and pluripotency.