Repeat DNA methylation is modulated by adherens junction signaling

Area of Science:

• Cell Biology
• Epigenetics
• Molecular Biology

Background:

• DNA methylation is crucial for gene transcription and heterochromatin formation, influencing cellular environmental interactions.
• Extracellular signals modulating DNA methylation distribution, particularly at repetitive elements, remain largely unknown.
• Investigating DNA methylation in live cells faces methodological challenges, especially for abundant repetitive elements.

Purpose of the Study:

• To uncover signaling pathways connecting chromatin modifications at repetitive elements to epithelial adherens junction integrity.
• To investigate how cell density influences DNA methylation patterns in live cells.
• To identify molecular players involved in relaying cell density signals to the nucleus.

Main Methods:

• Development and utilization of a CRISPR/dCas9 biosensor for live-cell monitoring of DNA methylation at human α-satellite repeats.
• Comparative analysis of α-satellite repeat methylation in confluent versus low-density breast epithelial cell monolayers.
• Comprehensive perturbation experiments to identify key molecular mediators.

Main Results:

• Reduced α-satellite repeat methylation and increased transcriptional activity observed in confluent cell monolayers compared to low-density cultures.
• E-cadherin, a junctional protein linking to the actin cytoskeleton, identified as a central mediator for signal relay to the nucleus.
• The identified pathway is impaired in cancer cells lacking E-cadherin and contact inhibition.

Conclusions:

• A novel signaling pathway links cell density, repetitive element methylation, and epithelial adherens junction integrity.
• E-cadherin plays a critical role in transmitting cell density information to the nucleus, affecting chromatin.
• Dysregulation of this pathway in cancer cells suggests its importance in maintaining epithelial tissue homeostasis.