QSER1 protects DNA methylation valleys from de novo methylation

Area of Science:

• Epigenetics and Gene Regulation
• Mammalian Development
• Genomics

Background:

• DNA methylation is vital for mammalian development, with its dysregulation linked to pathologies.
• While DNA methylation enzymes are known, their cooperative mechanisms in regulating the methylation landscape are unclear.
• Understanding these regulatory networks is crucial for deciphering developmental processes and disease etiology.

Purpose of the Study:

• To identify novel regulators of DNA methylation using a genome-wide screening approach.
• To elucidate the function of the uncharacterized gene QSER1 in maintaining DNA methylation patterns.
• To investigate the interaction between QSER1 and other epigenetic modifiers, such as TET1.

Main Methods:

• Genome-wide CRISPR-Cas9 screening in human embryonic stem cells.
• Utilized a knockin DNA methylation reporter system for efficient screening.
• Performed genetic and biochemical assays to validate interactions and functions.

Main Results:

• Identified QSER1 as a top hit, revealing its critical role in regulating DNA methylation.
• Demonstrated that QSER1 acts as a guardian of bivalent promoters and poised enhancers, particularly in DNA methylation valleys.
• Showed genetic and biochemical evidence of QSER1 cooperating with TET1.

Conclusions:

• QSER1 is a novel and essential regulator of the DNA methylome.
• QSER1 and TET1 collaborate to protect developmental gene expression from aberrant de novo methylation by DNMT3.
• This interaction is critical for maintaining cellular identity and preventing pathological conditions associated with epigenetic dysregulation.