Transcription-driven DNA methylation setting on the mouse Peg3 locus.

Area of Science:

• Genetics
• Epigenetics
• Developmental Biology

Background:

• The mouse Peg3 domain's imprinting is regulated by the Peg3 differentially methylated region (DMR), which acquires maternal-specific DNA methylation during oogenesis.
• Understanding the mechanisms establishing this maternal methylation is key to deciphering imprinting control.

Purpose of the Study:

• To investigate the role of an oocyte-specific alternative promoter, U1, located upstream of the Peg3-DMR, in establishing maternal DNA methylation.
• To determine the impact of U1 deletion on Peg3 domain imprinting and gene expression.

Main Methods:

• Deletion of the oocyte-specific alternative promoter U1, located 20 kb upstream of the Peg3-DMR.
• Analysis of DNA methylation status of the Peg3-DMR in the generated mouse mutants.
• Quantification of imprinted gene expression levels (Peg3, Usp29, Zim1) in mutant offspring.
• Breeding experiments to assess potential sex-biased survival outcomes.

Main Results:

• Deletion of the U1 promoter completely abolished maternal-specific DNA methylation on the Peg3-DMR.
• Imprinted genes within the Peg3 domain exhibited biallelic expression in mutants with maternal transmission of the deletion.
• Significant alterations in gene expression were observed: 2-fold upregulation of Peg3 and Usp29, and downregulation of Zim1.
• Breeding studies revealed an under-representation of females among surviving mutants, suggesting a potential sex-biased outcome.

Conclusions:

• U1-driven transcription is essential for establishing oocyte-specific DNA methylation at the Peg3 domain.
• The U1 promoter plays a critical role in regulating the imprinting and expression of genes within the Peg3 domain.
• Biallelic expression of the Peg3 domain may contribute to sex-biased developmental outcomes.