UHRF2 mediates resistance to DNA methylation reprogramming in primordial germ cells [RNAseq_PGCs]

In mammals, primordial germ cells (PGCs) undergo global erasure of DNA methylation with delayed demethylation of germline genes and selective retention of DNA methylation at young retrotransposons. However, the molecular mechanisms of persistent DNA methylation in PGCs remain unclear. Here we report that resistance to DNA methylation reprogramming in PGCs requires UHRF2, the paralog of the DNMT1 cofactor UHRF1. PGCs from Uhrf2 knock-out mice show loss of retrotransposon DNA methylation, while DNA methylation is unaffected in somatic cells of Uhrf2-/- mice. Furthermore, Uhrf2-deficient PGCs show precocious demethylation of germline genes and overexpress meiotic genes in females. Overall design: To explore the dynamics of DNA methylation during epigenetic reprogramming in PGCs, we performed DNA methylation analysis by RRBS at all stages of PGC development in the mouse from E9.5 to E17.5. To study the role of Dnmt1 and Uhrf2 in PGCs, we performed DNA methylation analysis by RRBS in PGCs isolated from E13.5 embryos carrying a conditional knockout of Dnmt1 and PGCs isolated from Uhrf2-deficient and WT control E13.5 embryos. To expand our study of the role of Uhrf2, we also performed DNA methylation analysis by RRBS in Uhrf2-deficient and WT control E8.5 embryos, postnatal organs (brain, liver, heart) and spermatozoa. Finally, we studied the consequences of Uhrf2 deficiency on the transcriptome by performing RNA-seq in Uhrf2-deficient and WT control E8.5 embryos, and Uhrf2-deficient and WT control PGCs isolated from E13.5 embryos.