GSE167984
Loss of SETD1B results in the redistribution of genomic H3K4me3 in the oocyte [RNA-seq]
Histone 3 lysine 4 trimethylation (H3K4me3) is an epigenetic mark found at active gene promoters and CpG islands. H3K4me3 is essential for mammalian development, yet mechanisms underlying its genomic targeting are poorly understood. H3K4me3 methyltransferases SETD1B and MLL2 are essential for oogenesis. We investigated changes in H3K4me3 in Setd1b conditional knockout (cKO) GV oocytes using ultra-low input ChIP-seq, in complement to DNA methylation and gene expression analysis. Setd1b cKO oocytes showed a redistribution of H3K4me3, with a marked loss at active gene promoters associated with downregulated gene expression. Remarkably, many regions gained H3K4me3 in Setd1b cKOs, in particular those that were DNA hypomethylated, transcriptionally inactive and CpG-rich. All of these are hallmarks of MLL2 targets; thus, loss of SETD1B appears to enable enhanced MLL2 activity. Our work reveals two distinct, complementary mechanisms of genomic targeting of H3K4me3 in oogenesis, with SETD1B linked to transcriptional activity and MLL2 to CpG content. Overall design: Single GV oocytes were collected from females with an oocyte conditional deletion of Setd1b using Gdf9-cre (Setd1b cKO) and females carrying floxed Setd1b (Setd1b WT) for single cell RNA-seq for four and three biological replicates, respectively.