Transcriptome profiling of wild type and Tet1-null primordial germ cells (PGC) by Bisulfite-seq. Mus musculus

Purpose: To investigate the effect of Tet1 depletion on global DNA methylation, we performed whole-genome bisulfite sequencing (WGBS). Methods: Starting with as little as 1400-5251 manually micro-dissected PGCs, we used an ultra-low input method, Tn5mC-seq. Results: We generated 945 million reads for Tet1Gt/Gt PGCs and 302 million reads for wild-type PGCs. We obtained 14-16 million CpG sites per genotype at 1.76-2.66x genome coverage, which enables a comprehensive view of genome-wide DNA methylation patterns in E13.5 PGCs. PGCs are almost completely unmethylated genome-wide. Loss of Tet1 led to a subtle increase of methylation level in various genomic elements including promoters, exons, introns and repetitive elements in Tet1Gt/Gt PGCs (p<0.01). Local analysis identified 4,337 differentially methylated regions (DMRs) between Tet1-/- PGCs and wild-type cells. These DMRs are associated with 5,261 genes, among which 271 genes also exhibited differential gene expression and enriched for the cell cycle pathway (FDR=0.02). Conclusions: This result revealed that demethylation of certain set of cell cycle genes is largely abolished in the Tet1-/- PGCs. Overall design: Genome-wide methylation profiles of primordial germ cells derived from the wild type (WT) and Tet1-null female embryos at E13.5 were generated by whole genome bisulfite sequencing using Illumina Hiseq.