Method for accurate epigenome profiling using a few hundred cells and its applications

Difficulties to accurately map epigenomes in a few cells sorted or dissected from tissues have hampered our understanding of how chromatin modification regulates development and diseases. Despite recent progress, all reported chromatin-immunoprecipitation-based deep sequencing (ChIP-seq) methods have not achieved high quality mapping of rare cell populations. We report Recovery via Protection (RP)-ChIP-seq and favored amplification RP-ChIP-seq (FARP-ChIP-seq) for as few as 500 cells with superior quality compared to all reported techniques to date. FARP-ChIP-seq accurately mapped histone H3 lysine 4 trimethylation (H3K4me3) and H3K27me3 in long-term hematopoietic stem cells (LT-HSCs), short-term HSCs (ST-HSCs), and multi-potent progenitors (MPPs) sorted from one mouse. These high quality datasets not only implicate genes involved in HSC differentiation but also demonstrate a general lack of H3K4me3/H3K27me3 bivalency on hematopoietic genes in HSCs. Thus the method offers accurate mapping for fewest cells. Overall design: two H3K4me3 replications for mESC, two to three replications of H3K4me3 and H3K27me3 for LT-HSC, ST-HSC and MPP, 2 replicates of H3K4me3 for young and old lens