An ultra-low-input native ChIP-seq protocol for genome-wide profiling of rare cell populations

The development of combined chromatin immunoprecipitation and next generation sequencing (ChIP-seq) technologies has enabled genome-wide epigenetic profiling of numerous cell lines and tissue types. A major limitation of ChIP-seq, however, is the large number of cells required to generate high quality datasets, precluding the study of rare cell populations. Here, we present an ultra-low-input micrococcal nuclease-based native ChIP (ULI-NChIP) and sequencing method, to generate genome-wide histone mark profiles with high resolution and reproducibility from as few as one thousand cells. Using ULI-NChIP, we generated high quality maps of several covalent histone marks from 10^3-10^6 embryonic stem cells. To further validate our procedure we demonstrate that genome-wide H3K27me3 profiles generated from 10^3 E13.5 primordial germ cells (PGCs) using ULI-NChIP-seq show high similarity to recently generated datasets using 50-180× more material, illustrating the utility of this method for generating high quality libraries with improved complexity from rare cell populations. Low input H3K9me3, H3K27me3 H3K4me3 and expression profiles in mouse ES cells.