design: Microglia nuclei were isolated from brain tissue crosslinked with paraformaldehyde by sorting using PU1 antibody and snap-frozen in liquid nitrogen. Nuclei were thawed, lysed, then sonicated and cleared by centrifugation. Supernatants were immunoprecipitated with antibodies bound to Protein A Dynabeads, washed 3 times with 3 buffers on ice. Libraries were prepared on beads using NEBNext Ultra II DNA Library Prep kit. Crosslinking was reversed by incubation at 65oC, digested with RNase A and proteinase K.Libraries were PCR-amplified for 14 cycles and size-selected for 225-350 bp fragments by gel extraction, then sequenced.