Samples were washed in PBS, then lysed in 10 mM Tris-HCL 0.1% IGEPAL buffer, followed by transposition reaction using Nextera DNA Transposase for 30 minutes at 37 degrees. DNA was then isolated using Qiagen MinElute PCR purification. Sequencing libraries were generated as described (Buenrostro Nat Methods 2013) by PCR with Nextera index sequences.