ATAC-seq was performed using freshly harvested WT and Slc31a1 cKO BMSCs. Approximately 50,000 viable cells per sample were washed with cold PBS and lysed in ice-cold nuclei isolation buffer. Nuclei were collected by centrifugation and subjected to Tn5 transposition in transposition buffer at 37°C for 30 minutes. Tagmented DNA was then purified for library amplification. Tagmented DNA generated by Tn5 transposition was amplified by PCR using indexed primers. Libraries were purified using AMPure XP beads and assessed for size distribution and concentration using an Agilent Bioanalyzer or equivalent platform. Qualified ATAC-seq libraries were sequenced on an Illumina platform to generate paired-end reads.