library_construction_protocol: Posterior limb bud tissue containing the ZPA region from E11.5 mouse embryos was dissected and manually disassociated followed by snap freezing. Library construction was performed using the Omni-ATAC-seq protocol (Buenrostro et al., 2013, 2015), with an adjusted lysis step and transposition buffer based on Omni-ATAC protocol (Corces et al., 2017).