library_construction_protocol: The ATAC-seq protocol was performed as previously described (Janes et  al. 2018 eLife). Briefly, worms were ground in Egg buffer (25mM HEPES pH 7.3, 118mM NaCl, 48mM KCl, 2mM CaCl2, 2mM MgCl2) and dounced to obtain cell nuclei. Nuclei were then resuspended in Tagmentation buffer and treated with the Tn5 enzyme (Illumina Nextera kit). Tagmented DNA was amplified using the Nextera kit protocol, and the amplified libraries were size selected using AMPure beads to recover fragments between 150 and 500pb and sequenced.