Approximately 30-50 ng of purified genomic DNA in 50 µl has been subject to sonication using the Bioruptor Pico (Diagenode) for 15 cycles of (30 ON; 90 OFF). Fragmentation patterns have been checked with the D1000HS Assay (Agilent Technologies) on a 4200 TapeStation. The volume of the fragmented DNA has been reduced to 20 µl using a Vacufuge (Eppendorf), then subject to bisulfite conversion using the EZ DNA Methylation-Lightning Kit (Zymo Research). The libraries have been prepared using the Accel-NGS Methyl kit (Swift Biosciences - now xGen Methyl-Seq Library Prep - IDT) according to the manufacturer's recommendations except a major modification.