Henri van Kruistum is a Ph.D. candidate at Wageningen University where he is working on the genomics of placenta evolution in livebearing fish

Allele-specific DNA methylation has been considered of vital importance for several processes such as X-chromosome inactivation, and placenta and brain functioning, but its intricacies have been studied mainly in mammals. Here, we present a method to detect allele-specific methylation directly based on Oxford Nanopore sequencing. We apply this method to four individuals of the live-bearing fish species Poeciliopsis gracilis to gain insight in the occurrence of allele-specific methylation in its genome, as well as the inheritance of methylated alleles from parent to offspring. We show that allele-specific methylation is widespread in the genome of P. gracilis, and the inheritance of methylated alleles is non-random, but instead relies on parent-of-origin.