In this issue of Cell, two studies from Jiang et al. (pp. 773–784) and Potok et al. (pp. 759–772) generate genome-wide methylome maps of zebrafish gametes and early embryos. Surprisingly, the sperm methylome remains largely unchanged until zygotic genome activation, and the oocyte undergoes a series of methylation-demethylation reprogramming cycles to ultimately match the patterns of sperm.
Question: How the piRNA dynamics co-incide with the methylation dynamics during MZT?