Although cells in the body contain the same DNA content, they can display widely varying form and function among tissues. This comes about by differential gene regulation and by establishing a type of gene expression memory that is passed down during cell division to daughter cells. Gaydos et al. report that in nematodes, both sperm and oocytes transmit a memory of chromatin repression to embryos in the form of modified histones. During DNA replication, modified histones are passed to daughter chromatids to provide chromatin memory for a few cell divisions. Histone-modifying enzymes replenish histone modifications and provide long-term chromatin memory….
