In the today's (April 17th) issue of Cell, D. J. Katz et al. from Emory University reported their experimental results which reveal that the demethylase LSD1/KDM1 plays a crucial role in reprogramming the zygote of C. elegans back to a developmental ground state. The investigators found that in mutant C. elegans for spr-5, an orthologof LSD1, each succeding generation of C. elegans became more sterile. The researchers found that the mutation correlated with misregulation of expressed genes involved in spermatogenesis. The data suggested that this epigenetic event was transgenerational which resulted in accumulation of modifed histone H# on the lysine 4 (H3K4me2). The author concluded that H3K4me2 can serve as stable epigenetic memory, and "erasure (demethylation) by LSD1/KDM1 in the germline prevents inappropriate transmission of this epigenetic memory from one generation to the next." The authors conclude that their study results provide some mechanistic insights into epigenetic reprogramming following fertilization and stripping the zygote's genome of these epigenetic modifications back to its ground state.