Epigenetic reprogramming of imprinting at meiosis

Abstract

In mammals, genomic imprinting results from different sets of epigenetic marks that distinguish the parental origins of loci in the progeny. Epigenetic reprogramming of genomic imprinting is necessary to establish a totipotent cell state. The consecutive erasure of parental epigenetic marks and the deposition of new marks occurs alongside major life stage transitions including gametogenesis and fertilization. However, despite occurring concomitantly with gametogenesis, the role of meiosis in epigenetic reprogramming has received little attention. To address this question, we use the model bryophyte Marchantia polymorpha. Following the haploid reproductive phase of this land plant, the expression of the paternal genome is silenced by the histone modification H3K27me3 in the short-lived diploid embryo. We show that imprinting is erased during meiosis, which occurs separately from gametogenesis and fertilization in Marchantia. The epigenetic reprogramming initiated during meiosis is completed in the meiotic spores where the chromatin landscape of the next haploid generation is established de novo. Hence, our findings illustrate a potential role for meiosis in epigenetic reprogramming that may be generalized to other sexually reproducing species.