At fertilization the sperm delivers to the embryo paternal genomic information, as well as epigenetic information such as those encoded in DNA methylation, post translational modifications of histones, and small RNAs. We are interested in evaluating the contribution of these epigenetic cues in the normal development of embryos, in particular in the regulation of gene expression and the establishment of early embryonic cell fate. Here we focus on H2AK119ub1, a histone modification associated with the polycomb repressive complex 1. We use the frog Xenopus laevis to generate embryos using sperm from which this histone modification was erased just prior to introduction into the egg. With this new assay we demonstrate that, in frogs, sperm derived H2AK119ub1 instructs egg factor mediated epigenetic remodelling of paternal chromatin and is required for embryonic development. Besides this functional evaluation in model organisms, we carried out epigenetic profiling of sperm in humans. We use a calibrated ChIP approach to identify human sperm genomic locations where modified histones have the required credentials for a role in embryos development

Jérôme Jullien is invited by Julie Cocquet.