Bromodomain‐dependent stage‐specific male genome programming by Brdt

Male germ cell differentiation is a highly regulated multistep process initiated by the commitment of progenitor cells into meiosis and characterized by major chromatin reorganizations in haploid spermatids. We report here that a single member of the double bromodomain BET factors, Brdt, is a master regulator of both meiotic divisions and post‐meiotic genome repackaging. Upon its activation at the onset of meiosis, Brdt drives and determines the developmental timing of a testis‐specific gene expression program. In meiotic and post‐meiotic cells, Brdt initiates a genuine histone acetylation‐guided programming of the genome by activating essential genes and repressing a ‘progenitor cells’ gene expression program. At post‐meiotic stages, a global chromatin hyperacetylation gives the signal for Brdt's first bromodomain to direct the genome‐wide replacement of histones by transition proteins. Brdt is therefore a unique and essential regulator of male germ cell differentiation, which, by using various domains in a developmentally controlled manner, first drives a specific spermatogenic gene expression program, and later controls the tight packaging of the male genome.