Histone marks retained during epigenetic reprogramming and their roles essential for fish early development

SummaryReprograming of epigenetic modifications after fertilization is required for proper embryonic development and cell differentiation. However, histone modifications that escape reprogramming in non-mammalian vertebrates and their potential functional roles are poorly understood. Here, we quantitatively analyzed histone modification dynamics during reprogramming in Japanese Killifish, medaka (Oryzias latipes) embryos, and revealed that H3K27ac, H3K27me3 and H3K9me3 are retained, while H3K4 methylation is completely erased. Furthermore, we experimentally demonstrated the functional roles of such retained modifications at early stages; H3K27ac at promoters is required for proper patterning of H3K4 and H3K27 methylation at zygotic genome activation (ZGA) and specific retention of H3K9me3 at telomeric regions maintains genomic stability during cleavage stage. These results expand the understanding of diversity and conservation of reprogramming in vertebrates and unveil previously uncharacterized functions of histone modifications retained during epigenetic reprogramming.