报告题目：Dynamic chromatin reprogramming in mammalian early development
In mammals, extensive chromatin reorganization is essential for reprogramming terminally committed gametes to a totipotent state during preimplantation development. However, the global chromatin landscape and its dynamics in this critical period remain poorly understood. Recently, we conducted a genome-wide investigation of accessible chromatin in mouse preimplantation embryos using an improved ATAC-seq approach with CRISPR/Cas9-assisted mitochondrial DNA depletion. We show that despite extensive parental asymmetry in DNA methylome, the chromatin accessibility between the parental genomes is globally comparable after major zygotic genome activation. Accessible chromatin in early embryos is strongly shaped by transposable elements and overlaps extensively with promoters, putative enhancers, and, unexpectedly, transcription end sites of active genes. By integrating the maps of putative cis-regulatory elements and single-cell transcriptomes, we constructed the regulatory network of early development which helps to identify the key modulators for lineage specification. Finally, we found chromatin prior to genome activation shows a unique state that is featured by promiscuous transcription associated with repeats and unusually large open chromatin (up to over 100kb). These data indicate rather highly permissive chromatin before genome activation. Our data reveal a unique spatiotemporal chromatin configuration that accompanies early mammalian development.