The Transcription Factor Binding Landscape of Mouse Development

Gene regulators physically associate to the genome, in a combinatorial fashion, to drive tissue-specific gene expression programs. Uncovering the genome-wide activity of all gene regulators across tissues is therefore needed to understand how the genome is regulated during development. Here, we take a first step forward towards achieving this goal. Using CUT&RUN, we systematically measured the genome-wide binding profiles of key transcription factors and cofactors that mediate the activity of ontogenetically relevant signaling pathways in select mouse tissues at two developmental stages. Computation of the numerous genome-wide binding datasets unveiled a large degree of tissue and time-specific activity for each gene regulator, and several factor-specific idiosyncrasies. Moreover, we identified "popular" regulatory regions that are bound by a multitude of pathway regulators. Popular regions tend to be more evolutionarily conserved, implying their essentiality. Consistently, they lie in the proximity of genes whose dysregulation causes early embryonic lethality in the mouse. Moreover, the human homologs of these regions are also bound by many gene regulators and are highly conserved in human populations, indicating that they retain functional relevance for human development. This work constitutes a decisive step towards understanding how the genome is simultaneously read and used by gene regulators in a holistic fashion and unveils multiple genomic mechanisms that drive embryonic development.