Phenotype is a manifestation of a complicated relationship between the gene sequence that dictates the “what” of gene expression and regulatory elements that supply the crucial “when, where, and how.” The central components of gene regulation are transcription factors (TFs) – proteins that regulate transcription by binding to DNA regions adjacent to the gene. While TFs recognize specific DNA sequences, we do not fully understand the rules that allow regulators to distinguish among the millions of potentially bind-able sequences in the genome to select the tens of thousands chosen to be bound in vivo. Uncovering these rules is a key step in understanding the developmental and evolutionary processes that shape the observed phenotypic variation. Based on previous experiments we know that, despite the assumption that conserved function will correlate with conservation of TF binding, most TF binding events are species-specific (i.e. not evolutionarily conserved) and are driven by the underlying genetic sequence, not inter-species differences in nuclear environment. In this project, I will experimentally dissect the long-range sequence patterns that govern transcription factor binding. Aim 1: Scan TF binding in closely related species. I will use liver hepatocytes from closely related mouse strains to map the TF binding sites using chromatin immunoprecipitation (ChIP) combined with ultra highthroughput DNA sequencing (ChIP-seq). Aim 2: Identify species-specific TF binding events that do not follow simple binding rules. Find the long-range sequence changes associated with these events. Aim 3: Confirm our findings in related species and formulate rules underlying TF binding. A Marie-Curie International Reintegration Grant would enable this cutting-edge research and help me apply the molecular biology and population genetics skills I obtained during my PhD and postdoc in the United States in an excellent laboratory in the European Union.