DNA regulatory element usage is driven largely by developmental stage, even within distinct cell lineages. Daniel J. McKay¹, Jason D. Lieb^1,2. 1) Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC; 2) Carolina Center for Genome Sciences.

   The defining feature of animal development is creation of a diversity of cell types and body parts from a single genome. Central to this process is differential regulation of gene expression. A prerequisite to understanding how genes are regulated differently in different cells is to identify all of the functional DNA elements in the genome. Recent advances in methods and technology have led to high-resolution maps of DNA regulatory elements across multiple stages of Drosophila development. However, these data were obtained from whole animals, and thus lack information on the cellular source of the signal. To determine how the genome is used in different cell lineages at different stages of development, we have generated genome-wide open chromatin and gene expression profiles from two distinct cell types and from two distinct axial positions at two stages of embryogenesis. While differences exist in the identity of DNA regulatory elements used in different cell types, we find that developmental stage has the greatest influence on which regions of the genome are utilized across all cells examined.