Discovering enhancers by mapping chromatin features in primary tissue

Enhancers work with promoters to refine the timing, location, and level of gene expression. As they perform these functions, active enhancers generate a chromatin environment that is distinct from other areas of the genome. Therefore, profiling enhancer-associated chromatin features can produce genome-wide maps of potential regulatory elements. This review focuses on current technologies used to produce maps of potential tissue-specific enhancers by profiling chromatin from primary tissue. First, cells are separated from whole organisms either by affinity purification, automated cell sorting, or microdissection. Isolating the tissue prior to analysis ensures that the molecular signature of active enhancers will not become lost in an averaged signal from unrelated cell types. After cell isolation, the molecular feature that is profiled will depend on the abundance and quality of the harvested material. The combination of tissue isolation plus genome-wide chromatin profiling has successfully identified enhancers in several pioneering studies. In the future, the regulatory apparatus of healthy and diseased tissues will be explored in this manner, as researchers use the combined techniques to gain insight into how active enhancers may influence disease progression.