Epigenetic Control of Cell State By Chromatin Looping

Mammalian gene expression is regulated by various epigenetic mechanisms including DNA methylation, the histone code and the spatial organization of the genome. Knowledge of how patterns of gene expression are maintained or dynamically change during development is key to understanding control of cellular identity. Embryonic stem cells are a fascinating model system for studies of cellular identity since they can both self-renew and give rise to all cell types of an organism. The looping of chromatin by cohesin and CTCF is an important regulator of embryonic stem cell gene expression programs. Altered function of cohesin, and its regulators, disrupts proper gene expression programs and leads to differentiation. Changes in cohesin dynamics and localization are associated with aberrant organization of the genome within the nucleus. Cohesin-dependent chromatin loops serve as insulators of transcriptional activity and thereby link genome structure and genome function.