FoxA factors: the chromatin key and doorstop essential for liver development and function.

Heslop, James A; Duncan, Stephen A

Pioneer factors are transcriptional regulators with the capacity to bind inactive regions of chromatin and induce changes in accessibility that underpin cell fate decisions. The FOXA family of transcription factors is well understood to have pioneer capacity. Indeed, researchers have uncovered numerous examples of FOXA-dependent epigenomic modulation in developmental and disease processes. Despite the presence of FOXA being essential for correct epigenetic patterning, the need for continued FOXA presence postchromatin modulation has been debated. In a recent study in this issue of Genes & Development, Reizel and colleagues (pp. 1039-1050) show that the tissue-specific ablation of FOXA1/2/3 in the adult mouse liver results in the collapse of the epigenetic profile that maintains the hepatic gene expression profile. Thus, FOXA functions as a key, opening regions of chromatin during development, and as a doorstep, maintaining the established euchromatic structure in adult tissue.