Molecular Acrobats: How CHD Remodelers Shape the Genetic Playground to License Cell Identity.

In eukaryotes, DNA is not a naked repository of genetic information but is tightly wound around histone octamers to form nucleosomes. While this packaging solves the spatial problem of fitting 2 meters of DNA into a microscopic nucleus, it creates a massive accessibility problem for DNA-templated events, including transcription, replication, and DNA repair. Here, we review how the chromodomain helicase DNA-binding (CHD) family of ATP-dependent nucleosome remodelers act as the molecular acrobats of the chromatin accessibility landscape. We highlight that the three CHD subfamilies represent a developmental division of labor: subfamily I maintains pluripotent chromatin accessibility, subfamily II drives lineage commitment through chromatin closure, and subfamily III establishes tissue-specific enhancer and promoter accessibility during organogenesis. By dynamically transforming chromatin architecture through nucleosome sliding, spacing, and ejection, CHD remodelers license the transitions between cell states, ensuring that the epigenetic landscape is reshaped for the specific needs of a stem cell today and a differentiated cell type tomorrow. We discuss how disruption of this licensing, through mutation or loss of family members, leads to severe neurodevelopmental disorders, including CHARGE syndrome, autism spectrum disorder, and intellectual disability. We close by raising outstanding questions including how CHD activity is regulated, how co-expressed paralogs coordinate their activities, and whether CHD dysfunction can be therapeutically targeted.