Polycomb chromatin topology enables long-range enhancer recruitment during craniofacial development

Little is known about how three-dimensional chromatin topology shapes mammalian craniofacial development. In mouse cranial neural crest cells, a Polycomb Repressive Complex 2 (PRC2)-dependent chromatin architecture is established before migration. This configuration maintains craniofacial gene promoters poised and connects them with distal Polycomb tethering elements, positioning promoters in spatial proximity to future long-range enhancers. Deletion of Ezh2 disrupts this early topology, causing inappropriate gene derepression in post-migratory craniofacial subpopulations where these genes are normally silenced, and failure of long-range enhancer recruitment where activation is required, thereby impairing proper gene expression. We further identify a distal Polycomb tethering element essential for Hoxa2 enhancer recruitment across topologically associating domains. Thus, Polycomb acts not only as a transcriptional repressor, but also as a chromatin-folding organizer that prepares developmental genes for later activation, by facilitating subsequent recruitment of distal active enhancers previously not in contact. Polycomb-mediated topology therefore orchestrates the transition from progenitor plasticity to precise spatiotemporal control of morphogenetic gene programs during neural crest development and face formation. This study shows how Polycomb shapes 3D chromatin in early cranial crest cells, preparing craniofacial genes for later activation by enabling recruitment of distant regulatory elements to ensure proper facial development.