Catalytic-Dependent and -Independent Activities of Polycomb Repressive Complex 1 Differentially Regulate Skin Stem Cell Specification

The document presents a study on the role of Polycomb repressive complex 1 (PRC1) in skin stem cell specification, revealing that PRC1's catalytic-dependent and -independent activities differentially regulate skin epithelial stem cell fate. The study found that murine skins with catalytically inactive PRC1 showed normal epidermal and hair development but had an expansion of Merkel cells. In contrast, PRC1-null skins exhibited a loss of epidermal integrity, impaired hair development, and a loss of Merkel cells. The research demonstrated that catalytic-dependent PRC1 activity is necessary for proper PRC2-mediated H3K27me3 deposition and the maintenance of the undifferentiated state of skin stem cells by repressing Merkel cell lineage genes. Conversely, PRC1's catalytic-independent activity is crucial for activating key lineage genes required for hair development and Merkel cell specification. The findings highlight the complex functions of PRC1 in controlling somatic stem cells through gene activation and repression mechanisms.