Brg1 Governs a Positive Feedback Circuit in the Hair Follicle for Tissue Regeneration and Repair

In 2013, researchers discovered that Brg1, a chromatin-remodeling enzyme, is essential for hair follicle regeneration and repair. Brg1 regulates hair follicle stem cells by being activated by sonic hedgehog (Shh) signaling, which initiates hair regeneration. It then activates Shh in matrix cells to sustain hair growth, creating a positive feedback loop. Without Brg1, bulge cells are depleted, partly due to increased expression of the cell-cycle inhibitor p27Kip¹. Brg1 also aids in epidermal repair after skin injury. The study, which did not specify the number of mice used, showed that Brg1 is necessary for bulge cell proliferation and Shh expression. The findings highlight a molecular circuit involving Brg1, NF-kB, Gli proteins, and Shh signaling that is crucial for maintaining the stem cell reservoir and promoting tissue regeneration. The study also involved human bulge cell lines, with some experiments conducted in triplicates with N=6 samples each.