Mechanical Stress Induced Crowding And Apoptosis Of Enamel Knot

The enamel knot is a signaling center during tooth development, and its maintenance and fate determination can affect the size and shape of the tooth germ. However, the heterogeneity, fate determination, and functional role of apoptosis in the enamel knot remain unknown. Using single-cell transcriptome analysis and immunostaining, we explored the heterogeneity and apoptosis of enamel knot. Using single-cell transcriptome analysis, we identified two groups of cells within the primary enamel knot: a core region with high Lef1 and low Sox9 expression, and a peripheral region with low Lef1 and high Sox9 expression. Cells in the core region have a high density and tend to undergo apoptosis, while cells in the peripheral region have a low density but can survive to form the buccal cusp. Further studies revealed that cells in the peripheral region undergo centripetal migration, accompanied by the activation of the stress response protein YAP1 and the upregulation of cytoskeletal remodeling genes. We conclude that the centripetal migration of Lef1 low cells in the peripheral enamel knot generates stress, inducing apoptosis in the core region and thereby affecting tooth crown morphology.