This figure introduces the basic mechanism of WNT pathway. When the WNT pathway is opened, three proteins on the cell membrane bind, inhibiting the activity of corresponding kinases, reducing the phosphorylation of β-catenin. And β-catenin aggregates in the nucleus, BMP4 is its downstream pathway. In the formation and differentiation of lung, β-catenin plays an active role in BMP4, and then activates exogenous mesenchymal stem cells to differentiate into epithelial cells, regulating lung injury and repair. In corneal stratification, β-catenin inhibits BMP4