Maturation of focal adhesions through Dia1 during tissue shape changes. (A) Model for focal adhesion maturation during the onset of MDCK branching morphogenesis. Cells generate actin-rich protrusions from their basal surface into the collagen matrix. Protrusions are initially weakly adhered to collagen fibrils through nascent focal adhesions. Localized actin polymerization through Dia1 and myosin recruitment promote stabilization and maturation of focal adhesions. Mature adhesions resist turnover and allow cells to exert contractile forces against collagen fibrils to enable branching morphogenesis. (B) Dia1 as a mechanism by which tissues can regulate noninvasive and invasive motility. In the absence of Dia1 activity, cells can adhere sufficiently to the collagen matrix to mediate planar motility within the acinus and acinar rotation. Invasive motility into the collagen matrix requires that cells form mature adhesions dependent on Dia1.