Force measurements of Myosin II waves at the yolk surface during Drosophila dorsal closure.

The mechanical properties and the forces involved during tissue morphogenesis have been the focus of much research in the last years. Absolute values of forces during tissue closure events have not yet been measured. This is also true for a common force-producing mechanism involving Myosin II waves that results in pulsed cell surface contractions.

Magnetic tweezers optimized to exert high forces over extended distances from the magnet in multicellular systems.

Magnetic tweezers are mainly divided into two classes depending on the ability of applying torque or forces to the magnetic probe. We focused on the second category and designed a device composed by a single electromagnet equipped with a core having a special asymmetric profile to exert forces as large as 230 pN-2.8 μm Dynabeads at distances in excess of 100 μm from the magnetic tip.

Amnioserosa cell constriction but not epidermal actin cable tension autonomously drives dorsal closure.

Tissue morphogenesis requires coordination of multiple force-producing components. During dorsal closure in fly embryogenesis, an epidermis opening closes. A tensioned epidermal actin/MyosinII cable, which surrounds the opening, produces a force that is thought to combine with another MyosinII force mediating apical constriction of the amnioserosa cells that fill the opening.

SnapShot: Mechanical Forces in Development II.

The forces shaping an organism are not exclusively produced by actin/myosin II networks. In part II of this SnapShot, we present various alternative mechanisms. In addition to driving morphogenesis, cells use mechanical forces to sense and react to the specific mechanical properties of their environment.

SnapShot: Mechanical Forces in Development I.

Cell-type-specific F-actin structures and myosin motors are key generators of the forces that drive tissue morphogenesis in developing organisms. These cytoskeletal elements mediate defined cell deformation and control the arrangement of cell-cell contacts. This SnapShot presents a selection of morphogenetic processes, the analysis of which has pioneered specific types of F-actin/myosin-mediated force generation in development.