DAAM1 is a formin required for centrosome re-orientation during cell migration

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Disheveled-associated activator of morphogenesis 1 (DAAM1) is a formin downstream of Wnt signaling, essential for planar cell polarity.
• DAAM1 interacts with Disheveled (Dvl), functioning downstream of Frizzled receptors.
• Its precise localization and function in mammalian cells remain largely uncharacterized.

Purpose of the Study:

• To investigate the role of DAAM1 in mammalian cell migration and polarization.
• To elucidate the mechanisms by which DAAM1 influences cell polarity.
• To analyze the structure-function relationship of DAAM1 in cultured cells.

Main Methods:

• Utilized a specific antibody to detect DAAM1 localization via immunofluorescence.
• Performed knockdown experiments to assess the effects of DAAM1 depletion.
• Employed wound healing assays to study cell migration and Golgi reorientation.
• Generated stable cell lines expressing DAAM1 for further analysis.

Main Results:

• DAAM1 localizes to the acto-myosin system, co-localizing with ventral myosin IIB-containing actin stress fibers, particularly in the sub-nuclear region.
• An N-terminal region of DAAM1 mediates targeting to myosin IIB fibers, independent of F-actin or RhoA binding.
• DAAM1 depletion inhibits Golgi reorientation during wound healing, leading to unpolarized cell migration with multiple protrusions.
• Overexpression of DAAM1 enhances the myosin IIB stress fiber network, which opposes cell migration.

Conclusions:

• DAAM1 plays a critical role in cell polarity and migration by modulating the acto-myosin IIB system.
• The N-terminal half of DAAM1 is essential for its function.
• DAAM1 depletion severely impairs centrosomal re-polarization, indicating cooperation with the Cdc42 polarity complex.
• DAAM1's function in cultured cells mirrors its role in embryonic development.