Translating cell polarity into tissue elongation

Abstract

Planar cell polarity, the orientation of single-cell asymmetries within the plane of a multicellular tissue, is essential to generating the shape and dimensions of organs and organisms. Planar polarity systems align cell behavior with the body axes and orient the cellular processes that lead to tissue elongation. Using Drosophila as a model system, significant progress has been made toward understanding how planar polarity is generated by biochemical and mechanical signals. Recent studies using time-lapse imaging reveal that cells engage in a number of active behaviors whose orientation and dynamics translate planar cell polarity into tissue elongation. Here we review recent progress in understanding the cellular mechanisms that link planar polarity to large-scale changes in tissue structure.

Planar cell polarity in moving cells: think globally, act locally

“…A third pathway also operates in the embryonic ectoderm to regulate PCP during germband extension (Bertet et al, 2004;Blankenship et al, 2006;Vichas and Zallen, 2011). Here, and henceforth, we consider exclusively the core PCP pathway, as the role of the Fat/Ds pathway in directional cell movements is less well established.…”

Regulation of PCP by the Fat signaling pathway

“…The embryonic ectoderm undergoes tissue elongation and narrowing during germ band extension. Polarized junctional rearrangements direct this tissue reorganization and depend on planar polarity that is independent of the PCP signaling proteins described above (Zallen 2007;Bertet and Lecuit 2009;Vichas and Zallen 2011). Another planarpolarized cell behavior that does not rely on the PCP pathway is the elongation of the Drosophila egg chamber during oogenesis.…”

Tricellulin regulates junctional tension of epithelial cells at tricellular contacts via Cdc42

“…The signaling pathways of small G proteins, including Cdc42, Rho and their effectors, which regulate F-actin polymerization and myosin II activation, are involved in this process (Jaffe and Hall, 2005;Smutny et al, 2010;Yamada and Nelson, 2007). The combination of strong cell-cell adhesion and the tension of the underlying actomyosin bundles at the AJC controls the shape of the epithelial cell border, the morphogenesis of epithelial cellular sheets and the remodeling of epithelial cells during development (Lecuit and Lenne, 2007;Lecuit et al, 2011;Vichas and Zallen, 2011).…”