NMII Forms a Contractile Transcellular Sarcomeric Network to Regulate Apical Cell Junctions and Tissue Geometry

Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
Current biology: CB (Impact Factor: 9.92). 04/2013; 23(8). DOI: 10.1016/j.cub.2013.03.039
Source: PubMed

ABSTRACT Nonmuscle myosin II (NMII) is thought to be the master integrator of force within epithelial apical junctions, mediating epithelial tissue morphogenesis and tensional homeostasis [1-3]. Mutations in NMII are associated with a number of diseases due to failures in cell-cell adhesion [4-8]. However, the organization and the precise mechanism by which NMII generates and responds to tension along the intercellular junctional line are still not known. We discovered that periodic assemblies of bipolar NMII filaments interlace with perijunctional actin and α-actinin to form a continuous belt of muscle-like sarcomeric units (∼400-600 nm) around each epithelial cell. Remarkably, the sarcomeres of adjacent cells are precisely paired across the junctional line, forming an integrated, transcellular contractile network. The contraction/relaxation of paired sarcomeres concomitantly impacts changes in apical cell shape and tissue geometry. We show differential distribution of NMII isoforms across heterotypic junctions and evidence for compensation between isoforms. Our results provide a model for how NMII force generation is effected along the junctional perimeter of each cell and communicated across neighboring cells in the epithelial organization. The sarcomeric network also provides a well-defined target to investigate the multiple roles of NMII in junctional homeostasis as well as in development and disease.

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Available from: Seham Ebrahim, Jan 29, 2015
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    • "Earlier confocal analyses showed that both NMIIA and NMIIB concentrate at the ZA in confluent MCF-7 monolayers and contribute to its morphological integrity (McLachlan and Yap, 2011; Smutny et al., 2011). Now, by applying higher resolution imaging with Structured Illumination Microscopy (SIM) we further find that both paralogs localize in puncta overlying the apical actin rings (Figure 1A), which may correspond to the sarcomeric-like organization of actomyosin seen at epithelial junctions in tissues (Ebrahim et al., 2013). "
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