Polarity protein Par3/Bazooka follows myosin-dependent junction repositioning.

TitlePolarity protein Par3/Bazooka follows myosin-dependent junction repositioning.
Publication TypeJournal Article
Year of Publication2017
AuthorsWeng, M, Wieschaus, E
JournalDev Biol
Date Published2017 Feb 15
KeywordsActomyosin, Adherens Junctions, Animals, Down-Regulation, Drosophila melanogaster, Drosophila Proteins, Epithelial-Mesenchymal Transition, Epithelium, Female, Intracellular Signaling Peptides and Proteins, Male, Membrane Proteins, Mesoderm, Snail Family Transcription Factors

<p>The polarity protein Par3/Bazooka (Baz) has been established as a central component of the apical basal polarity system that determines the position of cell-cell junctions in epithelial cells. Consistent with that view, we show that shortly before gastrulation in Drosophila, Baz protein in the mesoderm is down-regulated from junctional sites in response to Snail (Sna) expression. This down-regulation leads to a specific decrease in adherens junctions without affecting other E-Cadherin pools. However, we further show that, interactions between Baz and junctions are not unidirectional. During apical constriction and the internalization of the mesoderm, down-regulation of Baz is transiently blocked as adherens junctions shift apically and are strengthened in response to tension generated by contractile actomyosin. When such junction remodeling is prevented by down-regulating myosin, Baz is lost prematurely in mesodermal epithelium. During such apical shifts, Baz is initially left behind as the junction shifts position, but then re-accumulates at the new location of the junctions. On the dorsal side of the embryo, a similar pattern of myosin activity appears to limit the basal shift in junctions normally driven by Baz that controls epithelium folding. Our results suggest a model where the sensitivity of Baz to Sna expression leads to the Sna-dependent junction disassembly required for a complete epithelium-mesenchymal transition. Meanwhile this loss of Baz-dependent junction maintenance is countered by the myosin-based mechanism which promotes an apical shift and strengthening of junctions accompanied by a transient re-positioning and maintenance of Baz proteins.</p>

Alternate JournalDev Biol
PubMed ID28063874
PubMed Central IDPMC5515594
Grant ListK99 HD088764 / HD / NICHD NIH HHS / United States
R37 HD015587 / HD / NICHD NIH HHS / United States