aPKC regulates apical constriction to prevent tissue rupture in the Drosophila follicular epithelium

Apical-basal polarity is an essential epithelial trait controlled by the evolutionarily conserved PAR-aPKC po-larity network. Dysregulation of polarity proteins disrupts tissue organization during development and in dis-ease, but the underlying mechanisms are unclear due to the broad implications of polarity loss. Here, we un-cover how Drosophila aPKC maintains epithelial architecture by directly observing tissue disorganization after fast optogenetic inactivation in living adult flies and ovaries cultured ex vivo. We show that fast aPKC perturbation in the proliferative follicular epithelium produces large epithelial gaps that result from increased apical constriction, rather than loss of apical-basal polarity. Accordingly, we can modulate the incidence of epithelial gaps by increasing and decreasing actomyosin-driven contractility. We traced the origin of these large epithelial gaps to tissue rupture next to dividing cells. Live imaging shows that aPKC perturbation in-duces apical constriction in non-mitotic cells within minutes, producing pulling forces that ultimately detach dividing and neighboring cells. We further demonstrate that epithelial rupture requires a global increase of apical constriction, as it is prevented by the presence of non-constricting cells. Conversely, a global induction of apical tension through light-induced recruitment of RhoGEF2 to the apical side is sufficient to produce tis-sue rupture. Hence, our work reveals that the roles of aPKC in polarity and actomyosin regulation are sepa-rable and provides the first in vivo evidence that excessive tissue stress can break the epithelial barrier during proliferation.

Automated summary

Research reveals that aPKC protein in Drosophila plays a crucial role in maintaining epithelial structure, and its dysregulation leads to the formation of epithelial gaps, which are caused by increased epithelial constriction rather than the loss of apical-basal polarity. By manipulating constriction, the incidence of epithelial gaps can be modulated. The study also traces the origin of large epithelial gaps to tissue rupture next to dividing cells. Excessive tissue stress can break the epithelial barrier during proliferation.