The adipose tissue has an apical-basal polarity required for Col IV-dependent cell-cell adhesion

In epithelia, the apical-basal polarity machinery positions E-cadherin-based adherens junctions at the apical-lateral border to mediate cell-cell adhesion. The Drosophila adipose tissue, the fat body, forms a monolayer in which integrin-binding to collagen IV intercellular concentrations mediates cell-cell adhesion. How these atypical adhesion complexes form is unknown. Here we show that the fat body has apical-basal polarity, with aPKC, Crumbs, and Par-6 on the opposite side of Lgl and Dlg. Collagen IV, Laminin, Perlecan, and Nidogen are abundant in the basal basement membrane, while collagen IV predominates in the apical basement membrane. Crumbs, aPKC, Scribble, and Lgl knockdown in the fat body lead to cell-cell adhesion defects. Moreover, aPKC is essential for the formation of collagen IV intercellular concentrations. We further show that during fat body remodeling, Ecdysone regulates the loss of apical-basal polarity and collagen IV intercellular concentrations to induce cell-cell dissociation and swimming migration. Our work hence uncovers a novel role for apical-basal polarity in the Drosophila adipose tissue in regulating cell-cell adhesion via collagen IV intercellular concentrations.