Extracellular matrix stiffness cues junctional remodeling for 3D tissue elongation

Abstract

Organs are sculpted by extracellular as well as cell-intrinsic forces, but how collective cell dynamics are orchestrated in response to environmental cues is poorly understood. Here we apply advanced image analysis to reveal extracellular matrix-responsive cell behaviors that drive elongation of the Drosophila follicle, a model system in which basement membrane stiffness instructs three-dimensional tissue morphogenesis. Through in toto morphometric analyses of wild type and round egg mutants, we find that neither changes in average cell shape nor oriented cell division are required for appropriate organ shape. Instead, a major element is the reorientation of elongated cells at the follicle anterior. Polarized reorientation is regulated by mechanical cues from the basement membrane, which are transduced by the Src tyrosine kinase to alter junctional E-cadherin trafficking. This mechanosensitive cellular behavior represents a conserved mechanism that can elongate edgeless tubular epithelia in a process distinct from those that elongate bounded, planar epithelia.

Oriented basement membrane fibrils provide a memory for F-actin planar polarization via the Dystrophin-Dystroglycan complex during tissue elongation

“…Between these phases, around stage 7-8, JAK-STAT and Fat2 seem to be integrated in a third mechanism based on a BM stiffness gradient . Interestingly, a very recent report suggests that this gradient may not directly influence tissue shape but rather do so by modifying the properties of the follicle cells underneath (Chen et al, 2019). Here, we show that the DAPC influences elongation mainly at very late stages, suggesting the existence of a fourth mechanistic elongation phase.…”

Distinct activities of Scrib module proteins organize epithelial polarity

“…UAS-myr-Scrib::V5 was generated by appending the N-terminal myristoylation signal from Src42A and C-terminal V5 tag to the Scrib A2 cDNA, and UASp-Scrib C4AC11A ::GFP was generated via site-directed mutagenesis. Acyl-Biotin Exchange was performed by modifying published protocols (39,68), using anterior L3 larval lysates; biotinylated protein was purified using magnetic beads and analyzed by western blot. Images were acquired using Zeiss LSM700 or LSM780 laser scanning confocal microscopes with LD C-Apochromat 40x/NA1.1 W or Plan Apochromat 63x/NA1.4 oil objectives.…”

“…FRAP experiments were performed as previously described (68). Briefly, follicles were dissected in media as above, supplemented with 2% human insulin (Sigma) and embedded in 0.5% low melting agarose in a glass bottom dish.…”

“…Intensities of the bleached region, reference region and background were manually measured using Fiji (69). Background and imagingdependent photobleaching were corrected as previously described (68). Recovery curves were fitted using Graphpad Prism as previously described (68).…”

“…Background and imagingdependent photobleaching were corrected as previously described (68). Recovery curves were fitted using Graphpad Prism as previously described (68).…”