Crosstalk between basal extracellular matrix adhesion and building of apical architecture during morphogenesis

Shroom3 facilitates optic fissure closure via tissue alignment and reestablishment of apical-basal polarity during epithelial fusion

Optic cup morphogenesis is a complex process involving cellular behaviors such as epithelial folding, cell shape changes, proliferation, and tissue fusion. Disruptions to these processes can lead to an ocular coloboma, a congenital defect where the optic fissure fails to close. This study investigates the role of Shroom3, a protein implicated in epithelial morphogenesis, in mouse embryos during optic cup development. It was observed that Shroom3 is apically localized in the neural retina and retinal pigmented epithelium, and its deficiency leads to a both a conventional coloboma phenotype characterized by a gap in pigmented tissue as well as a unique type of coloboma where an ectopic ventral fold of neural tissue is present. Increased apical areas of both neural retina and retinal pigmented epithelial cells are present in the absence of Shroom3 leading to a greater apical surface area and disruption of optic fissure alignment. Neural retina specific gene ablation revealed that Shroom3 function in the RPE is likely sufficient to facilitate tissue alignment and permit fusion. However, the fusion process is ultimately disturbed due to a failure of the neural tissue to reestablish apical-basal polarity. Furthermore, it is demonstrated that Shroom3 deficiency also affects other epithelial fusion events in the embryo that rely on polarity reestablishment, such as lens vesicle separation, eyelid formation, and secondary palate closure. These findings highlight the importance of Shroom3 during optic cup morphogenesis, aid our understanding of optic fissure closure and coloboma formation, and implicates a role for Shroom3 in regulating apical-basal polarity.

Biomimetic tubular materials: from native tissues to a unifying view of new vascular, tracheal, gastrointestinal, oesophageal, and urinary grafts

Repairing tubular tissues-the trachea, the esophagus, urinary and gastrointestinal tracts, and the circulatory system-from trauma or severe pathologies that require resection, calls for new, more effective graft materials. Currently, the relatively narrow family of materials available for these applications relies on synthetic polymers that fail to reproduce the biological and physical cues found in native tissues. Mimicking the structure and the composition of native tubular tissues to elaborate functional grafts is expected to outperform the materials currently in use, but remains one of the most challenging goals in the field of biomaterials. Despite their apparent diversity, tubular tissues share extensive compositional and structural features. Here, we assess the current state of the art through a dual layer model, reducing each tissue to an inner epithelial layer and an outer muscular layer. Based on this model, we examine the current strategies developed to mimic each layer and we underline how each fabrication method stands in providing a biomimetic material for future clinical translation. The analysis provided here, addressed to materials chemists, biomaterials engineers and clinical staff alike, sets new guidelines to foster the elaboration of new biomimetic materials for effective tubular tissue repair.

Recoil Measurements in Drosophila Embryos: from Mounting to Image Analysis

Tension and force propagation play a central role in tissue morphogenesis, as they enable sub- and supra-cellular shape changes required for the generation of new structures. Force is often generated by the cytoskeleton, which forms complex meshworks that reach cell-cell or cell-extracellular matrix junctions to induce cellular rearrangements. These mechanical properties can be measured through laser microdissection, which concentrates energy in the tissue of interest, disrupting its cytoskeleton. If the tissue is undergoing tension, this cut will induce a recoil in the surrounding regions of the cut. This protocol describes how one can perform laser microdissection experiments and subsequently measure the recoil speed of the sample of interest. While we explain how to carry out these experiments in Drosophila embryos, the recoil calibration and downstream analyses can be applied to other types of preparations. Key features Allows measuring tension in live Drosophila embryos with a relatively simple approach. Describes a quick way to mount a high number of embryos. Includes a segmentation-free recoil quantification that reduces bias and speeds up analysis. Graphical overview.

Deciphering the interplay between autophagy and polarity in epithelial tubulogenesis

The Metazoan complexity arises from a primary building block, the epithelium, which comprises a layer of polarized cells that divide the organism into compartments. Most of these body compartments are organs formed by epithelial tubes that enclose an internal hollow space or lumen. Over the last decades, multiple studies have unmasked the paramount events required to form this lumen de novo. In epithelial cells, these events mainly involve recognizing external clues, establishing and maintaining apicobasal polarity, endo-lysosomal trafficking, and expanding the created lumen. Although canonical autophagy has been classically considered a catabolic process needed for cell survival, multiple studies have also emphasized its crucial role in epithelial polarity, morphogenesis and cellular homeostasis. Furthermore, non-canonical autophagy pathways have been recently discovered as atypical secretory routes. Both canonical and non-canonical pathways play essential roles in epithelial polarity and lumen formation. This review addresses how the molecular machinery for epithelial polarity and autophagy interplay in different processes and how autophagy functions influence lumenogenesis, emphasizing its role in the lumen formation key events.

The basement membrane controls size and integrity of the Drosophila tracheal tubes

Biological tubes are fundamental units of most metazoan organs. Their defective morphogenesis can cause malformations and pathologies. An integral component of biological tubes is the extracellular matrix, present apically (aECM) and basally (BM). Studies using the Drosophila tracheal system established an essential function for the aECM in tubulogenesis. Here, we demonstrate that the BM also plays a critical role in this process. We find that BM components are deposited in a spatial-temporal manner in the trachea. We show that laminins, core BM components, control size and shape of tracheal tubes and their topology within the embryo. At a cellular level, laminins control cell shape changes and distribution of the cortical cytoskeleton component α-spectrin. Finally, we report that the BM and aECM act independently-yet cooperatively-to control tube elongation and together to guarantee tissue integrity. Our results unravel key roles for the BM in shaping, positioning, and maintaining biological tubes.