Cytoskeletal players in single-cell branching morphogenesis

The Endothelial Centrosome: Specific Features and Functional Significance for Endothelial Cell Activity and Barrier Maintenance

This review summarizes information about the specific features that are characteristic of the centrosome and its relationship with the cell function of highly specialized cells, such as endotheliocytes. It is based on data from other researchers and our own long-term experience. The participation of the centrosome in the functional activity of these cells, including its involvement in the performance of the main barrier function of the endothelium, is discussed. According to modern concepts, the centrosome is a multifunctional complex and an integral element of a living cell; the functions of which are not limited only to the ability to polymerize microtubules. The location of the centrosome near the center of the interphase cell, the concentration of various regulatory proteins in it, the organization of the centrosome radial system of microtubules through which intracellular transport is carried out by motor proteins and the involvement of the centrosome in the process of the perception of the external signals and their transmission make this cellular structure a universal regulatory and distribution center, controlling the entire dynamic morphology of an animal cell. Drawing from modern data on the tissue-specific features of the centrosome's structure, we discuss the direct involvement of the centrosome in the performance of functions by specialized cells.

Shaping subcellular tubes through vesicle trafficking: Common and distinct pathways

Cells with subcellular lumens form some of the most miniature tubes in the tubular organs of animals. These are often crucial components of the system, executing functions at remote body locations. Unlike tubes formed by intercellular or autocellular junctions, the cells with junctionless subcellular lumens face unique challenges in modifying the cell shape and plasma membrane organization to incorporate a membrane-bound tube within, often associated with dramatic cellular growth and extensions. Results in the recent years have shown that membrane dynamics, including both the primary delivery and recycling, is crucial in providing the cell with the flexibility to face these challenges. A significant portion of this information has come from two in vivo invertebrate models; the Drosophila tracheal terminal cells and the C. elegans excretory cell. This review focuses on the data obtained from these systems in the recent past about how trafficking pathways influence subcellular tube and branching morphogenesis. Given that such tubes occur in vertebrate vasculature, these insights are relevant to human health, and we contrast our conclusions with the less understood subcellular tubes of angiogenesis.

Contractile and expansive actin networks in Drosophila: Developmental cell biology controlled by network polarization and higher-order interactions

Actin networks are central to shaping and moving cells during animal development. Various spatial cues activate conserved signal transduction pathways to polarize actin network assembly at sub-cellular locations and to elicit specific physical changes. Actomyosin networks contract and Arp2/3 networks expand, and to affect whole cells and tissues they do so within higher-order systems. At the scale of tissues, actomyosin networks of epithelial cells can be coupled via adherens junctions to form supracellular networks. Arp2/3 networks typically integrate with distinct actin assemblies, forming expansive composites which act in conjunction with contractile actomyosin networks for whole-cell effects. This review explores these concepts using examples from Drosophila development. First, we discuss the polarized assembly of supracellular actomyosin cables which constrict and reshape epithelial tissues during embryonic wound healing, germ band extension, and mesoderm invagination, but which also form physical borders between tissue compartments at parasegment boundaries and during dorsal closure. Second, we review how locally induced Arp2/3 networks act in opposition to actomyosin structures during myoblast cell-cell fusion and cortical compartmentalization of the syncytial embryo, and how Arp2/3 and actomyosin networks also cooperate for the single cell migration of hemocytes and the collective migration of border cells. Overall, these examples show how the polarized deployment and higher-order interactions of actin networks organize developmental cell biology.

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

Tissues build complex structures like lumens and microvilli to carry out their functions. Most of the mechanisms used to build these structures rely on cells remodelling their apical plasma membranes, which ultimately constitute the specialised compartments. In addition to apical remodelling, these shape changes also depend on the proper attachment of the basal plasma membrane to the extracellular matrix (ECM). The ECM provides cues to establish apicobasal polarity, and it also transduces forces that allow apical remodelling. However, physical crosstalk mechanisms between basal ECM attachment and the apical plasma membrane remain understudied, and the ones described so far are very diverse, which highlights the importance of identifying the general principles. Here, we review apicobasal crosstalk of two well-established models of membrane remodelling taking place during Drosophila melanogaster embryogenesis: amnioserosa cell shape oscillations during dorsal closure and subcellular tube formation in tracheal cells. We discuss how anchoring to the basal ECM affects apical architecture and the mechanisms that mediate these interactions. We analyse this knowledge under the scope of other morphogenetic processes and discuss what aspects of apicobasal crosstalk may represent widespread phenomena and which ones are used to build subsets of specialised compartments.