G Model
ARTICLE IN PRESS
YSCDB-1570; No. of Pages 1
Seminars in Cell & Developmental Biology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Seminars in Cell & Developmental Biology journal homepage: www.elsevier.com/locate/semcdb
Tubes lead the way
Tubular structures in all animals make up most of the essential organ systems, ranging from salivary glands or trachea in the fly to the vertebrate neural tube, the vascular system and mammary glands. All these different tissues form through processes collectively labelled tubulogenesis. Tubes can vary enormously in their architecture, from simple unbranched tubes to highly elaborated ductal trees, formed through a special type of tubulogenesis called branching morphogenesis. In a collection of reviews covering tubulogenesis examples from different model systems, such as Drosophila, zebrafish, mouse and in vitro culture, this issue aims to highlight common features that have emerged as being used in different types of tubulogenesis, but it also illustrates that specific organs have their own elaborate way of forming the type of tube that is crucial for a correct functioning of the tissue that is forming. Advances in live imaging as well as genetic tools have greatly aided the study of tubulogenesis over the last years. Invertebrate models still have an important role to play due to their great accessibility for imaging and ease of genetic manipulation, but vertebrate systems are catching up fast. In this issue, we start off with studies on Drosophila tubular systems. Girdler and Röper focus on cell shape changes and morphogenetic mechanisms that shape the embryonic salivary gland, whilst Caviglia and Luschnig as well as Weavers and Skaer discuss the roles of very specialised cells that direct tubulogenesis, the tip cells, in their respective tube models, the trachea and the fly renal tubules. We then switch to vertebrate models and the, in several aspects unique, mechanisms that shape the teleost neural tube as detailed by Buckley and Clarke. Also in zebrafish where live imaging allows beautiful analysis of morphogenesis, Schuermann, Helker & Herzog describe the mechanisms that shape and refine the zebrafish
vascular system. Continuing with analysis of the vascular system, but now using the mouse as a model, Neufel, Planas-Paz & Lammert describe mechanisms that drive the formation of both the blood as well as the lymphatic vascular system in mice. Both studies on vascular development again highlight the importance of tip cells in the regulation of placing forming tubes within the context of surrounding tissues and in elaborating and fusing tubular branches. Analysis of the pubertal elaboration of the ductal tree that forms the mammary gland in mice poses particular challenges to live and cellular analysis, as the process is slow and occurs in an optically near-inaccessible tissue environment. Huebner and Ewald discuss how the use of in vitro primary organoids in 3D culture has only recently allowed labs to image these processes live and has illuminated mechanisms that differ widely from other collective migratory processes. Elaborating further on the usefulness and accessibility of epithelial 3D in vitro culture, Zegers compares different 3D models to their in vivo counterparts, illustrating where in vitro culture has a strong role to play to complement in vivo analyses. Bringing all the current knowledge together, it appears that, even though at a cellular level we find some commonalities of mechanisms between different tubulogenesis systems, nonetheless many very elaborate and specialised mechanisms operate in different tissues and animal models. What appears to be conserved is the need to tie the epithelial polarity of the constituent cells to the mechanism of tube formation. Polarity needs to be maintained, modulated or newly generated, and especially basal cues given by the surrounding extracellular matrix or basal lamina, communicated into the cell interior by integrin receptors and related molecules, have emerged as key players in all systems discussed here. Available online xxx
http://dx.doi.org/10.1016/j.semcdb.2014.04.017 1084-9521/© 2014 Published by Elsevier Ltd.
Please cite this article in press as: Tubes lead the way. Semin Cell Dev Biol (2014), http://dx.doi.org/10.1016/j.semcdb.2014.04.017
ARTICLE IN PRESS
YSCDB-1570; No. of Pages 1
Seminars in Cell & Developmental Biology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Seminars in Cell & Developmental Biology journal homepage: www.elsevier.com/locate/semcdb
Tubes lead the way
Tubular structures in all animals make up most of the essential organ systems, ranging from salivary glands or trachea in the fly to the vertebrate neural tube, the vascular system and mammary glands. All these different tissues form through processes collectively labelled tubulogenesis. Tubes can vary enormously in their architecture, from simple unbranched tubes to highly elaborated ductal trees, formed through a special type of tubulogenesis called branching morphogenesis. In a collection of reviews covering tubulogenesis examples from different model systems, such as Drosophila, zebrafish, mouse and in vitro culture, this issue aims to highlight common features that have emerged as being used in different types of tubulogenesis, but it also illustrates that specific organs have their own elaborate way of forming the type of tube that is crucial for a correct functioning of the tissue that is forming. Advances in live imaging as well as genetic tools have greatly aided the study of tubulogenesis over the last years. Invertebrate models still have an important role to play due to their great accessibility for imaging and ease of genetic manipulation, but vertebrate systems are catching up fast. In this issue, we start off with studies on Drosophila tubular systems. Girdler and Röper focus on cell shape changes and morphogenetic mechanisms that shape the embryonic salivary gland, whilst Caviglia and Luschnig as well as Weavers and Skaer discuss the roles of very specialised cells that direct tubulogenesis, the tip cells, in their respective tube models, the trachea and the fly renal tubules. We then switch to vertebrate models and the, in several aspects unique, mechanisms that shape the teleost neural tube as detailed by Buckley and Clarke. Also in zebrafish where live imaging allows beautiful analysis of morphogenesis, Schuermann, Helker & Herzog describe the mechanisms that shape and refine the zebrafish
vascular system. Continuing with analysis of the vascular system, but now using the mouse as a model, Neufel, Planas-Paz & Lammert describe mechanisms that drive the formation of both the blood as well as the lymphatic vascular system in mice. Both studies on vascular development again highlight the importance of tip cells in the regulation of placing forming tubes within the context of surrounding tissues and in elaborating and fusing tubular branches. Analysis of the pubertal elaboration of the ductal tree that forms the mammary gland in mice poses particular challenges to live and cellular analysis, as the process is slow and occurs in an optically near-inaccessible tissue environment. Huebner and Ewald discuss how the use of in vitro primary organoids in 3D culture has only recently allowed labs to image these processes live and has illuminated mechanisms that differ widely from other collective migratory processes. Elaborating further on the usefulness and accessibility of epithelial 3D in vitro culture, Zegers compares different 3D models to their in vivo counterparts, illustrating where in vitro culture has a strong role to play to complement in vivo analyses. Bringing all the current knowledge together, it appears that, even though at a cellular level we find some commonalities of mechanisms between different tubulogenesis systems, nonetheless many very elaborate and specialised mechanisms operate in different tissues and animal models. What appears to be conserved is the need to tie the epithelial polarity of the constituent cells to the mechanism of tube formation. Polarity needs to be maintained, modulated or newly generated, and especially basal cues given by the surrounding extracellular matrix or basal lamina, communicated into the cell interior by integrin receptors and related molecules, have emerged as key players in all systems discussed here. Available online xxx
http://dx.doi.org/10.1016/j.semcdb.2014.04.017 1084-9521/© 2014 Published by Elsevier Ltd.
Please cite this article in press as: Tubes lead the way. Semin Cell Dev Biol (2014), http://dx.doi.org/10.1016/j.semcdb.2014.04.017
