Comparative Mechanisms of Branching Morphogenesis in Diverse Systems

Abstract

Much progress has been made in recent years toward understanding mechanisms controlling branching morphogenesis, a fundamental aspect of development in a variety of invertebrate and vertebrate organs. To gain a deeper understanding of how branching morphogenesis occurs in the mammary gland, we compare and contrast the cellular and molecular events underlying this process in both invertebrate and vertebrate organs. Thus, in this review, we focus on the common themes that have emerged from such comparative analyses and discuss how they are implemented via a battery of signaling pathways to ensure proper branching morphogenesis in diverse systems.

Tracheal branching morphogenesis inDrosophila: new insights into cell behaviour and organ architecture

“…It also remains to be investigated whether controlled cell rearrangement and cell intercalation, and whether the formation of apical matrices or the de novo formation of luminal space in distinct cell types, are intimately linked to certain stages of the branching process in the lung or ureteric bud. The same considerations apply to other organs that undergo excessive branching, such as the salivary gland or the mammary gland (Tucker, 2007;Lu et al, 2006;Cardoso and Lu, 2006).…”

“…An obvious question to ask at this point is whether similar cellular activities are involved in branching morphogenesis in other organisms (see also Lu et al, 2006). In the following section, we briefly discuss a few such similarities and differences.…”

“…The organ that is most often compared to the developing Drosophila tracheal system is the mammalian lung (Cardoso and Lu, 2006;Hogan and Kolodziej, 2002;Warburton et al, 2005). The finding that Fgf10 is expressed in a dynamic fashion at branch tips in the mammlian lung and is intimately linked to the branching process has highlighted that molecular similarities exist between branching in the mammalian lung and the insect trachea (Bellusci et al, 1997;Sekine et al, 1999;De Moerlooze et al, 2000).…”

“…It also remains to be investigated whether controlled cell rearrangement and cell intercalation, and whether the formation of apical matrices or the de novo formation of luminal space in distinct cell types, are intimately linked to certain stages of the branching process in the lung or ureteric bud. The same considerations apply to other organs that undergo excessive branching, such as the salivary gland or the mammary gland (Tucker, 2007;Lu et al, 2006; Cardoso and Lu, 2006).A rather astonishing number of similarities between the developing tracheal system and the formation of blood vessels via angiogenesis have recently emerged. The vertebrate vasculature is first assembled from scattered endothelial precursor cells, and is then enlarged and remodelled by the sprouting, splitting and regression of branches, which shape a hierarchical vascular network that allows directional blood flow (Carmeliet, 2003).…”

“…The process relies on directed cell migration, controlled cell rearrangement and cell intercalation, the secretion of apical matrices to help keep branch cells together and to help shape the luminal space, and the de novo formation of luminal space in distinct cell types. Several genes that play important roles in branching have been identified, and the molecular events that underlie these cellular activities are beginning to be worked out.An obvious question to ask at this point is whether similar cellular activities are involved in branching morphogenesis in other organisms (see also Lu et al, 2006). In the following section, we briefly discuss a few such similarities and differences.…”