For centuries, curious observers have been intrigued by the formation of ramified structures. The complexity and diversity in branching patterns among trees, alga, lung and the mammary gland, to name a few biological examples,have left the impression that it will be difficult to understand the basic principles that orchestrate branching morphogenesis. However, discoveries made in the past decade in biological systems, as well as in physical ones, such as rivers, oil fields, viscous fingers (elongated duct-like structures that form when one fluid penetrates into a more viscous one) and metallurgy, indicate that apparently disparate branching systems seem to share deep similarities in the forces and processes that shape branching. Moreover, branching morphogenesis in vertebrate organs occurs for the most part during embryonic development, when progenitor cells are extremely abundant. Therefore, the study of branching, which involves characterizing the interactions between epithelial, mesenchymal and endothelial cells during development, is relevant to understanding the interplay that occurs between niche cells and stem cells in adult tissues. In addition, understanding how cell shape remodeling and cell matrix interaction are coordinated during the process of branching may also reveal the changes that occur in adult tissues during the repair process after injury or during regeneration. Finally, the field has also more recently benefited from the input of physicists interested in proposing theoretical models based on the different kinds of forces at work during branching. Therefore, putting together a book dedicated to the branching process of different organs is timely indeed.FIG1
Branching Morphogenesis Edited by Jamie A. Davies
Springer (2005) 258 pages
ISBN 0-387-25615-6
$139 (hardback)
The techniques described in this book to study branching mophogenesis are relevant to biochemistry, molecular genetics, cell biology, anatomy,developmental biology, biophysics and computer modeling
Jamie Davies, the editor of Branching Morphogenesis, has recruited a comprehensive team of experts to cover many important aspects of this field. The targeted audience for this book is both developmental biologists and students. The book is divided into 13 chapters. Chapter 2 deals with branching morphogenesis in vertebrate neurons. Within the developing vertebrate nervous system, strict control of branching morphogenesis is essential to establish appropriate circuitry, as the geometry of neuronal arbors critically influences their functional properties. Chapter 3 focuses on the branching of single cells in Arabidopsis, whereas Chapter 4 covers branching in fungal hyphae and fungal tissues, in which the authors describe a sophisticated mathematical model that simulates fungal growth and branching. Chapter 5 discusses branching in colonial hydroids, which are the most-studied cnidarian group with respect to developmental biology. Chapter 6 describes how the tree-like vascular network is established, and Chapter 7 discusses the importance of extracellular matrix remodeling in mammary gland branching morphogenesis. Chapters 8 to 11 deal with branching in mammalian kidneys,salivary glands, prostate and uterine glands, whereas Chapter 12, which is written by a physicist, is dedicated to the physical mechanisms of branching morphogenesis.
Why cover branching morphogenesis in different organs and organisms?
Some branching systems, such as the tracheal placode in Drosophila, or the lung or kidney in vertebrates, are more studied than others, and the information presented in this book will allow the reader to have an integrated view of the control of the branching process across a broader spectrum of organisms and tissues. Aficionados of branching morphogenesis can therefore apply techniques developed by others to their system of interest, to gain valuable information in the weak areas of their own system with relative ease. In particular, the various specialized techniques described in this book to study the process of branching mophogenesis are relevant to the fields of biochemistry, molecular genetics,cell biology, anatomy, developmental biology, biophysics and computer modeling.
The morphogenetic code: still to be deciphered?
Chapter 12 presents Dr Fleury's view of branching morphogenesis. As an example, the fractal iterative model of the `lung' based on simple building principles is discussed. It is proposed that these building principles are re-iterated many times to give rise to ramified structures. Identifying these building principles is crucial if we want to break the branching morphogenetic code, which involves a master routine that sequentially or simultaneously controls various branching subroutines. A key subroutine controlling bud formation, for example, involves the modulation of cellular properties such as differential cell adhesion, cell motility, cell-matrix interactions and cytoskeletal organization. How this basic subroutine coordinates with another subroutine that controls cell proliferation and differentiation is still unclear. This book gives an integrated view of the many parameters controlling branching morphogenesis.
A view of how branching is regulated
The importance of paracrine factors, such as members of the bone morphogenetic protein (Bmp), fibroblast growth factor (Fgf), Wnt and Hedgehog(Hh) families, which are produced locally in the immediate vicinity of the branching structure and which can positively or negatively regulate branching,has been established in vivo and in vitro in many systems. Interestingly,Chapter 7 (which deals with mammary gland branching morphogenesis) and Chapter 10 (which deals with the branching of the prostate) also underscore the role of sex hormones, which are produced at other locations in the body and which control organ development in association with local signals. Chapter 8, on kidney branching, discusses the importance of paracrine signals and associated feedback loops in controlling the branching process in this organ. In Chapter 5, the authors show that autocrine signaling is important in the development of branched structures, such as in the fungi described in Chapter 4, and in the hydroids described in Chapter 5. And finally, the importance of the extracellular matrix for the branching of the mammary gland comes under the spotlight in Chapter 7.
In conclusion, this book on branching morphogenesis contains an excellent combination of articles that will allow the reader to rapidly gain an overview of the current knowledge and ideas in the field, and that will inspire them to take their research on this topic to the next level of functional analysis.
