This book is based on the NATO Advanced Research Workshop on "Mesenchymal-Epithelial Interactions in Neural Development" which was held in Berlin during March 1986. The idea that it may be the time for this workshop arose from a discussion among the organizers who met at a conference in Innsbruck. During the twenties, Spemann demonstrated that, in vertebrates, the formation of neuroepithelium depends on the induction by specific mesodermal derivatives. This was about the first time that mesenchymal-epithelial interactions had been recognized as an important mechanism in the development of an epithelial organ. Since then two things had become clear: 1) The identity and role of molecules, elaborated at mesenchymal-neuroepithelial interfaces had been partially elucidated in spinal cord and peripheral nerve ontogeny but, until recently, had been ignored in studies on the development of the brain. 2) In many-non-neural epithelia, the surrounding mesenchyme regulates such fundamental developmental steps as, for example, cell proliferation, morphogenesis and cell differentia tion, and there is no reason to exclude similar influences and interactions from brain development. It seemed to us that the importance and implications of many of these findings had not been appreciated by many developmental neurobiologists and that an attempt should be made to initiate discussions and exchange of ideas among different groups of scientists involved in extracellular matrix (ECM) research. This turned out to be a formidable task because of the great diversity of disciplines contributing findings to this active field.

The human body contains many specialized tissues that are capable of fulfilling an incredible variety of functions necessary for our survival. This volume in the Human Cell Culture Series focuses on mesenchymal tissues and cells. The in vitro study of mesenchymal cells is perhaps the oldest form of human cell culture, beginning with the culturing of fibroblasts. Fibroblasts have long been generically described in the literature, arising from many tissue types upon in vitro cell culture. However, recent studies, many enabled by new molecular biology techniques, have shown considerable diversity in fibroblast type and function, as described within this volume. Mesenchymal tissue types that are described within include bone, cartilage, tendons and ligaments, muscle, adipose tissue, and skin (dermis). The proper function of these tissues is predominantly dependent upon the proper proliferation, differentiation, and function of the mesenchymal cells which make up the tissue. Recent advancements in primary human mesenchymal cell culture have led to remarkable progress in the study of these tissues. Landmark experiments have now demonstrated a stem cell basis for many of these tissues, and, furthermore, significant plasticity and inter-conversion of stem cells between these tissues, resulting in a great deal of contemporary excitement and controversy. Newly-developed mesenchymal cell culture techniques have even lead to novel clinical practices for the treatment of disease.

gar discusses recent studies of the SF gene promoter that may be relevant to understanding the detailed molecular mechanism(s) by which soluble factors regulate SF production. Polverini and Nickoloff discuss another mechanism by which SF may enhance tumor growth, ie., stimulation of angiogenesis, the formation of new blood vessels from pre-existing microvessels. Angiogenesis is required for continued growth of most solid tumors, and provides a mechanism by which the stroma may continue to grow along with the tumor cells. Although endothelial cells are stromal cells, they express a number of epithelial characteristics including (i) epithelial-like tight junctions and junctional proteins; (ii) the ability to organize into flat­ tened tubular structures; (iii) the c-met receptor protein; and (iv) biologic responsiveness to SF. It is, perhaps, not surprising that vascular endothe­ lial cells may both produce and respond to SF in different situations. 'Epithelialness' may be defined in two ways: (i) expression of generic epithelial structures and proteins (eg., specialized junctions, junctional proteins [eg., cadherins, ZOl], cytokeratins); and (ii) production of specific differentiated products (eg., milk proteins by mammary epithelia, renin by renal tubular epithelia of the juxtaglomerular apparatus). Recent studies suggest that SF Ic-met signalling may mediate epithelia­ mesenchyme interconversion, in part by modifying some of the generic epithelial characteristics. Nusrat discusses the effects of SF on the epithelial junctional apparatus. Relatively little is known about whether and how SF regulates cell-specific differentiation.

This 1999 edition of The Neural Crest contains comprehensive information about the neural crest, a structure unique to the vertebrate embryo, which has only a transient existence in early embryonic life. The ontogeny of the neural crest embodies the most important issues in developmental biology, as the neural crest is considered to have played a crucial role in evolution of the vertebrate phylum. Data that analyse neural crest ontogeny in murine and zebrafish embryos have been included in this revision. This revised edition also takes advantage of recent advances in our understanding of markers of neural crest cell subpopulations, and a full chapter is now devoted to cell lineage analysis. The major research breakthrough since the first edition has been the introduction of molecular biology to neural crest research, enabling an elucidation of many molecular mechanisms of neural crest development. This book is essential reading for students and researchers in developmental biology, cell biology, and neuroscience.

Craniofacial development is a multistep and intricate process initially involving a number of inductive interactions that control neural and neural crest development, which are followed by a series of epithelial-mesenchymal interactions that control outgrowth, patterning, and skeletal differentiation. Certain aspects of craniofacial development are unique developmental processes in higher vertebrates. First, in higher vertebrates the cranial neural crest, in contrast to the trunk neural crest, gives rise to the skeletal structures. These skeletal elements include those comprising mem brane bone and secondary cartilage, which with the exception of the clavicle are tissue types found exclusively in the head in higher vertebrates. Second, with the exception of the tongue, the origin of the musculature is distinct from other regions of the body. The body and tongue muscles are formed from the segmented epithelial somites whilst the head musculature is formed from unsegmented paraxial and prechordal mesoderm. Furthermore, the signalling cascades that control myogenic differentia tion appear to be distinct as determined by gene expression and the response of myogenic cells to growth factors. Finally, the neurogenic placodes, which give rise to the sensory organs and some cranial ganglia, are only found in the head. Over recent years, there have been significant advances in our knowledge of the molecular proc esses that control craniofacial development in a number of animal models. This has given insight into the genes that control many aspects of head development from the initial induction of the head to the final stages of differentiation.

Epithelial phenotype is a dynamic stage of differentiation that can be modulated during several physiological or pathological events. The rapid conversion to a mesenchymal-like phenotype is called an epithelial-mesenchymal transition (EMT). The Rise and Fall of Epithelial Phenotype is the first book to comprehensively introduce the concept of EMT. The first part of this volume describes main examples and models and explains their physiological relevance. These examples include hydra morphogenesis, gastrulation in mouse, drosophila and sea urchin, as well as neural crest cell migration and heart morphogenesis in vertebrates. Part two reviews in detail, specific EMT molecular pathways covering extracellular induction, transduction and transcription response and modulation of cell-cell adhesion structures. It emphasizes new specific pathways with potential medical applications. EMTs can also be linked to pathological events such as wound healing and cancer progression, as detailed in this section of the book.

A discussion of the neural crest and neural crest cells, dealing with their discovery, their embryological and evolutionary origins, their cellular derivatives - in both agnathan and jawed vertebrates or gnathostomes - and the broad topics of migration and differentiation in normal development. The book also considers what goes wrong when development is misdirected by mutations, or by exposure of embryos to exogenous agents such as drugs, alcohol, or excess vitamin A, and includes discussions of tumours and syndromes and birth defects involving neural crest cells.