Cell, Vol. 93, 457-459,
November
2, 1990, Copyright
0 1990 by Cell Press
Book Review
Fingerprints, the Wall of Death, and Other Tales Morphogenesis: The Cellular and Molecular Processes of Developmental Anatomy. By J. Bard. Cambridge: Cambridge University Press. (1990). 303 pp. $54.50. For many biologists, understanding development has become synonymous with analyzing how tissue-specific gene expression is effected, often using a tissue culture model. While this approach is clearly valuable, the remarkable patterning of that tissue in the whole organism is often forgotten. How, for example, does a neural crest cell find its way between the mounds of somites and neural tube, and in fact, why does it begin to migrate at all? How do collagen fibrils become aligned in a perfectly parallel two-dimensional array between muscle and bone to form a tendon? Jonathan Bard has chosen to write about such “difficult” questions-asking how a tissue gets its shape, how cells “know” where to move, and whether one can find a common “language” to describe multicellular organizations as diverse as the division of a gland into ducts and the formation of the cornea. I enjoyed this book a great deal, if only to be reminded that embryogenesis is richly multilayered and intricate. It is a fact-filled book, but by no means a comprehensive reference manual. Although it is organized quite coherently and does synthesize the information presented into a useful conclusion, it is clearly a personal voyage into morphogenesis. Many interesting examples are documented and peppered with opinion, and really, one of the nicest aspects of this book is its subjectivity, which challenges the reader and makes for highly interactive reading. The book can be divided into four main sections. Several initial chapters introduce the kinds of question Bard is interested in and the aims of the book. One of these puts a temporal perspective on the subject by describing the history of morphogenesis, and the dogma of the 19th century (perpetrated primarily by Ernst Haeckel) that kept developmental analysis from progressing. It was largely Wilhelm Roux (“remembered for two wrong deductions and a journal” [p. 111) who revitalized the study of “developmental mechanics:’ A later chapter outlines a few fascinating examples of morphogenesis-including development of the seemingly simple cornea, whose final structure in the chicken requires 19 separable steps, occurring over 17 days of gestation! Bard then moves on to describe (briefly) what seems to be known about the molecular basis of morphogenesis: the components of the extracellular matrix, cell surface adhesion molecules, and cytoskeletal elements; and how each of these may contribute to tissue organization. For example, one role of the extracellular matrix is to generate
space into which cells can migrate. During cornea1 morphogenesis, a matrix of hyaluronic acid and proteoglycans is secreted between the lens and cornea1 rudiments. This absorbs water, swells, and allows the ingress of neural crest cells that will form the cornea1 endothelium. An infrequently considered function of cell surface adhesion molecules is to control cell movement. For example, do neural crest cells migrate because they are intrinsically more motile than, say, epidermal cells? Probably not; rather, the attachments that neural crest cells make to their environment are tenuous-apparently mediated only by neural cell adhesion molecule, which disappears during migration and resurfaces (so to speak) at its cessation. Two subsequent chapters deal with the morphogenetic properties of the major cell types: mesenchyme and epithelia. Here resides my favorite example of the spirit of this book. Bard spends several pages (pp. 146-150) discussing “associative movement and 2-D pattern formation in vitro”-documenting the swirling patterns that tissue culture fibroblasts form when constrained by boundaries such as the edge of a plate or scratches in the plastic. Apparently, one can derive mathematical rules to which these patterns conform. This all seems interesting enough, but with no obvious connection to tissue organization. We are finally let in on the point-that fingerprints and the stripes on a zebra’s shoulder follow very similar topological rules, and that perhaps “boundaries” and the intrinsic “lining up of polarized cells” can help to explain such patterning. Furthermore, a footnote warns us that although Bard thinks this analysis (chiefly by Tom Elsdale and colleagues) can lend profound insight into patterning, at least one editor of a leading journal felt otherwise! Finally, in two brief chapters Bard tries (and, to some extent, succeeds) to formulate common properties that morphogenetic events share and to find a language with which to describe these processes. These chapters are important, for they unify the rest of the book and encourage one to think clearly about what one has read. Here, Bard draws on the analogy of a motorcyclist’s ability to defy gravity and climb the hemispheric “wall of death” to illustrate how the cyclist’s activity (cell movement) can lead to change (tissue organization). The final trajectory of the cyclist (the new state of tissue organization) depends not only on the physical forces that cause change, but also on the surfaces and boundaries encountered by the cyclist (or the cells). One interesting point here is that the end result of morphogenesis is not necessarily irrevocable or especially stable; the patterns formed by tissue culture fibroblasts are constant, but the cells continue to move. The book is well written, thoughtful, and entertaining, and clearly fills a need for an up-to-date account of the subject. In some sections frequent typographical errors are annoying, and the extensive index contains a major alphabetical glitch. Black-and-white .photographs are employed to illustrate points; these are adequate, but often diagrams would have been superior. Furthermore, some points are not well explained-including “traction” (the ef-
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fects that tension generated between cells and their surroundings can have on the surroundings [for example, to align the fibrils of the extracellular matrix and so create “tracks”]), which is defined only cursorily but later referred to extensively. Some sections are very brief: for example, the discussion of growth factors occupies one page (p. 174). However, since this topic gets tremendous attention in popular journals, its superficial treatment here is not a great deficit. The book is largely concerned with animal (particularly vertebrate) morphogenesis, with the essential exclusion of plants, algae, slime molds, and prokaryotes. A more serious query concerns the basic premise of this enterprise. Bard considers morphogenesis as largely or entirely separable from cell determination. I’m not sure that this is warranted, even with our limited knowledge of both processes. Clearly, in whole organisms the two usually accompany each other, and even in tissue culture models one often gets some morphogenesis along with tissue-specific gene expression (consider the formation of striated muscle fibers in vitro). Indeed, as more tissuespecific regulatory genes are isolated, a most intriguing challenge is to address whether (and if so, how) these genes contribute to multicellular organization. Nevertheless, the distinction between morphogenesis and determination, while artificial, does direct our attention to the less popular issues of development. Furthermore, Bard is clearly facile with molecular biology, as his final chapter shows; molecular biologists will particularly enjoy the section called “Storing Morphogenetic Information” (p. 262) in which we are asked what molecular biology can contribute to understanding tissue organization. In a sense this is a redundant question: the isolation of cell adhesion molecules and extracellular matrix components has already more than redeemed molecular biology in this regard. On the other hand, Bard is certainly correct to surmise that many aspects of morphogenesis are dependent on complex biochemistry, and not easily predictable by molecular biological analysis. In summary, I applaud Dr. Bard for taking the time to write this book (although I suspect he thoroughly enjoyed the exercise!). It will not gain the immediate popularity of Jonathan Slack’s From Egg to Embryo, another book in the same series, for it is more rambling and less general. Nevertheless, reading it will, I think, make molecular biologists view their work, and hopefully developmental biology in general, in new and interesting ways. Hazel
L. Sive
Fred Hutchinson Cancer Center Seattle, Washington 96104
Books Received Andemon, P. A. V. (1990). Evolution of the First Nervous Plenum Publishing Corp., New York. 423 pp. $95.00. Bills, D. D., and Kung, Butterworth-Heinemann,
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Cozzarelll, N. Ft., and Wang, J. C. (1990). DNA Topology and Its Biological Effects. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York. 480 pp. $97.00. Garner, R. C., and Hradec, J. (1990). Biochemistry of Chemical Carcinogenesis. Plenum Publishing Corp., New York. 267 pp. $65.00. Harrls, N., and Wllklnson, D. 0. (1990). In Situ Hybridisation: Application to Developmental Biology and Medicine. Cambridge University Press, Cambridge. 286 pp. $59.50. Kirk, T. K., and Chang, H.-M. (1990). Biotechnology in Pulp and Paper Manufacture. Butterworth-Heinemann, Stoneham, Massachusetts. 666 pp. $95.00. Konljn, T. M., Houslay, M. D., and van Haastert, P. J. M. (1990). Activation and Desensitization of Transducing Pathways. Springer-Verlag, Berlin. 320 pp. $114.00. Krulwlch, T. A. (1990). Diego. 569 pp. $110.00.
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Lambert, Y. W., and Laval, J. (1990). DNA Repair Mechanisms and Their Biological Implications in Mammalian Cells. Plenum Publishing Corp., New York. 667 pp. $129.50. Murphy, R. C., and Fltzpatrlck, F. A. (1990). Methods in Enzymology. Volume 187 Academic Press, San Diego. 683 pp. $85.00. New, R. R. C. (1990). Liposomes: A Practical sity Press, Oxford. 301 pp. $45.00.
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Oppanhelm, J. J., Powanda, M. C., Kluger, M. J., and Dinarello, C. A. (1990). Molecular and Cellular Biology of Cytokines. Wiley-Liss, New York. 570 pp. $150.00. Pasantes-Morales, H., Yartln, D. L., Shaln, W., and del RIO, R. M. (1990). Taurine: Functional Neurochemistry, Physiology, and Cardiology. Wiley-Liss, New York. 498 pp. $139.95. Pattereon, D., and Epstein, C. J. (1990). Molecular Genetics mosome 21 and Down Syndrome. Wiley-Lisa New York. $84.00.
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Ragaz, J., Simpson-Harren, L., Llppman, M. E., and Flsher, B. (1990). Effects of Therapy on Biology and Kinetics of the Residual Tumor. Part A: Pre-Clinical Aspects. Wiley-Liss, New York. 393 pp. $110.00. Ragaz, J., Simpson-Herren, L., Llppman, M. E., and Fleher, B. (1990). Effects of Therapy on Biology and Kinetics of the Residual Tumor. Part B: Clinical Aspects. Wiley-Lisa New York. 264 pp. $89.95. Stella, A. M. G., de veIlIs, J., and Peres-Polo, J. R. (1990). Regulation of Gene Expression in the Nervous System. Wiley-Liss, New York. 465 pp. $124.95. Wall, R. (1990). This Side Up: Spatial Determination in the Early Development of Animals. Cambridge University Press, Cambridge. 436 pp. $110.00. Wiley, D. C., Schlelf, R., Bloom, B. R., Horvltz, H. R., Fink, 0. R., and Noller, H. F. (1990). The Harvey Lectures. Series 84, 1968-1989. Wiley-Liss, New York. 157 pp. $48.00.