Ethan Bier
The Coiled Spring: How Life Begins
2000
Cold Spring Harbor Laboratory Press
ISBN 0-87969-563-3

 

 

 

Contents

Preface

Chapter 1: The Central Dogma of Biology

The “central dogma”—that DNA, the heritable geneticmaterial, is copied into RNA, which directs the synthesis ofprotein—is a basic tenet of life. How this idea guided importantdiscoveries in developmental biology is described using examples ofthe Gurdon experiment, which proved that all cells in a frog containthe same genetic information; the nature of heritable mutations; andthe Mangold-Spemann experiment, which showed that a specialized regionof the frog embryo directs the formation of the nervous system.

Chapter 2: Molecular Methods for Analyzing Development

Techniques developed during the past 30 years have provided powerfultools for analyzing development. The most important of these—genecloning, methods for showing gene activity in developing embryos,and methods for analyzing and manipulating gene activity—aredescribed.

Chapter 3: Establishing the Primary Axes of Fruit FlyEmbryos

Establishing a plan or pattern for development of the fertilized eggis the key event in producing a differentiated embryo with differenttissue types. This process in the fruit fly is described using theground-breaking work of Eric Wieschaus, Christiane Nüsslein-Volhard,Gerd Jürgens, and Ed Lewis who found the genes that are requiredfor normal development by looking for mutants in which development wasabnormal.

Chapter 4: Patterning Fly Appendages and Eyes

Assembly of the adult fruit fly during metamorphosis is the focus here,particularly the development of fly wings, legs, and eyes. Theseprocesses are explained by describing the small set of genes thatdefine the primary axes of the wing, linking the formation of an adultstructure to earlier events in embryonic development, and discussingthe question of whether or not there are “master” genes thatdirect the formation of eyes.

Chapter 5: Establishing the Primary Axes of VertebrateEmbryos

Although higher on the evolutionary scale, vertebrate embryos usemany of the same genes as the fly embryo does to set up the primarybody axes and tissue types. And even more remarkable is the fact thatvertebrate genes involved in early embryonic development can replacetheir fruit fly counterparts in developing flies and vice versa. Theexperiments that revealed these astonishing facts and theirimplications are discussed.

Chapter 6: Patterning Vertebrates Appendages and Eyes

Here again is the unexpected finding that genes involved in definingadult structures such as appendages and eyes are the same invertebrates and flies. The evolutionary implications of thesimilarities of fly and vertebrate development are discussed, and themost recent common ancestor of flies and vertebrates is reconstructed.

Chapter 7: Establishing the Primary Axes of PlantEmbryos

Using the mustard plant embryo as an example, important differencesbetween plant and animal development are illustrated. The polarizationof the plant embryo along the shoot-to-root axis, as well as radialorganization, is shown using analysis of mutant plants that generateabnormal embryos. Similarities between plant and animal developmentare also discussed.

Chapter 8: Patterning Plant Appendages

The formation of the plant equivalent of appendages—flowers,fruits, and leaves—are described. Topics include: how flowerbuds develop into four basic organ types, Goethe’s inference thatall organs of the flower are modified forms of leaves (he was right!),and the finding that while very different genes in plants and animalscontrol formation of flat structures such as leaves or wings, thesegenes work by surprisingly similar mechanisms.

Chapter 9: The Future of Biology and Man

We are very rapidly making progress in understanding how genes controldevelopment and other human characteristics. The social implicationsof these discoveries—how we think of ourselves as humans and howthese discoveries can change our nature—are considered usingtopics such as the Human Genome Project, which is determining thecomplete genetic blueprint of humans, the implications of ournewfound knowledge of the genetics of human disease and health, andgenetic engineering of plants and animals. How the world of sciencefiction views these topics is also considered.

Bioboxes

Landmark progress in science is made by pioneering individuals.Those responsible for some of the key discoveries in developmentalbiology are highlighted in “Bioboxes” that appear throughoutthe text. These scientists represent the human side of the wonderfuldiscoveries described in this book.

	John Gurdon Hilde Mangold Johann Wolfgang von Goethe Ed Lewis Christiane Nüsslein-Volhard Eric Wieschaus Mike Levine Sean Carroll Antonio Garcia-Bellido	Gary Struhl Matthew Scott William McGinnis Cliff Tabin Gerd Jürgens Elliott Meyerowitz Enrico Coen Marty Yanofsky

I undertook writing The Coiled Spring because now is an opportune time to provide the general science reader with an account of the rapidly unfolding field of developmental biology. Several factors contribute to this timeliness. First, the field is at the point where many of the general principles are well understood. This is by no means to say that we have answered all of the interesting questions. Quite to the contrary, many exciting discoveries remain to be made. But we do have a good idea about the outline of how development works, and this emerging story should be of significant interest to anyone curious to know how a fertilized egg smaller than the head of a pin makes a person, a fly, or a plant. One of the most unexpected and profound findings of the field has been the discovery that the basic mechanisms guiding development are the same in apparently disparate organisms such as flies and humans.

Another reason for bringing the field of development to the attention of a more general audience at this point is that our new understanding of developmental mechanisms is already beginning to have a great impact on the world in which we live. As a result, a basic knowledge of this field is important for all who are interested in shaping our common future. I hope this book will serve its intended purpose by familiarizing the reader with classic experiments in developmental biology, some of the cutting-edge research that explains these classic observations in simple mechanistic terms, and the implications of these discoveries for the future.

Many people have contributed to this book. First, there are all of the scientists in the field of developmental biology from the time of Goethe to the present. In addition to the many investigators working actively on topics covered in this book, there are yet greater numbers of impassioned scientists who work long into the night hours to unravel many other equally interesting mysteries about development. These latter topics have not been discussed in this book only because of space limitations. I am particularly indebted to colleagues whom I pestered mercilessly with questions about their fields, including Marty Yanofsky, Detlef Weigel, Kathy Barton, Laurie Smith, Phil Benfey, and David Kimelman. I also express my gratitude to those who kindly agreed to be featured in the short biographical sketches scattered throughout the text. The "biobox" subjects were all asked to respond to a set of similar questions, and, invariably, they gave insightful and heartfelt responses. For me, reading and then organizing the comments of these accomplished individuals was one of the most interesting and rewarding parts of writing this book. The single most obvious outcome of this query was that questions such as "What are the most important ingredients in scientific discovery?" evoked a wide range of opinions and commentary. The diversity of views on such topics underscores the fact that scientists are individuals and approach science from many different perspectives, employing a variety of distinct strategies and styles. There may be more ways to study embryos than there are ways for embryos to develop!

I also thank the scientific reviewers of this book who took the time to make valuable and critical comments on the first draft of the book. In addition, I thank my father Jesse Bier; my colleagues at the University of California, San Diego; Marty Yanofsky, Bill McGinnis, Randall Johnson, Georgiana Zimm, Larry Reiter, and Diane Ingles; and Detlef Weigel of the Salk Institute, for reading drafts of the book or various chapters and making insightful comments. These reviewers helped define the focus and made excellent suggestions about the organization of topics.

Thanks are also due to the people at Cold Spring Harbor Laboratory Press for their help, especially Inez Sialiano and Jan Argentine in the Development Department and Pat Barker and Denise Weiss in the Production Department. Likewise, I was fortunate to have the assistance of Meghan Scott, a dedicated UCSD undergraduate, who helped compile the glossary. I also thank Dan Ang, who put in many hours preparing the plates of original data, and members of my lab for putting up with this project. Most of all, I thank Judy Cuddihy, my tireless, good-natured editor at Cold Spring Harbor Laboratory Press, and friend, for all of her varied efforts and encouragement during the lengthy series of steps from start to finish on the book.

Finally, I am most grateful to my wife Kathryn Burton and close friend Marty Yanofsky for their constant encouragement and support during the course of conceiving and writing this book. I'm sure they are quite happy that the ordeal is over and that the coiled spring has sprung!