Posted on 31 March 2011

Book Review

Imaging in Developmental Biology, A Laboratory Manual is another outstanding and practical manual in the Cold Spring Harbor Laboratory Press's imaging series. I highly recommend this book as the textbook for a laboratory course at the undergraduate and graduate level. This is a laboratory manual and it will complement, but not replace, a full course in developmental biology.

First, I state the problem and then I provide the solution. A modern researcher in developmental biology may be highly skilled in a variety of modern imaging techniques, skilled in digital imaging processing, and technically competent in the design and construction of imaging instruments. Nevertheless, I posit that without a laboratory course on imaging in developmental biology, or extensive practical work under a skilled mentor's supervision, it is unlikely that the researcher will succeed. The reason is the plethora of technical details that involve specimen integrity, labeling, care and feeding, physiological regulation, and a large number of confounding effects due to the specimen care, labeling, and the untoward effects of the fluorescent labels or of the light incident on the specimen. The causes of failure can be placed into two categories: first the technical problems and second the problems of image analysis and interpretation. The problems in both categories can be mitigated by appropriate laboratory experience under the supervision of a person that is highly skilled in working with the specific biological specimen and with the specific imaging technique. In general, the set of biological and imaging skills are unique and are not readily transferable from organism to organism or from one imaging modality to another. However, there can be exceptions, and therefore I encourage an expanded knowledge of various techniques and specimens.

Imaging in Developmental Biology provides an excellent practical solution to this dilemma. The book's scope is broad and logically divided into four sections. Model systems covers Caenorhabditis elegans, Drosophila, zebrafish, Xenopus, chick, quail, and mouse. The section on Cells describes cell fate, differentiation, migration, and circuits in the nervous system. The Tissues and organs section describes the development of the notochord, the kidney, the heart, the eye. The Whole Embryo section describes cell lineage and expression profiling, optical projection tomography, microCT, magnetic resonance imaging, and light-sheet fluorescence microscopy. For a bit of perspective, look at the book Embryonic Development and Induction (1938) written by Hans Spemann, the German embryologist who received the Nobel Prize in 1935 for his work on embryonic induction by organizers. Clearly, creative developments of probes and imaging techniques have provided developmental biologists with truly revolutionary tools to advance their science.

This is a book of protocols. For each of the systems in the previous paragraph there are detailed protocols that are in the following categories: labeling, sample preparation, sample mounting and imaging, and image analysis. The protocols cover the imaging setup, the materials, the experimental methods, recipes, and a section on troubleshooting that described typical problems and their suggested solutions. The text is augmented by many colored illustrations and specimen images and reconstructions. In order to fully appreciate the three-dimensional images and the temporal development of specimens several movies are freely available from the book's Website. The standard appendices of the books in the imaging series are included as well as an index. Important appendices include: resources for live imaging of Drosophila, and Cautions which should be located in the front of the book. The book's chapters include extensive references and Websites for further study.

What are the unique and outstanding features of Imaging in Developmental Biology? The reader may ask the following question: why is it important to learn imaging techniques from such a variety of model systems, cells tissues, organs, and embryos? A related question could be: why learn some many imaging techniques when I am interested in a specific imaging modality. Imaging in Developmental Biology is not limited to optical imaging techniques; it included ultrasound, microCT, and magnetic resonance imaging. I previously stated that in general, specific technical details that are useful for a biological specimen or a specific imaging technique are not readily transferable and that is still true. An intrinsic and important value of the book and its associated course is to construct a broad knowledge base of biological and technical skills that span multiple biological specimens and multiple imaging modalities. Then and only then could the researcher optimally formulate their research questions, and then they could use their knowledge base to develop research strategies and tactics to approach their research problem. In some cases, it may be optimal to use more than one type of biological specimen, in other cases it may be beneficial use more than one imaging modality. The selection of an optimal imaging technique requires a careful and thoughtful evaluation of the following points: ease of use, technical complexity, cost to acquire the instrument, maintenance, size of biological specimen, stability of biological specimen, data acquisition time, requirements of genetic or extrinsic probes or indicators, probeless techniques, phototoxicity, photobleaching, physiological hemostasis, effects of overexpression of genetic fluorescent probes, effects of the imaging signal (light, ultrasound, X-rays, electric and magnetic fields) on the development of the specimen. It should be obvious that the nature of the biological question and research problem is what determines the choice of biological specimen and imaging modality; never should the available instrumentation and expertise with a particular biological specimen determine the research problem.

My perusal of the entire book permits me to state that the chapters are well written, the protocols are clear and written with sufficient detail, and the illustrations and images are extremely helpful to the reader. While I am not able to verify the workings of each protocol, I can assume that they are tested in courses and in the author's laboratory. Finally, I wish to point out in this review some aspects of the book's content that I find to be exceptional; unfortunately they are lacking or less distinct in many other imaging books. What I found to be impressive are the many sections of the text that describe and evaluate the limitations of the labeling, the specimen preparation, the specimen mounting and imaging, and the image analysis. These descriptions go far beyond the typical topics of photobleaching, phototoxicity, and non-physiological concentrations and conditions in the course of the experiments.

Each of the protocols and imaging techniques described in Imaging in Developmental Biology will affect the cells, tissues, organs, or the embryo that is being studied. Typically researchers are interested in investigating the gene expression, cell migration, proliferation, and differentiation, and these processes involve imaging over a period of time. The use of controls and the appropriate experimental design can isolate and minimize the untoward effects of the imaging technique on the normal cellular and organism functions and hopefully these effects can be excised from the interpretation of the experiments.

Throughout this book there are warnings and discussions about untoward effects of the protocols. I cite some prominent examples. On p. 13 the authors present a critical discussion of phototoxicity, the effect of aberration and light scattering, and problem of signal-to-noise-ratio. On p. 31 the authors provide insights on transgene expression and its limitations. On p. 82 the limitations of GFP-Fusion Proteins is examined and the reader is warned about GFP overexpression can result in abnormal protein localization. On p. 153 we are warned about cellular damage from transfection techniques. On p. 297 the authors present the advantages and limitations of various techniques for imaging cell migration. The cautious tone of the book is again evident on p. 443 where the discussion of anesthesia cautions the reader to conform to institutional and federal regulations regarding animal experimentation.

After taking a course in imaging in developmental biology the researcher is faced with a multitude of questions on instrument acquisition; should a commercial instrument be purchased or should the researcher construct an instrument. On p. 632 the authors present the options and the financial and the technical constraints in a thoughtful manner.

Imaging in Developmental Biology succeeds and fulfills the editor's goals that they stated in their introduction. Clearly, this book is a work in progress and hopefully the readers will solve important biological problems and perhaps contribute to future editions.