Cell, Vol. 59, 955-958, December 22, 1989, Copyright 0 1989 by Cell Press

A Fertile Pair

The Cell Biology of Fertilization. Edited by H. Schatten and G. Schatten. San Diego: Academic Press. (1989). 404 pp. $85.00.

One of a cell biologist’s most useful tools is a predictable system or process. Fertilization is such a process, and bi- ologists have used it to study cellular structure and func- tion since the late 1800s. Thus, it is a challenge to produce a book on fertilization that is not instantly out of date. The editors and authors of The Cell Biology of Fertilization have succeeded, because they show how hypotheses are tested as they discuss sperm behavior and motility, the remodeling of the egg’s architecture, and ionic regulation and its controls. This book reviews the primary literature through 1988 in a style that communicates the excitement of science.

The first three chapters of The Cell Biology of fertiliza- tion concern the sperm, but ionic control is the subject that opens and closes the book, as Schackmann discusses the acrosome reaction and Epel considers egg ‘arousal: Both of these chapters crisply tease apart the sometimes murky subject of the independent and synergistic effects of pli and Ca2+. Schackmann discusses sperm ion chan- nels and their influence on activation; experimental tech- niques are explained beautifully (e.g., the use of channel blockers and the identification by antibodies of membrane proteins and their functions). Epel explicitly comments on what various experimental designs can tell us about acti- vation. For example, the fact that cells often use multiple mechanisms to control a specific cell function limits our analysis of inhibitor studies (p. 370). Schackmann points out that a better understanding is needed of the localiza- tion of different functions along the sperm’s surface; a broader exposition of this point might have considered the immunocytochemical mapping of the guinea pig sperm by Primakoff, Myles, and co-workers (J. Cell Biol. 704, 141- 149,1987; Nature 335,543-546,1988) or the fucoid sperm by Callow and his colleagues (Planta 776, 298-306‘1988). The Schattens have invited a lively chapter by Lardy and San Agustin on caltrin, a protein that, depending upon its conformational state, has opposing effects on calcium up- take into bovine sperm. Roberts’ description of amoeboid movement in nematode sperm, which depends upon a filamentous 14.2 kd protein, not actin (see also Sepsenwol et al., J. Cell Biol. 708, 55-66, 1989), serves as a reminder that there is more than one way to skin a cat, because this movement closely resembles the actin-dependent move- ment of cells such as fibroblasts (Heath, Nature 302, 532- 534, 1983).

The second section of the book revolves around cyto- skeletal topics. The chapters on intermediate filaments by Biessmann and Walter and nuclear lamins by Stricker et al. are descriptive but beautifully illustrated and probably represent growth areas in fertilization research. Additional

Book Reviews

study of the reorganization of intermediate filaments in the syncytial Drosophila embryo appears very promising, es- pecially if mutants affecting this process can be found. Longo reviews cortical granule exocytosis and sperm- egg membrane integration. The chapters on the cortex, the centrosome, and dispermic human fertilization might have been grouped more closely: modification of the cor- tex vis-&is positioning of the meiotic spindle relates to the discussion of centrosome function by Paweletz and Mazia, and Boveri’s work is remembered in both that chap- ter and Kola and Trounson’s discussion of polyspermy in the human egg. Dispermic fertilization in humans, as well as sea urchins and some algae, is lethal, indicating that centriolar inheritance in these organisms, unlike the rat, is probably paternal. Incidentally, I liked Paweletz and Ma- zia’s warning that artificial parthenogenesis is a risky sys- tem for studies of the centrosome.

Dent and Klymkowsky describe the cytoskeleton during oogenesis and early embryogenesis in Xenopus, and they present a protocol for immunocytochemical analysis of these opaque eggs that should be helpful in other sys- tems. This chapter will be appreciated by anyone who has become dizzy while considering the rotation of the frog’s axis of polarity. Scholey et al. review microtubule-based motors in the sea urchin egg, including dynein and kine- sin. They provide clear protocols for isolation of motor pro- teins but occasionally assume too much from the reader; the experimental function of AMP-PNP for example, should have been introduced earlier.

Shapiro et al. cogently discuss biochemical changes in the egg’s extracellular coat in sea urchins, amphibians, fish, and mammals. This is a nice comparison, because there are large variations in the extent of obvious morpho- logical changes after fertilization among the eggs of these organisms, yet important biochemical alterations occur in all of them, which represent the slow block to polyspermy. I enjoyed the speculation that the zygotes perivitelline en- vironment may be especially important in helping the em- bryo to develop in a germ-free environment; however, some embryos require bacteria for normaf development (Provasoli and Pinter, J. Phycol. 76, 196-201, 1980). The regulation by the egg of ovoperoxidase (a cross-linking enzyme) to prevent hazardous and undesirable oxidation inside the egg is also a nice textbook example of the beauty of evolution,

The last section on ionic controls contains an excellent chapter on G proteins by Turner and Jaffe. Although this chapter concentrates on regulation of oocyte maturation and fertilization, it has a very straightforward exposition of G proteins in general. As with so many of the chapters in this book, it is an analytical discussion of the data, pro and con, on the involvement of G proteins in both oogenesis and sperm activation of the egg. It concludes with enough unanswered questions to mobilize a substantial portion of Cells readership for the foreseeable future. How cellular water changes during fertilization in the sea urchin is dis- cussed by Zimmerman et al. and is echoed by Epel in thinking about how enzyme activities may be regulated

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postfertilization. Petzelt and Hafner discuss calcium and mitosis (“a mythos?“); they conclude that calcium is impor- tant (also see Henson, J. Cell Biol. 709, 149-161, 1969) but demonstrate problems in analysis of free Ca2+ with differ- ent probes.

The standard of writing in this book is very high; I no- ticed grammatical problems in only two of the chapters. Other important reviews are cited, and most chapters pro- vide a historical perspective of their topics. Many appropri- ate and high-quality micrographs are included. However, the term syngamy is misused throughout the book (begin- ning in the Preface, p. xviii) to define, not gamete fusion at fertilization (see p. 226 in E. B. Wilson, The Cellin Devel- opment and Heredity, 1925), but fusion of the egg and sperm pronuclei; this event is more accurately described as karyogamy or pronuclear fusion.

This is a fine book, but there are some missing pieces in the puzzle. One is the exciting information on acroso- mal protein in Urechis (Gould and Stephano, Science 234, 1654-1656, 1967) which integrates electrophysiological and biochemical approaches to the study of fertilization and has great promise for extending our knowledge of a sperm receptor beyond faith in its existence. Another omission is the absence of any detailed analysis of a plant system, a too-common fault in many recent books on cel- lular and developmental biology. In addition to work on the fucoid system previously mentioned, viable sperm cells have been isolated from the pollen of several angiosperms (see Wagner et al., J. Cell Sci. 93, 179-164, 1969), and Russell has found evidence for preferential fertilization of the egg by one of the sperm cells of Plumbago (PNAS 82, 6129-6132, 1965). There is also exciting information on fertilization in the green alga Chlamydomonas (Pasquale and Goodenough, J. Cell Biol. 705, 2279-2292, 1967; Goodenough, J. Cell Biol. 709, 247-252, 1969); the role of CAMP in loss of the cell wall, flagellar tip activation, cyto- skeletal mobilization, and enhancement of sexual agglu- tinability in Chlamydomonas would have been an instruc- tive addition to this volume. Furthermore, at least as much is known about sexual pheromones and gametic chemo- taxis in plants as in animals (Maier and Miiller, Biol. Bull. 770, 145-175, 1966). No review can be global in such an active field, but it is easy to see why many graduate stu- dents are impoverished in their view of experimental sys- tems and, indeed, are surprised to find that plants have sperm. Speaking of which, investigators trying to under- stand sperm function might consider a system in which sperm cells are larger than 10 urn: the flagellated sperm of some cycads (gymnosperms) are 230 pm x 300 f.rm.

The Cell Biology of Fertilization is an excellent source of detailed, up-to-date information on fertilization in many animal systems. Wilson and Loeb would find familiar themes but great progress and a portent of continued ba- sic discoveries about the cell.

Susan H. Brawley Department of General Biology Vanderbilt University Nashville, Tennessee 37235

The Molecular Biology of Fertilization. Edited by H. Schatten and G. Schatten. San Diego: Academic Press. (1969). 364 pp. $65.00.

The fertilization event, lasting but a few seconds in the life of an organism, triggers a cascade of changes that initiate the program of embryonic development. During this brief interaction, a microcosm of cell biological and molecular phenomena take place, and indeed a scientific career can be spent studying the events of these few seconds. The process of fertilization centers on cell-cell recognition, and the signal transduction events that ensue from this sperm-egg interaction include increases in intracellular calcium and pH with resultant changes in the cytoskele- ton, initiation of secretory events, activation of single- enzyme and multienzyme systems, and ultimately the turn-on of the cell cycle. These mitoses, however, are not simply a sequence of equivalent cell divisions but a highly programmed division pattern that yields an asymmetric distribution of cytoplasm. This asymmetry subdivides the embryo into differing nuclear-cytoplasmic domains that result in the formation of the germ layers and ultimately different cell types.

The editors of this volume have rightly chosen to con- sider fertilization from its origins to its consequences. As regards origins, there are articles in this book on the dif- ferentiation of the sperm and the egg, the unique phases of gametogenesis involving the meiotic (as opposed to the mitotic) cycle, and the nature of the controls that result in first the cessation of meiosis (often for many years, as in the human female) and then the reinitiation of meiosis and release of the egg, referred to as egg maturation and ovu- lation.

During fertilization itself, a variety of related cell-cell in- teractions occur, such as the release of substances from the egg that affect sperm motility, the alteration of the sperm surface by substances on the egg surface so it can specifically bind to the egg, and the actual fusion of the sperm with the egg. This is followed by the transformation of the sperm nucleus into the zygote nucleus, fusion of the sperm and egg nuclei, and subsequent initiation of DNA synthesis and mitosis. Long-term consequences include sperm-induced cytoplasmic movements, known as ooplas- mic segregation, that result in the localization of special- ized cytoplasms and the aforementioned asymmetric cy- toplasmic divisions.

Has the molecular biology of fertilization been proper- ly covered in this monograph? Before responding, one might first ask if there is indeed a molecular biology of this event. My reading indicates that there is only a small amount of such biology, which centers at the moment around the molecules involved in sperm-egg binding (e.g., adhesion molecules and their receptors) and those controlling the cell cycle (e.g., cyclins). It is perhaps semantic whether the other subjects covered should be dubbed molecular, but I suspect most readers would label the bulk of the articles in this monograph as cellular. Yet the book provides agood overview of the developing inter- face of a molecular and cell biology of fertilization.