Table Of ContentResults and Problems in Cell Differentiation
Series Editor: 40
w. Hennig
Springer-Verlag Berlin Heidelberg GmbH
Lilianna Solnica-Krezel (Ed.)
Pattern Formation
in Zebrafish
With 95 Figures, 17 in Color
Springer
Dr. Lilianna SOLNICA-KREZEL
Dept. of Biological Sciences
Vanderbilt University
VU Station B 351634
Nashville, TN 37235-1634
USA
ISBN 978-3-642-07811-8 ISBN 978-3-540-46041-1 (eBook)
00110.1007/978-3-540-46041-1
Library of Congress Cataloging-in-Publication Data
Pattern formation in zebrafish 1 Lilianna Solnica-Krezel (ed.).
p. cm. -(Results and problems in cell differentiation; 40)
Includes bibliographical references (p. ).
1. Zebra dania - Development. 2. Pattern formation (Biology) I. Solnica-Krezel,
Lilianna, 1961- II. Series.
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Preface
What makes an ideal model system to study embryonic development? The
answer to this question has varied in the course of scientific quest, depending
on the available experimental approaches. Yet, at the beginning of the new
millennium, most of the mainstream model organisms have one feature in
common, they are amenable to genetic analysis. Indeed, the genetic approach
has proven remarkably effective in the dissection of complex biological
phenomena, starting with the regulation of the lactose operon in Escherichia
coli, the decision between the lysogenic and lytic cycles of the lambda phage
and the yeast cell cycle control. The genetic screens for mutations affecting
embryonic development of a fruit fly, Drosophila melanogaster, carried out by
Christiane Niisslein-Volhard, Eric Wieschaus and Edward Lewis, marked the
turning point in experimental approaches to embryonic development of more
complex organisms. The resulting mutants facilitated identification of the key
regulatory molecules, while their phenotypic classes hinted at the underlying
regulatory mechanisms. This work not only provided a paradigm for genetic
dissection of other developmental processes, but also inspired many budding
embryologists throughout the world.
Soon thereafter, George Streisinger noted that, among vertebrates, the
zebrafish, Danio rerio, offered many features facilitating the dissection of
nervous system development and function. Among these, transparency of the
embryo, ease of husbandry, and the highly prolific nature make the zebrafish
a good genetic model system. The pioneering work of George Streisinger was
continued by his colleagues Chuck Kimmel, Judith Eisen, John Postlethwait,
Monte Westerfield, and Jim Weston in Eugene, Oregon (USA). These studies
laid the methodological foundation for using the zebrafish, and their experi
mental and intellectual elegance sparked an interest in this model system in
the scientific community.
The last decade witnessed an explosion of zebrafish research, culminating
in the zebrafish joining the ranks of "mainstream models for human develop
ment and disease". This was the result of a concerted, multi-pronged, collabo
rative effort between many laboratories throughout the world. Two large-scale
genetic screens for zygotic embryonic lethal mutants in the Niisslein-Volhard
laboratory in Tiibingen (Germany) and the Driever laboratory in Boston (USA)
yielded thousands of mutations in hundreds of genes. The results of these
screens, which were published in a special volume of Development in 1996,
VI Preface
demonstrated the feasibility of the large-scale, forward genetic approach in
zebrafish and in vertebrates, and promised that all aspects of embryonic
development are susceptible to mutations. Concurrent work in the Postleth
wait laboratory in Eugene (USA) and in the Jacob, Fishman, and Driever
groups in Boston (USA) assembled the first zebrafish genetic maps, thus paving
the road towards molecular characterization of identified mutant loci. Simul
taneously, the efforts of tens and then hundreds of labs focused on isolating
the zebrafish homologues of known genes from other vertebrate and inverte
brate organisms, providing crucial descriptions of normal development,
generating genomic resources, and methods for sophisticated cellular and
embryological analyses, as well as devising new mutagenesis procedures. These
methods have been described in a two-volume set of Methods in Cell Biology,
published in 1999 by Academic Press, providing a much needed resource for
an increasing number of scientists using zebrafish.
In this book, we present the current view of the mechanisms underlying the
early patterning and morphogenetic processes in zebrafish. The book was
written 5 years after the conclusion of the first, large-scale screening effort, at
a time when phenotypic and molecular characterizations of many mutant loci
had been accomplished. We deliberately avoided describing methods and tools,
our main objective being to provide a synthesis of what we have learned so far,
and to identify the key questions for the next decade of research.
The book is divided in four parts with the first two parts devoted to the
early inductive and morphogenetic events, respectively. The third part focuses
on patterning and differentiation of neural tissues, whereas the fourth part
discusses aspects of organogenesis. We start with the earliest inductive and
patterning events in the zebrafish blastula and gastrula. The chapter by Takuya
Sakaguchi, Toshiro Mizuno, and Hiro Takeda is concerned with the formation
and developmental role of the yolk syncytial layer. This fascinating, extra
embryonic structure serves not only as a source of energy and supplies for the
developing embryo, but also has important roles in patterning the overlying
blastoderm. The next two chapters describe our current understanding of the
formation and patterning of the germ layers, with David Kimelman and Alex
Schier focusing on mesoderm, whereas Rachel Warga and Didier Stainier
address endoderm development. They review insights from zebrafish into
Nodal signaling that in many ways contributed to the rapid progress in this
field. Formation of the Spemann-Mangold gastrula organizer and its roles
in embryonic polarity specification are the topics of the chapter by Masahiko
Hibi, Toshio Hirano, and Igor Dawid. Matthias Hammerschmidt and Mary
Mullins further elaborate the problem of anteroposterior and dorsoventral
patterning with special emphasis on the role of bone morphogenetic proteins
in this process. This part culminates with Chris Wright and Marnie Halpern
considering the origin of left-right embryonic asymmetry. There are several
designed overlaps between these chapters, highlighting the interconnectedness
of the early inductive events. Indeed, zebrafish studies clearly show that
Nieuwkoop center activity encompasses not only the dorsal yolk syncytial
Preface VII
layer, but also dorsal marginal blastomeres. Furthermore, Spemann-Mangold
organizer activity is not confined to dorsal mesoderm but is also present in
ectoderm and possibly endoderm.
The second part of the book presents our current understanding of gastru
lation, the morphogenetic process transforming the two-dimensional blastula
fate map into the three-dimensional vertebrate body plan. From the chapter by
Don Kane and Richard Adams, we learn about epibolic movements that spread
blastoderm around the yolk cell, and about the internalization of mesodermal
and endodermal precursors. Lila Solnica-Krezel and Mark Cooper address the
convergence and extension movements that narrow germ layers from back to
belly, while elongating them from head to tail. It becomes clear that fish gas
trulation entails a complex repertoire of cell behaviors, some not encountered
in the well-characterized frog gastrula. In the last chapter of this part, Erez Raz
and Nancy Hopkins describe specification of primordial germ cells in the blas
toderm margin and their fascinating migration towards the future gonad.
These chapters highlight the notion that combining mutational analyses with
tracking cell movement behaviors in living embryos is a powerful approach
for the dissection of morphogenetic processes.
The third part of the book, focusing on neural development, begins with an
overview of early neural patterning by Steve Wilson, Michael Brand, and Judith
Eisen. Work on zebrafish revealed the existence of new signaling centers that
pattern neuroectoderm and provided novel insights into how spatiotemporal
regulation of canonical W nt signaling regionalizes neuroectoderm along the
anteroposterior axis. In the next chapters, Robert Kelsh and Dave Raible
discuss specification of the neural crest, whereas Bruce Appel and Ajay Chitnis
address the mechanisms determining neuronal cell identity. The chapter by
Christine Beattie, Michael Granato, and John Kuwada concludes this part with
a discussion of axon guidance mechanisms.
Amenability to investigate early embryonic patterning was the initial attrac
tion of using the zebrafish. However, in the last part of this book, we hope to
illustrate that this system also has much to offer for studying organogenesis.
Caroline Brennan, Sharon Amacher, and Peter Currie discuss formation of
somites and their subsequent patterning and differentiation. Genetics of
cardiovascular system development and function are described by Brant
Weinstein, Debbie Yelon, and Mark Fishman. Although the zebrafish and
mammalian kidney differ significantly, lain Drummond makes a case that
analyses of zebrafish pronephros will provide important insight into the early
stages of mammalian kidney development. The book closes with a discussion
of mechanisms involved in eye development by Stephen Easter and Jarema
Malicki.
The current knowledge of the morphological, cellular, and genetic events of
early zebrafish development summarized in this volume establishes a solid
foundation for the next phase of scientific inquiry. New generations of genetic
screens for mutations altering fluorescently marked organs and tissues, new
methods of cell tracking, implementation of morpholino antisense oligonu-
VIII Preface
cleo tide technology to provide a greatly needed reverse genetic tool, and finally
the emergence of the zebra fish genome sequence will allow us to pose more
sophisticated questions in the next decade. We hope that this book will serve
as a useful resource in this endeavor.
The making of this book in many ways reflects the collegial atmosphere and
synergistic interactions among the zebrafish scientific community, being the
fruit of discussions and collaborative efforts between researchers from many
countries. It is our hope that this volume will help maintain the tradition of
collaboration and scientific discourse in the zebrafish community.
Lila Solnica-Krezel
March 2002
Acknowledgements. I would like to express my gratitude to all colleagues who contributed to the
book, first for embracing the idea of collaborative chapters, next for sharing their knowledge,
valuable time and effort during writing, and finally for patiently bearing with a somewhat over
eager editor. Springer-Verlag editors Sebastian Granderath and Ursula Gramm were very under
standing and helpful with coordinating and editing this volume. Sponsorship of publishing color
illustrations in the book by Gene Tools, LLC, is greatly appreciated. Special thanks to my friends
Bruce Appel and Mark Cooper, and to my family, for encouraging me to take on this ambitious
task and for their continued support. I am also grateful to the members of my research group for
their infinite enthusiasm for zebrafish development, and for graciously tolerating my chronic lack
of time during the last year. Work in my laboratory and efforts on this volume have been sup
ported by grants from National Institutes of Health, March of Dimes Birth Defects Foundation
and Pew Scholars Program in Biomedical Sciences.
Contents
I. Germ Layer Formation and Early Patterning
Formation and Patterning Roles of the Yolk Syncytial Layer
Takuya Sakaguchi, Toshiro Mizuno, Hiroyuki Takeda
1 Introduction ........................................... 1
2 Formation of the YSL .................................... 3
3 Epibolic Movement and the YSL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Dorsal Determinants in Teleost Yolk Cell . . . . . . . . . . . . . . . . . . . . . 6
5 Determinants Function in the YSL and Dorsal Blastomeres ...... 8
6 The Role of the YSL in Mesoderm and Endoderm Formation . . . . . 11
7 Localized Inducing Activities Within the YSL . . . . . . . . . . . . . . . . . . 12
8 Is Visceral Endoderm in Mammal Equivalent to Teleost YSL? . . . . . 12
9 Searching for Genes Specifically Expressed in the YSL .......... 14
Mesoderm Induction and Patterning
David Kimelman, Alexander F. Schier
1 The Origin of Mesoderm ................................. 15
2 Induction of Mesoderm by Intercellular Signals ............... 17
3 Nodal Signaling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 Dorsal-Ventral Patterning of the Mesoderm .................. 21
5 Anterior-Posterior Patterning of the Mesoderm ............... 24
6 Wnt Signals in Mesoderm Patterning. . . . . . . . . . . . . . . . . . . . . . . . 26
7 Future Directions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
The Guts of Endoderm Formation
Rachel M. Warga, Didier Y. R. Stainier
1 Endoderm Formation During the Blastula Period . . . . . . . . . . . . . . 28
1.1 Location of Endodermal Progenitors. . . . . . . . . . . . . . . . . . . . 28
1.2 Early Topographic Map of Endodermal Organs ........... 29
1.3 Organs of Ambiguity: the Hypochord and Forerunner Cells. . . 30
1.4 Cell Behavior of Endodermal Progenitors .... . . . . . . . . . . . . 31
1.5 Genes Involved in Endoderm Formation . . . . . . . . . . . . . . . . . 31
1.6 The Nodal Factors and Cofactors: Cyclops, Squint,
and One-Eyed Pinhead .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
x Contents
1.7 Nodal Versus Bmp Activity. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
1.8 Nodal-Independent, Oep-Dependent Cell Motility ......... 33
1.8.1 Oep as a Component of EGF Signaling. . . . . . . . . . . . . . 33
1.9 Effectors of Nodal Signaling: Casanova, Bonnie
and Clyde, and Faust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 4.
1.9.1 The Endodermal Phenotypes of cas, bon andfau
Mutants and the Expression of These Genes in
the Blastula ................................... 34
1.9.2 Cas Is Sufficient To Convert Mesoderm
into Endoderm ................................ 36
1.10 A Molecular Pathway Leading to Endoderm Formation ..... 37
2 Endoderm Formation During the Gastrula Period ............. 39
2.1 Formation of the Endodermal Layer ..................... 39
2.2 Spatial Allocation of Endodermal Precursors .............. 39
2.3 Genes Involved in Endoderm Formation:
cas, bon, and fau Revisited ............................. 41
2.3.1 Cas May Regulate sox17 Directly ................... 42
2.3.2 The FoxlForkhead Transcription Factors .. . . . . . . . . . . . 42
2.3.3 Other Genes Expressed in the Endoderm ............ 43
2.4 Regional Expression in the Endoderm at the End
of Gastrulation ...................................... 43
2.5 Further Thoughts on Endodermal Patterning . . . . . . . . . . . . . . 45
3 Pharyngeal Pouch Endoderm Versus Digestive Tract Endoderm .. 46
4 Conclusions and Prospects ................................ 47
Organizer Formation and Function
Masahiko Hibi, Toshio Hirano, Igor B. Dawid
1 Introduction ........................................... 48
2 Dorsal Determinants and the Maternal W nt Signal .. . . . . . . . . . . . 50
2.1 Dorsal Determinants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
2.2 A Maternally Derived Signal Activating the W nt Pathway .... 51
3 The Nieuwkoop Center and Organizer Induction .............. 54
3.1 Non-ceIl-autonomous Induction of the Organizer .......... 54
3.2 bozozok/dharma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 5. . . . . .
3.3 Nodal-Related Genes, squint and cyclops. . . . . . . . . . . . . . . . . . 57
3.4 Cooperative Roles of bozldha and sqt in the Induction
of the Organizer ..................................... 60
3.5 vega/vox/vent ....................................... 61
3.6 Induction by the Nieuwkoop Center Versus Cell-Autonomous
Establishment of the Organizer ......................... 61
4 The Organizer .......................................... 63
4.1 Is the Embryonic Shield the Fish Organizer? . . . . . . . . . . . . . 63. .
4.2 Organizer Genes ..................................... 64
4.3 chordino, nogginl, twisted gastrulation, and ogon . . . . . . . . . . . 65
