© Springer International Publishing Switzerland 2017 307
F. Pelegri et al. (eds.), Vertebrate Development, Advances in Experimental
Medicine and Biology 953, DOI 10.1007/978-3-319-46095-6_7
Chapter 7
Establishment of the Vertebrate Germ Layers
Wei-Chia Tseng, Mumingjiang Munisha, Juan B. Gutierrez,
and Scott T. Dougan
Abstract The process of germ layer formation is a universal feature of animal
development. The germ layers separate the cells that produce the internal organs
and tissues from those that produce the nervous system and outer tissues. Their
discovery in the early nineteenth century transformed embryology from a purely
descriptive field into a rigorous scientific discipline, in which hypotheses could be
tested by observation and experimentation. By systematically addressing the ques-
tions of how the germ layers are formed and how they generate overall body plan,
scientists have made fundamental contributions to the fields of evolution, cell sig-
naling, morphogenesis, and stem cell biology. At each step, this work was advanced
by the development of innovative methods of observing cell behavior in vivo and in
culture. Here, we take an historical approach to describe our current understanding
of vertebrate germ layer formation as it relates to the long-standing questions of
developmental biology. By comparing how germ layers form in distantly related
vertebrate species, we find that highly conserved molecular pathways can be adapted
to perform the same function in dramatically different embryonic environments.
Keywords Pander • Ectoderm • Mesoderm • Endoderm • TGF-beta • Fgf • Nodal •
Morphogen • Temporal gradient • Extraembryonic tissues • Teleost • Amniote •
Amphibian
7.1 Introduction
The world is about to observe the 200th anniversary of the publication of two papers
by Christian Heinrich Pander (1794–1865) in 1817 that mark the foundation of
modern developmental biology (Pander 1817a, b). Pander invented the language
W.-C. Tseng • M. Munisha • S.T. Dougan (*)
Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
e-mail: [email protected]
J.B. Gutierrez
Department of Mathematics, University of Georgia, Athens, GA 30602, USA
Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA