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Abbreviations
AP Anteroposterior, Anterior-to-posterior
AVE Anterior visceral endoderm
BMP Bone morphogenetic protein
CRD Cysteine-rich domain
DEP domain Dishevelled, Egl10, Pleckstrin
DFC Dorsal forerunner cell
DIX domain Dishevelled, Axin
DV Dorsoventral, Dorsal-to-ventral
dYSL Dorsal yolk syncytial layer
EMT Epithelial-to-mesenchymal transition
EpiSC Epiblast stem cells
ES Embryonic stem
EVL Enveloping layer
FGF Fibroblast growth factor
GPCR G protein-coupled receptor
HMG High mobility group
ICM Inner cell mass
MAPK Mitogen-activated protein kinase
MBT Mid-blastula transition
MPF Maturation promoting factor
PCP Planar cell polarity
PDZ domain Postsynaptic density protein (PSD95), Disc large tumor suppressor
(Dlg1), and zonula occludens1 protein (ZO-1)
PMZ Posterior marginal zone
TALEN TAL-effector nuclease
TE Trophectoderm
Tgfb Transforming growth factor beta
UV Ultraviolet irradiation
6.1 Introduction
Bilaterality is a central feature of animal body organization. In certain invertebrates,
such as some insects and cephalopods, this feature is determined by the structure of
the egg itself (Wilson 1928 ), but vertebrates and many other animals define the
plane of bilateral symmetry de novo in each embryo. In vertebrates, this plane is
ultimately defined by the formation of the generalized vertebrate tissues, the dorsal
neural tube, notochord and somites. The vertebrate body axis fully forms during
gastrulation, following the internalization of axial mesendoderm at the future dorsal
midline of the embryo (Fig. 6.1). This event initiates at the dorsal (upper) lip of the
forming blastopore, the importance of which was first clearly recognized by
D.W. Houston