275nization during cortical rotation, the prime example of a symmetry-breaking process,
remains largely unknown. The cell movements underlying asymmetry in the mam-
malian blastocyst are similarly mysterious. Both of these areas would likely benefit
from advances in live imaging technology that are rendering the molecular activities
of cells and tissues more visible and quantifiable. In particular, new methods for cul-
turing and imaging different vertebrate embryos (e.g., Bedzhov and Zernicka-Goetz
2014 ; Keller et al. 2008 ) will likely provide novel insights into morphogenesis.
There have recently been rapid advances in whole genome analysis and genome
editing technology that will likely transform the study of developmental biology
and biology in general. Large-scale gene expression, chromatin analysis and pro-
teomics are becoming commonplace and should yield abundant material for data
science analysis. It is probably not a stretch to imagine that real-time whole tran-
scriptome analyses will also become technologically feasible in living cells in the
near future. TALEN and Cas9/CRISPR-mediated genome editing are also on the
verge of becoming routine, extending mutational analysis to many areas previously
intractable. Thus, in the foreseeable future, a variety of “-omics” data should be
readily available for any organism, and investigators will have the capability to
interrogate the function of any genomic region and immediately read out responses
in gene expression and cell behavior.
The lack of detailed genomic and genetic information and methodologies has
often been a barrier to work in many nontraditional model organisms. However,
newer technologies should soon allow the genetic analysis of axis formation and
other processes in organisms rationally chosen based on phylogenetic position or
other criteria based on the biological question. Indeed multiple related species could
be analyzed in parallel to capture extant variation in developmental mechanisms.
Such ideas are not new (Tzika and Milinkovitch 2008 ) but are much closer to real-
ization. Some interesting candidates for developmental analysis could include tree
shrews, owing to their similarity to primates, and echidnas, as an egg-laying mam-
mal model (Tzika and Milinkovitch 2008 ). The increased availability of human
embryonic stem cells is also leading to a better understanding of human develop-
ment. Gene regulatory networks can be analyzed in embryonic stem cells and
induced-pluripotent stem cells and tissue “organoids” are increasingly being used to
understand human organ development (e.g., McCracken et al. 2014 ). Certain ethical
considerations would have to navigated however to study human axis formation in
this way. Comparative studies of early development across all vertebrates could be
facilitated by reviving the idea of a “standardized vertebrate normal table” (Witschi
1956 ; Hopwood 2007 ). Such a standard series could be based on conserved gene
expression data, gene regulatory network organization and morphogenetic patterns.
Potential in-roads to such a project have already been made with the construction of
comparative drawings based on gene expression patterns, the “Molecular Haeckels”
(Elinson and Kezmoh 2010 ).
It is perhaps ironic that just as long-awaited sequenced genomes and targeted
genome editing technologies are becoming routinely available in organisms like fish
and amphibians, interest in the basic science of development in these organisms is
perceived to be waning in favor of human-centered translational research. It remains
6 Vertebrate Axial Patterning: From Egg to Asymmetry