A key stage in the development of higher animals is the specification of endodermic and mesodermic cells. A complex genetic regulatory network underlies this early differentiation process. At Caltech, Eric Davidson's group and collaborators are trying to unravel this network in sea urchin embryos (Strongylocentrotus purpuratus). From their website:
"At present over 40 genes have been linked into this [the endo-mesoderm specification] network. The architecture of the network is emerging from an interdisciplinary approach in which computational analysis is applied to data emerging from gene expression knockouts, genomic sequence, and gene discovery projects, combined with experimental embryology. We are isolating both regulatory and downstream genes required for skeletogenesis, for territorial specification, utilizing high density arrayed cDNA libraries. A predictive model which indicates expected inputs and outputs of key cis-regulatory elements has been built and is being tested as the relevant cis-regulatory systems are found. "
For information on the biology of endo-mesoderm specification, and the techniques used to elucidate the underlying mechanisms, see http://www.cco.caltech.edu/~mirsky/endomeso.htm and http://www.cco.caltech.edu/~mirsky/summary.htm, on
Experiments suggest a structure for the endo-mesoderm specification network, and NetBuilder is used to put the experimentalists hypotheses to the test, by simulating the behaviour of the hypothetical network. Some of the results are shown on the following pages. To get the pictures shown here, the network on the NetBuilder canvas was copied onto the Windows clipboard, and from there into these pages.