Andrew Ransick

Learn More
Development of the body plan is controlled by large networks of regulatory genes. A gene regulatory network that controls the specification of endoderm and mesoderm in the sea urchin embryo is summarized here. The network was derived from large-scale perturbation analyses, in combination with computational methodologies, genomic data, cis-regulatory(More)
Vegetal plate specification was assessed in S. purpuratus embryos after micromere deletions at the 4th, 5th and 6th cleavages, by assaying expression of the early vegetal plate marker Endo 16, using whole-mount in situ hybridization. After 4th cleavage micromere deletions, the embryos typically displayed weak Endo16 expression in relatively few cells of the(More)
The glial cells missing regulatory gene of Strongylocentrotus purpuratus (spgcm) was proposed earlier to be the genomic target of Delta/Notch (D/N) signaling required for specification of the mesodermal precursors of pigment cells. Here, we show that microinjection of a spgcm antisense morpholino oligonucleotide results in larvae without pigment cells.(More)
Founder cells for most early lineages of the sea urchin embryo are probably specified through inductive intercellular interactions. It is shown here that a complete respecification of cell fate occurs when 16-cell stage micromeres from the vegetal pole of a donor embryo are implanted into the animal pole of an intact recipient embryo. Animal pole cells(More)
We have used whole mount in situ hybridization to analyze the pattern of expression of the gene Endo 16 in S. purpuratus embryos. The mRNA is first detectable at 18 h post-fertilization in the cytoplasm of blastomeres derived from the Veg2 6th cleavage tier. The number of Endo 16 positive cells increases gradually through the beginning of gastrulation, and(More)
Genes that are upregulated by LiCl treatment of sea urchin embryos and/or downregulated by injection into the egg of mRNA encoding an internal fragment of cadherin (Cad) were detected in a differential macroarray screen. The method was that recently described by J. P. Rast et al. (2000, Dev. Biol. 228, 270-296). Almost 10(5) clones from a 12-h cDNA library(More)
We present the current form of a provisional DNA sequence-based regulatory gene network that explains in outline how endomesodermal specification in the sea urchin embryo is controlled. The model of the network is in a continuous process of revision and growth as new genes are added and new experimental results become available; see(More)
This study concerns the organization of sites of specific DNA/protein interaction within the regulatory domain of the Endo16 gene of Strongylocentrotus purpuratus. Earlier work had displayed a complex pattern of expression of this gene during embryogenesis. Endo16 transcripts are confined to the definitive vegetal plate in blastula stage embryos; at(More)
In Volvox carteri development, visibly asymmetric cleavage divisions set apart large embryonic cells that will become asexual reproductive cells (gonidia) from smaller cells that will produce terminally differentiated somatic cells. Three mechanisms have been proposed to explain how asymmetric division leads to cell specification in Volvox: (a) by a direct(More)
An early set of blastomere specifications occurs during cleavage in the sea urchin embryo, the result of both conditional and autonomous processes, as proposed in the model for this embryo set forth in 1989. Recent experimental results have greatly illuminated the mechanisms of specification in some early embryonic territories, though others remain obscure.(More)