The configuration of the ascidian tadpole larva represents the most simplified and primitive chordate body plan. The present study revealed that Ciona intestinalis contains two hedgehog genes (Ci-hh1 and Ci-hh2), which are likely to be independent duplicate genes in this animal and ancestral to the three types of hedgehog gene of vertebrates. Ci-hh1 was expressed maternally and its maternal tra...

Transcriptional repression is a pervasive feature of animal development. Here, we employ live-imaging methods to visualize the Snail repressor, which establishes the boundary between the presumptive mesoderm and neurogenic ectoderm of early Drosophila embryos. Snail target enhancers were attached to an MS2 reporter gene, permitting detection of nascent transcripts in living embryos. The transge...

Furrow ingression in animal cell cytokinesis is controlled by phosphorylation of myosin II regulatory light chain (mRLC). In Caenorhabditis elegans embryos, Rho-dependent Kinase (RhoK) is involved in, but not absolutely required for, this phosphorylation. The calmodulin effector myosin light chain kinase (MLCK) can also phosphorylate mRLC and is widely regarded as a candidate for redundant func...

Partitioning ectoderm precisely into neurogenic and non-neurogenic regions is an essential step for neurogenesis of almost all bilaterian embryos. Although it is widely accepted that antagonism between BMP and its inhibitors primarily sets up the border between these two types of ectoderm, it is unclear how such extracellular, diffusible molecules create a sharp and precise border at the single...

Importation of animals or animal products cannot take place without some element of risk. Risk analysis is a blend of art and science and is a tool intended to provide decision-makers with an objective, repeatable and defensible assessment of the risks posed by a particular import proposal. Risk analysis comprises risk identification, risk assessment, risk management and risk communication. Exa...

All animal embryos pass through a stage during which developmental control is handed from maternally provided gene products to those synthesized from the zygotic genome. This maternal-to-zygotic transition (MZT) has been extensively studied in model organisms, including echinoderms, nematodes, insects, fish, amphibians and mammals. In all cases, the MZT can be subdivided into two interrelated p...

The cortex of fertilized Xenopus laevis eggs undergoes regional changes in its composition and morphogenetic activity during the first three divisions. Gray crescent and animal pole cortex of stage 1 (1-cell) and stage 4 (8-cell) embryos each contain a characteristic array of proteins. Implantation of pieces of cortex into the blastocoel of midblastula embryos was used to assay their inductive ...

Few treatments are known that perturb the dorsoventral axis of the sea urchin embryo. We report here that the dorsoventral polarity of the sea urchin embryo can be disrupted by treatment of embryos with NiCl2. Lytechinus variegatus embryos treated with 0.5 mM NiCl2 from fertilization until the early gastrula stage appear morphologically normal until the midgastrula stage, when they fail to acqu...

BACKGROUND The prairie vole (Microtus ochrogaster) is an emerging animal model for biomedical research because of its rich sociobehavioral repertoire. Recently, lentiviral transgenic technology has been used to introduce the gene encoding the green fluorescent protein (GFP) into the prairie vole germline. However, the efficiency of transgenesis in this species is limited by the inability to rel...

During the breeding season in Korea (September 1997 to April 1998), a goat embryo recovery and transfer program using a Korean native strain (Capra hircus aegagrus) was performed for the production of transgenic goats. Donors were synchronized with norgestomet implants and superovulated by a combined treatment with FSH and hCG. The treatment regime induced a consistent and efficient superovulat...