Hensen’s Node: The Embryonic Organizer of the Chick
The chick embryo is a well-established model system for studying vertebrate embryogenesis. Its relatively large size during gastrulation and neurulation provides numerous and unique experimental possibilities. Today, techniques are available for culturing, manipulating, and mapping of avian embryos, tissues or single cells (Schoenwolf 2001). A wealth of information has been accumulated on pattern formation, cell lineages, cell specifications, organogenesis, tissue interactions, and inductive or responsive potentials. Avian versions of most developmental control genes are by now cloned and characterized. Their transcriptional responses to ectopically applied soluble factors or antagonists are often known. However, only a few of them have been functionally investigated after reintroduction into the living embryo via infection with viruses or the electroporation of cloned expression vectors. To date, lossof-function experiments have only rarely and with limited success been performed, using anti-sense or dominant negative strategies. Thus, with respect to genetic or pseudo-genetic approaches, the avian embryo as an experimental system still suffers from drawbacks. However, the availability of novel molecular tools such as morpholino oligonucleotides or small interfering RNAs indicates the ongoing search for novel experimental strategies.
KeywordsStein Meso Lawson Activin Milton
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