Characterization of an amphioxus paired box gene, AmphiPax2/5/8: developmental expression patterns in optic support cells, nephridium, thyroid-like structures and pharyngeal gill slits, but not in the midbrain-hindbrain boundary region
Language English Country England, Great Britain Media print
Document type Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.
- MeSH
- Alternative Splicing MeSH
- DNA-Binding Proteins genetics MeSH
- Gene Expression MeSH
- Photoreceptor Cells, Invertebrate embryology MeSH
- Kidney embryology MeSH
- Evolution, Molecular MeSH
- Molecular Sequence Data MeSH
- Brain Stem embryology MeSH
- Multigene Family MeSH
- Chordata, Nonvertebrate embryology genetics MeSH
- Eye embryology MeSH
- Body Patterning MeSH
- Amino Acid Sequence MeSH
- Base Sequence MeSH
- Sequence Analysis, DNA MeSH
- Sequence Homology MeSH
- Thyroid Gland embryology MeSH
- Transcription Factors genetics MeSH
- Ear embryology MeSH
- Gills embryology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Comparative Study MeSH
- Names of Substances
- AmphiPax-2-5-8 protein, Branchiostoma floridae MeSH Browser
- DNA-Binding Proteins MeSH
- Transcription Factors MeSH
On the basis of developmental gene expression, the vertebrate central nervous system comprises: a forebrain plus anterior midbrain, a midbrain-hindbrain boundary region (MHB) having organizer properties, and a rhombospinal domain. The vertebrate MHB is characterized by position, by organizer properties and by being the early site of action of Wnt1 and engrailed genes, and of genes of the Pax2/5/8 subfamily. Wada and others (Wada, H., Saiga, H., Satoh, N. and Holland, P. W. H. (1998) Development 125, 1113-1122) suggested that ascidian tunicates have a vertebrate-like MHB on the basis of ascidian Pax258 expression there. In another invertebrate chordate, amphioxus, comparable gene expression evidence for a vertebrate-like MHB is lacking. We, therefore, isolated and characterized AmphiPax2/5/8, the sole member of this subfamily in amphioxus. AmphiPax2/5/8 is initially expressed well back in the rhombospinal domain and not where a MHB would be expected. In contrast, most of the other expression domains of AmphiPax2/5/8 correspond to expression domains of vertebrate Pax2, Pax5 and Pax8 in structures that are probably homologous - support cells of the eye, nephridium, thyroid-like structures and pharyngeal gill slits; although AmphiPax2/5/8 is not transcribed in any structures that could be interpreted as homologues of vertebrate otic placodes or otic vesicles. In sum, the developmental expression of AmphiPax2/5/8 indicates that the amphioxus central nervous system lacks a MHB resembling the vertebrate isthmic region. Additional gene expression data for the developing ascidian and amphioxus nervous systems would help determine whether a MHB is a basal chordate character secondarily lost in amphioxus. The alternative is that the MHB is a vertebrate innovation.
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GENBANK
AF053762, AF053763
