Brachyury downstream notochord differentiation in the ascidian embryo
- Hiroki Takahashi,
- Kohji Hotta,
- Albert Erives,
- Anna Di Gregorio,
- Robert W. Zeller,
- Michael Levine, and
- Nori Satoh
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan ; Division of Genetics, Department of Molecular and Cellular Biology, University of California at Berkeley, Berkeley, California 94720 USA; Department of Biology, University of California at San Diego, La Jolla, California 92093-0347 USA
Abstract
The ascidian tadpole represents the most simplified chordate body plan. It contains a notochord composed of just 40 cells, but as in vertebrates Brachyury is essential for notochord differentiation. Here, we show that the misexpression of theBrachyury gene (Ci-Bra) of Ciona intestinalisis sufficient to transform endoderm into notochord. Subtractive hybridization screens were conducted to identify potentialBrachyury target genes that are induced upon Ci-Bramisexpression. Of 501 independent cDNA clones that were surveyed, 38 were specifically expressed in notochord cells. These potentialCi-Bra downstream genes appear to encode a broad spectrum of divergent proteins associated with notochord formation.
