The elaboration of the complex vertebrate brain is thought to depend partly on a unique signalling centre known as the midbrain-hindbrain boundary (MHB)organiser. But now (on p. 285), Kaoru Imai and colleagues report that an MHB-like organising structure patterns the central nervous system (CNS) of the invertebrate sea squirt, Ciona intestinalis. Ciona is a tunicate, which, like vertebrates, belong to the chordate phylum. Its larvae closely resemble frog tadpoles and possess a simplified CNS with at least four morphologically distinct compartments. By characterising gene expression and function in the Ciona larvae CNS, the researchers assemble a provisional gene regulatory network (GRN) for CNS development in Ciona. This GRN reveals that an FGF, called FGF8/17/18, has a central role in CionaCNS compartmentalisation, similar to that of FGF8 in patterning the vertebrate MHB. Based on these findings, the researchers propose that FGF8-mediated CNS patterning was present in the last common ancestor of tunicates and vertebrates, and served to delineate two regions of the chordate brain.
Ciona brain patterning pushes back boundaries Free
Ciona brain patterning pushes back boundaries. Development 15 January 2009; 136 (2): e204. doi:
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