The floor plate (FP) is a specialized ventral midline structure of the vertebrate neural tube that is required for CNS patterning, but how it is induced remains unresolved. One model proposes that it is formed by notochordal signals that induce overlying neural tube; another that the organizer generates midline precursor cells that produce the FP. Tian et al. now provide evidence for this latter model, on p. 3331, from a new temperature-sensitive (TS) zebrafish mutant. Cyclops is a zebrafish Nodal-related signalling factor, which in the TS mutant fails to function at 28°C, at which temperature FP development fails in mutant embryos. By shifting mutants between permissive and restrictive temperatures during development, the authors show that FP induction occurs during gastrulation and requires Cyc/Nodal signalling. Moreover, continuous Cyc signalling is required throughout gastrulation for complete ventral neural tube specification.

© 2003.
2003