Zebrafish wnt4b expression in the floor plate is altered in sonic hedgehog and gli-2 mutants.

The floor plate of the neural tube serves an important function as a source of signals that pattern cell fates in the nervous system as well as directing proper axon pathfinding. We have cloned a novel zebrafish wnt family member, wnt4b, which is expressed exclusively in the floor plate. To place wnt4b in the context of known regulators of midline development, its expression was analyzed in the zebrafish mutants cyclops (cyc), floating head (flh), you-too (yot), and sonic you (syu). wnt4b expression in the medial and lateral floor plate are shown to be regulated independently: medial floor plate expression occurs in the absence of a notochord, while lateral floor plate expression requires a functional notochord, sonic hedgehog and gli-2.