The spinal cord of early (18-20 hr) zebrafish embryos consists of a small number of neurons per hemisegment. The earliest neurons are identified and project growth cones that follow stereotyped, cell-specific pathways to reach their termination sites. We have studied the pathways taken by 4 of the early neurons in order to delineate the cells and structures their growth cones encounter during p...

During early neurogenesis, the floor plate plays an essential role(s) in the differentiation of the ventral portion of neural tube. In this study, we detected the specific distribution of unique glycoconjugate during the floor plate differentiation. Formalin fixed paraffin sections of BALB/c mice (10-14 embryonic days) were processed for histochemical studies using horseradish peroxidase-labell...

The floor plate is a group of specialized cells located in the ventral midline of the vertebrate neural tube. It plays important roles in neural tube development as a source of signalling molecules for dorsoventral patterning and axonal guidance (for reviews, see Jessell and Dodd, 1992; Dodd and Jessell, 1993). A floor plate-derived signalling molecule, Sonic hedgehog (Shh), which is a vertebra...

Netrin-1, a diffusible signal secreted by floor plate cells at the ventral midline of the vertebrate CNS, can attract ventrally migrating axons and repel a subset of dorsally migrating axons in the spinal cord and rostral hindbrain in vitro. Whether netrin-1 can act as a global cue to guide all circumferentially migrating axons is, however, unknown. Here, we show that netrin-1 can attract alar ...

During development, progenitors and post-mitotic neurons receive signals from adjacent territories that regulate their fate. The floor-plate is a group of glial cells lining the ependymal canal at ventral position. The floor-plate expresses key morphogens contributing to the patterning of cell lineages in the spinal cord. At later developmental stages, the floor-plate regulates the navigation o...

The establishment of the floor plate at the ventral midline of the CNS is dependent on an inductive signaling process mediated by the secreted protein Sonic hedgehog (Shh). To understand molecularly how floor plate induction proceeds we identified a Shh-responsive regulatory element that directs transgene reporter expression to the ventral midline of the CNS and notochord in a Shh-like manner a...

In the developing spinal cord, axons project in both the transverse plane, perpendicular to the floor plate, and in the longitudinal plane, parallel to the floor plate. For many axons, the floor plate is a source of long- and short-range guidance cues that govern growth along both dimensions. We show here that B-class transmembrane ephrins and their receptors are reciprocally expressed on floor...

By using the quail-chicken chimera system, we have previously shown that during development of the spinal cord, floor plate cells are inserted between neural progenitors giving rise to the alar plates. These cells are derived from the regressing Hensen's node or cordoneural hinge (HN-CNH). This common population of HN-CNH cells gives rise to three types of midline descendants: notochord, floor ...

During development of the vertebrate CNS, commissural axons initially grow circumferentially toward the ventral midline floor plate. After crossing the floor plate, they abruptly change their trajectory from the circumferential to the longitudinal axis. Although recent studies have unraveled the mechanisms that control navigation of these axons along the circumferential axis, those that result ...