Induction of the floor plate at the ventral midline of the neural tube is one of the earliest events in the establishment of dorsoventral (d/v) polarity in the vertebrate central nervous system (CNS). The secreted molecule, Sonic hedgehog, has been shown to be both necessary and sufficient for this induction. In vertebrates, several downstream components of this signalling pathway have been ide...

In vertebrates the neural tube, like most of the embryonic organs, shows discreet areas of programmed cell death at several stages during development. In the chick embryo, cell death is dramatically increased in the developing nervous system and other tissues when the midline cells, notochord and floor plate, are prevented from forming by excision of the axial-paraxial hinge (APH), i.e. caudal ...

Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3) in commissural axon guidance using a knockout (KO) mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptor...

Ventral midline cells at different rostrocaudal levels of the central nervous system exhibit distinct properties but share the ability to pattern the dorsoventral axis of the neural tube. We show here that ventral midline cells acquire distinct identities in response to the different signaling activities of underlying mesoderm. Signals from prechordal mesoderm control the differentiation of ros...

We have examined the regulation of transcription factor gene expression and phenotypic markers in developing chick sympathetic neurons. Sympathetic progenitor cells first express the bHLH transcriptional regulator Cash-1 (a chicken achaete-scute homologue), followed by coordinate expression of Phox2, a paired homeodomain protein, and GATA-2, a zinc finger protein. SCG10, a pan-neuronal membrane...

Members of the Slit family are large extracellular glycoproteins that may function as chemorepellents in axon guidance and neuronal cell migration. Their actions are mediated through members of the Robo family that act as their receptors. In vertebrates, Slit causes chemorepulsion of embryonic olfactory tract, spinal motor, hippocampal and retinal ganglion cell axons. Since Slits are expressed ...

Tissue and urokinase-type plasminogen activators are serine proteases with highly restricted specificity, their best characterised role being to release the broad specificity protease plasmin from inactive plasminogen. It has frequently been suggested that these, and similar proteases, are involved in axonal growth and tissue remodelling associated with neural development. To help define what t...

Despite extensive studies, there are still many unanswered questions regarding the mechanism of hedgehog signaling and the phylogenic conservation of hedgehog function in vertebrates. For example, whether hedgehog signaling in vertebrates requires smoothened is unclear, and the role of hedgehog activity in zebrafish is controversial. We show that inactivation of smoothened by retroviral inserti...

Ventral cell fates in the central nervous system are induced by Sonic hedgehog, a homolog ofhedgehog, a secreted Drosophila protein. In the central nervous system, Sonic hedgehog has been identified as the signal inducing floor plate, motor neurons, and dopaminergic neurons. Sonic hedgehog is also involved in the induction of ventral cell type in the developing somites. ptc is a key gene in the...

Synthesis of regional plate movements reveals a major reorganization of global plate motion from Mesozoic to Cenozoic patterns that occurred primarily during the Eocene epoch (53.5 to 37.5 m.y.B.P.). The reorganization involved reorientation of relative plate motions with large N-S components into large E-W components, continuation of pre-existing E-W sea floor spreading, initiation of new E-W ...