Pathfinding by neuronal growth cones in grasshopper embryos I. Divergent choices made by the growth cones of sibling neurons

Journal ArticleWe are interested in how the growth cones of identified neurons navigate in the central nervous system of the grasshopper embryo. The behavior of identified growth cones was observed as a function of developmental time by (i) periodically removing embryos from synchronized clutches of eggs and (ii) filling identified neurons in the central nervous system with the fluorescent dye Lucifer Yellow

Pathfinding by neuronal growth cones in grasshopper embryos: IV. The effects of ablating the A and P axons upon the behavior of the G growth cone

Journal ArticleIn the companion paper (Bastiani, M. J., J. A. Raper, and C. S. Goodman (1984) J. Neurosci. 4: 2311-2328), we show that as the G growth cone reaches its choice point and turns anteriorly on the A/P fascicle, its filopodia demonstrate selective affinity for the A/P fascicle as compared to the other approximately 25 longitudinal axon fascicles, and within the A/P fascicle itself, G's filopodia selectively contact the P axons as compared to the A axons

Pathfinding by neuronal growth cones in grasshopper embryos: II. Selective fasciculation onto specific axonal pathways

Journal ArticleIn the previous paper (Raper, J. A., M. Bastiani, and C. S. Goodman (1983) J. Neurosci. 3: 20-30) we showed that the growth cones of two sibling neurons, the G and C cells, follow the same route in the developing grasshopper neuropil until they reach a stereotypic choice point. Here their growth cones diverge from each other as G turns and extends anteriorly and C turns and extends posteriorly. In this paper we show that the G and C growth cones fasciculate and extend in opposite directions upon a specific bundle of four axons

Pathfinding by neuronal growth cones in grasshopper embryo: III. Selective affinity of the G growth cone for the P cells within the A/P fascicle

Journal ArticleThe growth cone of the G neuron selectively fasciculates upon specific axon bundles in a stereotypic sequence as it navigates through the developing central nervous system of the grasshopper embryo. It turns and extends anteriorly in the contralateral neuropil of the second thoracic ganglion at a specific choice point where it fasciculates with the A/P axon bundle which contains the axons of the A1, A2, P1, and P2 neurons

Olfactory Sensory Axons Expressing a Dominant–Negative Semaphorin Receptor Enter the CNS Early and Overshoot Their Target

AbstractSensory axons extend from the chick olfactory epithelium to the telencephalon well before the maturation of their target, the olfactory bulb. During a waiting period of several days, olfactory axons arrive and accumulate outside the CNS while the bulb differentiates beneath them. Semephorin-3A is expressed in the telencephalon during this period and has been proposed to prevent their entry into the CNS. We show that the misexpression of a dominant–negative neuropilin-1 that blocks SEMA-3A-mediated signaling in olfactory sensory axons induces many of them to enter the telencephalon prematurely and to overshoot the olfac tory bulb. These results suggest that chemorepellents can prevent the premature innervation of immature targets

Olfactory Sensory Axons Expressing a Dominant–Negative Semaphorin Receptor Enter the CNS Early and Overshoot Their Target

AbstractSensory axons extend from the chick olfactory epithelium to the telencephalon well before the maturation of their target, the olfactory bulb. During a waiting period of several days, olfactory axons arrive and accumulate outside the CNS while the bulb differentiates beneath them. Semephorin-3A is expressed in the telencephalon during this period and has been proposed to prevent their entry into the CNS. We show that the misexpression of a dominant–negative neuropilin-1 that blocks SEMA-3A-mediated signaling in olfactory sensory axons induces many of them to enter the telencephalon prematurely and to overshoot the olfac tory bulb. These results suggest that chemorepellents can prevent the premature innervation of immature targets

SDF1-Induced Antagonism of Axonal Repulsion Requires Multiple G-Protein Coupled Signaling Components That Work in Parallel

SDF1 reduces the responsiveness of axonal growth cones to repellent guidance cues in a pertussis-toxin-sensitive, cAMP-dependent manner. Here, we show that SDF1's antirepellent effect can be blocked in embryonic chick dorsal root ganglia (DRGs) by expression of peptides or proteins inhibiting either Gαi, Gαq, or Gβγ. SDF1 antirepellent activity is also blocked by pharmacological inhibition of PLC, a common effector protein for Gαq. We also show that SDF1 antirepellent activity can be mimicked by overexpression of constitutively active Gαi, Gαq, or Gαs. These results suggest a model in which multiple G protein components cooperate to produce the cAMP levels required for SDF1 antirepellent activity

The detection and quantification of growth cone collapsing activities

Growth cone guidance during development, as well as axonal extension in neural repair and plasticity, is strongly regulated by both attractive (growth-promoting) and repulsive (growth-inhibiting) guidance molecules. The growth cone collapse assay has been widely and successfully used for the identification and purification of molecules that are repulsive to growth cones or inhibit axonal outgrowth. Here we provide a detailed description of the assay, which uses the morphology of the growth cone after exposure to a test protein as the readout. With the modifications detailed in this protocol, this assay can be used for the biochemical enrichment of proteins with a collapsing activity and for the identification of a collapsing activity of a known protein or gene. This assay does not require very specialized equipment and can be established by every lab with experience in neuronal cell culture. It can be completed in 3 d

Inhibiting PLC blocks antirepellent activity induced by expression of a constitutively active Gα_q.

<p>DRGs were transfected with expression plasmids for Citrine (control, empty bars), Citrine and QL Gα_q (grey bars), or Citrine and QL Gα_s (black bars). Expression of QL Gα_q makes growth cones insensitive to sema3A unless the PLC blocker U73122 (20 nM) is also present. Growth cones expressing QL Gα_s are insensitive to sema3A in both the absence and the presence of U73122. *, p<0.002.</p