The Journal of Neuroscience, February 1, 2000, 20(3):1044-1055
Identification of an Invariant Response: Stable Contact with
Schwann Cells Induces Veil Extension in Sensory Growth Cones
Michael
Polinsky1,
Kenneth
Balazovich2, and
Kathryn W.
Tosney2
Departments of 1 Neurosurgery and
2 Biology, The University of Michigan, Ann
Arbor, Michigan 48109
Growth cones sense cues by filopodial contact, but how their
motility is altered by contact remains unclear. Although contact could
alter motile dynamics in complex ways, our analysis shows that stable
contact with Schwann cells induces motility changes that are remarkably
discrete and invariant. Filopodial contact invariably induces local
veil extension. Even when contacts are brief, veils always extend
before the filopodia retract. Contact at filopodial tips suffices for
induction. Moreover, veils extend significantly sooner than on
filopodia contacting laminin, which often detach without extending
veils. The overall behavioral responses of the growth cone, such as
increased area and turning, result from integrating multiple discrete
responses. Cycles of veil induction enlarge the growth cone and often
lead it onto the cell. Invariant veil induction is abolished by
blocking N-cadherin signaling. We propose an axonal
guidance model in which different guidance cues act by inducing
different but discrete and invariant responses.
Key words:
axonal guidance mechanisms; filopodia; G-proteins; growth
cones; guidance cues; N-cadherin; pathfinding mechanisms; Schwann-neurite interactions; sensory neuron guidance; veils
Copyright © 2000 Society for Neuroscience 0270-6474/00/2031044-12$05.00/0