Journal of Neuroscience, Vol 6, 1912-1917, Copyright © 1986 by Society for Neuroscience
Branching of sensory and sympathetic neurites in vitro is inhibited by treatment with taxol
PC Letourneau, TA Shattuck and AH Ressler
Branching of elongating neurites in vitro occurs by the division of a
growth cone into 2 or more daughter neurites. An important initial step is
a broadening of the growth cone with establishment of a quiescent central
growth cone margin. Within the spreading growth cone, microtubules and
associated neuritic components diverge and become oriented toward the
lateral protrusive margins of the leading edge (Letourneau, 1983). We have
found that a low concentration of the microtubule-stabilizing agent taxol
severely reduces the incidence of growth cone branching by cultured sensory
and sympathetic neurons from chick embryos. In the presence of taxol,
neurites are broader and have more microtubules than normally. Divergence
of microtubules entering the growth cone from the proximal neurite is
reduced in the presence of taxol, and quiescence of the central growth cone
margin is less frequent. We propose that a critical step in branching is
the separation and spreading of the neurite cytoskeleton by tensions
generated at the lateral margins of the edge of the growth cone. Because
taxol increases neurite size and microtubule content without increasing
protrusive activity to the same extent, tensions produced in the motile
leading edge are insufficient to spread the microtubules and associated
neuritic materials into separate arrays for nascent branches.