Local protein synthesis in growth cone guidance -- not true??

[James Zheng]

While a pile of previous studies have shown that local protein
synthesis (PS) and degradation are required for growth cone guidance
to a selected number of guidance cues, a recent paper from Paul
Letourneau's lab indicates that this may not be true. Using chick DRG
cells, they show that in the presence of cycloheximide or anisomycin,
ephrin-A2, slit-3, and semaphorin3A still induced growth cone collapse
and loss of actin filaments, nerve growth factor (NGF) and
neurotrophin-3 still induced growth cone protrusion and increased
filamentous actin, and sensory growth cones turned toward an NGF
source. See the link for this paper: http://www.jneurosci.org/cgi/content/full/29/3/638.

While I can not comment on the growth cone collapse data, I have taken
a close look at their turning results (Fig.6) and here is what I see:
no turning. Please see the image entitled "Letourneau turning data
analysis.jpg" for details.

Therefore, for me, the conclusion that local PS is not required for
turning does not have experimental evidence to support.