Biology Reference
In-Depth Information
A
0
5
¢
0
²
5
¢
05
²
5
¢
10
²
p
f
f
1
c
f
1
n
8
¢
45
²
8
¢
50
²
20
¢
55
²
22
¢
1
f
c
fMNP
fMNP
B
C
60
120
100
*
40
80
60
*
*
20
40
*
*
*
20
0
0
Veil
initiations
Filopodial
initiations
% Veils
moving
Filopodia
% Filopodia
moving
Unloaded magnet (
+
)
cMNP magnet (
+
)
fMNP magnet (
-
)
fMNP magnet (
+
)
Figure 2.6 Altering signaling endosome localization induces distinct changes in growth
cone dynamics. (A) A representative lamellar growth cone loaded with fMNP signaling
endosomes was immobilized during and after a 3-min exposure to a 15 pN force (start at
time 0). Within 5 min, neurite elongation and central domain advance halted and lamel-
lar motility in the peripheral (p) domain immobilized. The central domain (c) and distal
neurite (n) widened (compare 0
0
to 5
0
). However, filopodial (f) protrusions with small
lamella (l) protruded from the central domain and then extended above the
immobilized lamellar domain before cycling retrogradely to the base of the growth
cone where they were absorbed. During peripheral domain immobilization, fMNP pun-
cta were detectable and moved dynamically in the central domain (compare 8
0
45
00
-
8
0
50
00
). Approximately, 15 min after removing the magnet, protrusive activity at the
leading edge resumed in concert with central domain advance. Time in minutes (
0
)
and seconds (
00
) is indicated. Scale bar is 5 mm. (B) A focal 15 pN force halted neurite
elongation in neurites loaded with fMNPs, but not unloaded or cMNP-loaded RGCs.
The neurite growth rate was unaltered in fMNP-loaded RGCs in the absence of a focal
magnetic force. (C) In fMNP-loaded RGCs, lamellar and filopodial initiations, the number
of moving lamella and filopodia, and the number of filopodia were all reduced by a focal
magnetic force, compared to control RGCs with a magnetic force or fMNP-loaded RGCs
without a magnetic force. (Values normalized to activity during the first 5 min of record-
ing. In (B) and (C), n¼at least 3/condition; *p
<
0.0001.) Reprinted with permission from
the Proceedings of the National Academy of Sciences (
Steketee et al., 2011
).
