Fig. 5

Re-growing phenomenon in a dystrophic axon. (a-d), Maximum projection of a stack of images taken in the supragranular layers of the somatosensory cortex of the APP-PS1 mouse at four different time points (two-photon microscopy). To facilitate the visualization of the axon of interest, only those optical sections where this axon was present were used for the maximum projections (32 sections in a, 30 in b, 10 in c and 15 in d; z-step: 1 μm). Panels a-d correspond to the same regions and days as those also illustrated in Fig. 1d-g. In day 61 (c), the distal part of the axon (white arrowheads) was lost just before the dystrophic part (dys 9, blue arrowhead in b). In day 68 (d), the axon starts to re-grow (red arrowheads). The inset in d shows the growth cone. (e-h), Schematic representation from images a-d, respectively, showing the axon of interest (green) and the re-growth segment (red). (i, j), Maximum projection of a stack of lower magnification images (89 sections in i and 98 in j; z-step: 0.7 μm), showing that the new axon segment (in d) can re-grow (red arrowheads) longer distances over time (re-growth segment: 73.9 μm in i and 104.5 μm in j). The square delimits the size of the regions shown in a-d. (k, l), Schematic representation from images i-j, respectively, showing the axon of interest (green) and the re-growth segment (red). Note that the re-growth axonal segment has changed its trajectory whereas the original axon segment maintains the original trajectory. The days shown refer to the number of days after day 0 (when imaging began). Scale bar (in l): 24 μm in a-h, 11.6 μm in d (inset) and 20.6 μm in i-l