Symptomatic SOD1^G93A mice, sciatic nerve.

<p>Non-radioactive in situ hybridization for rRNA (green) yields strong signals in 2 myelinated axons (arrows), delineated by Nile red fluorescence of myelin (red). In the left axon, the small signal inside the myelin sheath (arrowhead) most likely corresponds to ribosomal RNA localized in ad-axonal Schwann cell cytoplasm or in Schwann cell cytoplasm between the myelin membranes (e.g. clefts of Schmidt-Lantermann), which has previously been suggested as a transfer route for ribosomes from Schwann cells to axons (Court et al, J Neurosci 2008, 28∶11024–11029). The signal outside the myelin sheets (arrowheads) corresponds to ribosomes in the peri-axonal Schwann cell cytoplasm. Please note that most axons do not show a hybridization signal, but show a strong Schwann cell signal (arrowheads), confirming the specificity of the ISH. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087255#pone.0087255.s002" target="_blank">Figure S2</a> for optical sections of this area. Bar, 5 µm.