Figure 4.

CSF-1 deficiency leads to a substantial amelioration of neuropathy in peripheral nerves of Cx32def mice. (A) Light microscopy of representative semithin sections of lumbar ventral roots and (B) electron microscopy of representative ultrathin sections of femoral quadriceps nerves from 12-month-old wild-type, Cx32def/Csf1wt and Cx32def/Csf1op mice. Note prominent pathological alterations in Cx32def/Csf1wt mice, such as abnormally myelinated (thinly myelinated and demyelinated) axons, onion bulbs, periaxonal vacuoles and regeneration clusters. Such features were rarely seen in Cx32def/Csf1op mice and most of the myelinated profiles appeared nearly normal. Enlarged periaxonal collars (arrows) were amply present in both genotypes. Asterisks demarcate blood vessels. Scale bars = 20 µm in A; 5 µm in B. (C) Western blot analysis for the myelin proteins myelin-associated glycoprotein (MAG), myelin basic protein (MBP) and myelin protein zero (MPZ;P0) (and β-III tubulin as loading control) in sciatic nerve lysates from 12-month-old wild-type, Cx32def/Csf1wt and Cx32def/Csf1op mice. All analysed myelin proteins showed strongly reduced levels in sciatic nerves from Cx32def/Csf1wt mice compared with wild-type nerves, but only mildly reduced levels in nerves from Cx32def/Csf1op mice. (D) Electron microscopy of an enlarged periaxonal collar. The Schwann cell collar (arrow) filled with cytoplasm (cyt) containing vesicular inclusions protrudes into the axonal space (ax). M = myelin; scale bar = 1 µm. (E) Morphometric quantification of enlarged periaxonal collars in femoral quadriceps nerves from 6-month-old wild-type, Cx32def/Csf1wt and Cx32def/Csf1op mice (n = 4) failed to demonstrate a dependency of this mutation-specific hallmark from CSF-1 expression. Mann–Whitney U-test. P > 0.05.