Figure 2.

ΔPDZ-Prx Peripheral Nerves Have an Ameliorated Phenotype Compared to Periaxin Nulls

(A) Teased fibers from control and mutant quadriceps nerves were stained by immunofluorescence with antibodies directed at periaxin (Prx), Drp2, and the cytoplasmic marker S100. Periaxin- and Drp2-stained appositions are disrupted in the mutant, as are the Cajal bands delineated by S100 staining. Scale bar represents 20 μm.

(B) Electron microscopy of transverse sections from control and mutant quadriceps nerves showing the presence of appositions (asterisks) in control but their absence in mutant myelinated fibers, resulting in a concentric ring of cytoplasm around the myelin sheath. Scale bar represents 1 μm.

(C) Onion bulb formations are much less abundant in ΔPDZ-Prx or wild-type nerves compared to periaxin-null (Prx^−/−) nerves at all ages examined (mean values ± SEM, n ≥ 3; ^∗∗∗p < 0.001).

(D) Comparison of semithin cross sections of quadriceps nerves from control and ΔPDZ-Prx mice at 3 and 24 weeks. At 3 weeks, ΔPDZ-Prx nerves appear normal, but by 24 weeks, there are numerous nerve fibers with myelin foldings. However, onion bulb structures with thin myelin, indicative of demyelination and remyelination, are infrequent (red arrowheads). Onion bulb structures were not detectable in control nerves. Scale bar represents 10 μm.

(E) Teased fibers from quadriceps nerves of 8-week-old mice were stained with fluorescent phalloidin to detect Schmidt-Lanterman incisures. ΔPDZ-Prx fibers had incisures that were morphologically similar to those in the control (arrowheads). In contrast, incisures were completely deranged in Prx^−/− nerves. Scale bar represents 50 μm.