βII spectrin-deficient Schwann cell myelinated axons. A, Cross sections of sciatic nerves from Control (WT, Sptbn1f/f); and cKO, Cnp-Cre;Sptbn1f/f mice at P13, 14 weeks, and 60 weeks of age. Scale bars, 5 μm. B, Scatter plots of g-ratio (y-axis) in relation to axon diameter (x-axis) of individual fiber in sciatic nerves. g-ratios: Control (0.6693 ± 0.0617, mean ± SD; n = 219 axons) and cKO (0.7131 ± 0.0695, mean ± SD; n = 316 axons) at P13; Control (0.697 ± 0.0578, mean ± SD; n = 203 axons) and cKO (0.6871 ± 0.0588, mean ± SD; n = 187 axons) at 14 weeks of age; and Control (0.6447 ± 0.0653, mean ± SD; n = 315 axons) and cKO (0.6284 ± 0.0698, mean ± SD; n = 314 axons) at 60 weeks of age. Data were collected from two control (1 WT and 1 cHet) and three cKO mice at P13; two control (WT) and two cKO mice at 14 weeks, and three control (WT) and three cKO mice at 60 weeks of age. Approximately 100 axons were analyzed per mouse.