The onset of myelination is early in Prkar1a-SCKO sciatic nerves. A, EM shows 1:1 SC-axon relations (asterisks) in control and Prkar1a-SCKO sciatic nerves at E18. Bottom, more myelin wraps were present in Prkar1a-SCKO sciatic nerves. B, Oct6 expression was increased in Prkar1a-SCKO sciatic nerves stained with anti-Oct6. C, MBP expression was increased in E18 Prkar1a-SCKO sciatic nerves. D, EM shows myelinated axons (asterisks) in Prkar1a-SCKO sciatic nerves at P0. There was a significant increase in myelinated axons in E18–P0 Prkar1a-SCKO nerves. For each genotype, n = 6 mice at E18–P0 (***p < 0.001, Student's t test). Error bars indicate ± SEM. E, MBP and Pmp22 expression were increased, whereas Krox20 was slightly decreased in Prkar1a-SCKO sciatic nerve lysates. Total ErbB3, P-Akt, and P-Erk1/2 were decreased in Prkar1a-SCKO sciatic nerve lysates by Western blot (n = 3). β-Actin was used as a loading control. Scale bars: A, 1 μm; B, C, 25 μm; D, 2 μm.