Dnβ3 mice show no evidence of altered axon diameter threshold for myelination. (Left) Representative electron micrographs of optic nerve sections of P17 wild-type and dnβ3 transgenic mice show no differences. Bar: 1 µm. (Right) Representative graph from one litter shows the percentage of myelinated axons with respect to axon diameter at 0.1-µm intervals for wild-type and dnβ3 mice. A polynomial trendline was adjusted to the data. The axon diameter threshold for myelination is unaffected in dnβ3 transgenic mice.