A greater threshold for myelination is also seen in FAK-deficient mice. (Left) Representative electron micrographs show a reduction in the frequency of small myelinated axons in optic nerve sections of P16-P21 FAK knockout mice compared with wild-type mice. 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 dnβ1 mice. A polynomial trendline was adjusted to the data. A reduced percentage of myelination across all axon diameter intervals is present in FAK knockout compared with wild-type mice (**, P < 0.01).