Laminin α2β1γ1 (Lm211) modulates myelin thickness in Nrg1IIItg sciatic nerves.
(A) Postnatal day 16 (P16) electron micrographs of sciatic nerves of the indicated genotypes. (B) G-ratios were calculated from at least 150 myelinated axons per mouse (n = 3). Nrg1IIItg mice show decreased g-ratio, and Nrg1IIItg//Lama2−/− mice show an intermediate g-ratio between wild-type and Nrg1IIItg. Scatter plot display (C) or distribution (D) g-ratios of individual fibers as a function of their axon diameter. The g-ratio of double mutants is opposite between small and large fibers, and the increase in myelin thickness is mainly observed in small axons. (E) Distribution of the diameter of myelinated axons in the indicated genotypes at P16. (F, G) Examples of aberrantly myelinated axons in Nrg1IIItg//Lama2−/− mice. In F, axons smaller than 1 μm are surrounded by a thick myelin sheath. In G, examples of redundant myelin are shown. Bar = 2 μm in A, F, G. The numerical data used in B–E are included in S1 Data.