FIGURE 4

The microbiota induces temporal changes in myelin growth and integrity. (A) Electron micrographs of axons in the mPFC of germ‐free (GF) and conventionally‐raised (CON) mice. Scale bar, 1 µm. (B) Total number of myelinated axons in the mPFC of GF and CON mice throughout the early life developmental timepoints. (C) Average axon diameter of myelinated axons in the mPFC of GF and CON mice at P21. (D) Representative images of myelin abnormalities (arrowheads) in GF male mice at P21. Scale bar, 1 µm. (E) Proportion of axons with and without outfolding and unravellings per mm² in the mPFC of GF and CON mice during the early developmental timepoints. (F) Average inner tongue thickness in GF and CON mice at P21. (G) Scatter plot of mean inner tongue thickness per axon diameter in the PFC of GF and CON mice at P21. (H) Representative electron micrographs of GF and CON mice at P21. (Green; inner tongue region). Scale bar, 0.2 µm. (I)Average number of laminae per myelinated axon in the mPFC of GF and CON mice during the early developmental timepoints. (J) Average myelin thickness in GF and CON mice at P21. (K‐L) Myelin thickness versus axon diameter in the PFC of GF and CON mice at P21. Data presented as Mean ± SEM. Sample size: Early Development: n = 3 mice/group, >50 axons/per mouse. Microbiota; *p < 0.05, **p < 0.01, ***p < 0.001, Sex; #p < 0.05, ##p < 0.01. Detailed statistical analysis can be found in Supplementary Table S1.