Fig. 3

Myrf ICKO blocks nearly all oligodendrocyte remyelination in recombined cells after SCI. a Illustration of transgenic mice used. Myrf ICKO and control mice were crossed with a mouse line that has a Rosa26mGFP (mT/mG) membrane-tethered GFP reporter that is Cre inducible. b Overview of injury epicenter at six WPI showing MBP, GFP, and NF200/SMI312 labeling. Representative areas from boxes are shown at higher magnification in c, d. c Single optical confocal sections stained with GFP for recombined cells, MBP to label myelin and NF-200/SMI312 to label axons in control mice. e Photomicrograph of individual oligodendrocyte processes wrapping around NF-200/SMI312 + axons and colabeling with MBP in control mice (yellow arrows). d In Myrf ICKO mice, there are few MBP+ GFP+ sheaths in the ventrolateral white matter. f Myrf ICKO mice have processes that wrap NF-200/SMI312+ but these processes typically do not express MBP (blue arrow). g Quantification of the density of newly generated myelin sheaths (mGFP+ MBP+ around NF200/SMI312+ axons) in spared tissue at two and six WPI. Control mice and Myrf ICKO animals do not differ at two WPI in their newly generated myelin sheath densities, but at six WPI control mice have a higher density of newly generated myelin sheaths compared to Myrf ICKO mice (F(1, 18) = 37.77 two-way repeated measures ANOVA, P < 0.001; two WPI Myrf ICKO vs. Control: P = 0.812 six WPI Myrf ICKO vs. Control: P < 0.001 Tukey’s post hoc test). h Quantification of the percentage of MBP+ sheaths around axons that are GFP+ (new myelin) at six WPI at the lesion epicenter. There are more new myelin sheaths in control mice relative to Myrf ICKO (df = 10, t = 10.69, P < 0.001, Student’s t test). i Quantification of GFP+ processes, which completely wrap axons but fail to express detectable MBP and likely represent ensheathment by oligodendrocyte lineage cells reveals no statistical differences at six WPI (df = 10, t = 1.665, P = 0.127, Student’s t test). j, k The ventrolateral white matter at two WPI showing few GFP+ MBP+ myelin sheaths in both control animals and Myrf ICKO mice. ^***P ≤ 0.001, ns non-significant. Scale bar = 100 µm (b) and 10 µm (c, d, j, k). Error bars are mean ± SEM