Figure 5. OL-Kir4.1 is dispensable for remyelination, but critical for long-term axon maintenance after WM demyelinating injury.
OL-Kir4.1 function was studied in short- (A–C) and long-term remyelination (D–F) after lysolecithin-induced focal demyelination to ventrolateral spinal WM tracts. Mice were euthanized and perfused at two survival time points corresponding to days post lesioning (dpl, n = 4 for each time point and genotype): 14 dpl (corresponding to P94, representing new myelin sheath formation) and 60 dpl (corresponding to P140, full remyelination). Densities of intra-axonal mitochondria were increased in cKO-1 (176 axons from 4 mice) versus control animals (230 axons from 4 mice) at 14 dpl and circularity/swelling of intra-axonal mitochondria was higher in cKO-1 (79 axons from 4 mice) versus controls (141 axons from four mice; A-B). Note high-magnification images of representative mitochondria in A indicating enlarged mitochondria in axons from cKO-1 versus control lesioned tissue. Conversely, loss of OL-Kir4.1 did not affect g-ratios and axon diameters in cKO-1 (176 axons from 4 mice) versus control mice (230 axons from four mice) (C). At 60 dpl, cKO-1 mice exhibited pronounced WM damage during long-term remyelination with presence of enlarged and degenerating axons (highlighted in green and yellow) as well as increased numbers of swollen intra-axonal mitochondria (D). Numbers of intra-axonal mitochondria were increased in cKO-1 versus control mice 60 dpl but densities of mitochondria were not different due to enlargement of lesion axons and thus relative lower mitochondria densities in cKO-1 axons; intra-axonal mitochondria were more circular in cKO-1 (90 axons from 4 mice) mice as compared to controls (88 axons from 4 mice) at 60 dpl (E). Remyelination was efficient and not different between cKO-1 (139 axons from 4 mice) and control mice (152 axons from 4 mice) at 60 dpl, however, enlarged axons were observed in cKO-1 mice as compared to controls (F). Mann-Whitney tests were performed in B–C and E–F; *p≤0.05, p=0.69 (C). Data are presented as mean ±s.e.m in B–C and E–F.
Figure 5—figure supplement 1. Short- and long term remyelination efficiencies in chronic OL-Kcnj10 loss-of-function .
