Figure 2. Genetic regulation of nerve injury-induced neurodegeneration. a, Relative motoneuron numbers (ratio between lesioned and contralateral sides; base 10 logarithm) in DA, PVG, F1, and F2 populations, with the median indicated. b, Micrographs of cresyl violet counterstained spinal cord sections demonstrating increased loss of motoneurons in the DA strain compared with PVG. Scale bar, 0.5 mm. Higher magnification micrographs of the lesioned side of the cord are shown to the right. Scale bar, 0.2 mm. c, Genome-wide LOD score plot for linkage to neurodegeneration in the F2 population. Threshold for significant linkage at 95% CI (dashed line) and the location of VRA1 and VRA2 are given. d, LOD score plot of the VRA1 QTL on rat chromosome 8. Dashed line indicates threshold for significant linkage at 95% CI. e, Survival of motoneurons (base 10 logarithm) in the F2 population stratified for genotype at the max marker of VRA1 (D8Rat205), demonstrating reduced survival in rats homozygous for the DA allele. Lines indicate the median. f, Micrographs of cresyl violet counterstained sections from representative animals homozygous for the DA allele (DA/DA), homozygous for the PVG allele (PVG/PVG), and heterozygous (DA/PVG) in VRA1 (D8Rat205). Scale bar, 0.5 mm. Higher magnification micrographs of the lesioned side are shown to the right. Scale bar, 0.2 mm. g, LOD score plot for VRA2 QTL at the centromeric end of chromosome 5 in the F2 population. Dashed line indicates threshold for significant linkage at 95% CI.