Fig. 2: Reduction of NMNAT2 increases retinal ganglion cell susceptibility to injury.
From: NMNAT2 is a druggable target to drive neuronal NAD production
A Crossing mice heterozygous for Nmnat2 gene-trap alleles gtBay (predicted 50% silencing) or gtE (predicted 100% silencing) allowed Nmnat2 titration. In these mice, retinal Nmnat2 was depleted to (observed vs. expected based on allele penetrance) 80% (expected 75%; Nmnat2gtBay/+, n = 10), 39% (expected 50%; Nmnat2gtE/+, n = 12), or 10% (expected 25%; Nmnat2gtBay/gtE, n = 12) of normal levels relative to wild type controls (100%; Nmnat2+/+, n = 10). B RGC density was significantly lower in Nmnat2gtBay/gtE retina than in Nmnat2+/+ retina at 3 months without further change at 6 months (indicating a developmental loss). By 12 months of age, Nmnat2gtBay/gtE mice had significantly fewer RGCs than at 3 and 6 months, and this is stable to 22 months (indicating an additional early age-related decline). For Nmnat2+/+: 3 months, n = 6; 6 months, n = 8; 12 months, n = 8; 22 months, n = 8; for Nmnat2gtBay/gtE: 3 months, n = 6; 6 months, n = 8; 12 months, n = 8; 22 months, n = 6. Scale bar = 20 µm. C RGC density was significantly reduced in all Nmnat2 gene-trap allele mouse strains at 3 days ex vivo following RGC axotomy (RBPMS = specific marker of RGCs in the retina) relative to naïve controls (0 days ex vivo), and this was greatest in Nmnat2gtBay/gtE mice supporting a threshold of Nmnat2 loss beyond which RGC susceptibility to injury is increased (Day 0: Nmnat2+/+, n = 6; Nmnat2+/gtBay, n = 6; Nmnat2+/gtE, n = 6; Nmnat2gtBay/gtE, n = 6; Day 3: Nmnat2+/+, n = 8; Nmnat2+/gtBay, n = 6; Nmnat2+/gtE, n = 7; Nmnat2gtBay/gtE, n = 5; scale bar = 20 µm). For B and C, *P < 0.05, **P < 0.01, ***P < 0.001, NS = non-significant (P > 0.05); One-way ANOVA with Tukey’s HSD. For box plots, the centre hinge represents the median with upper and lower hinges representing the first and third quartiles; whiskers represent 1.5 times the interquartile range.
