Neogenin neutralization prevents photoreceptor loss in inherited retinal degeneration
Jason Charish, … , Rod Bremner, Philippe P. Monnier
Jason Charish, … , Rod Bremner, Philippe P. Monnier
Published March 16, 2020
Citation Information: J Clin Invest. 2020;130(4):2054-2068. https://doi.org/10.1172/JCI125898.
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Research Article Neuroscience

Neogenin neutralization prevents photoreceptor loss in inherited retinal degeneration

Abstract

Inherited retinal degenerations (IRDs) are characterized by the progressive loss of photoreceptors and represent one of the most prevalent causes of blindness among working-age populations. Cyclic nucleotide dysregulation is a common pathological feature linked to numerous forms of IRD, yet the precise mechanisms through which this contributes to photoreceptor death remain elusive. Here we demonstrate that cAMP induced upregulation of the dependence receptor neogenin in the retina. Neogenin levels were also elevated in both human and murine degenerating photoreceptors. We found that overexpressing neogenin in mouse photoreceptors was sufficient to induce cell death, whereas silencing neogenin in degenerating murine photoreceptors promoted survival, thus identifying a pro-death signal in IRDs. A possible treatment strategy is modeled whereby peptide neutralization of neogenin in Rd1, Rd10, and Rho P23H–knockin mice promotes rod and cone survival and rescues visual function as measured by light-evoked retinal ganglion cell recordings, scotopic/photopic electroretinogram recordings, and visual acuity tests. These results expose neogenin as a critical link between cAMP and photoreceptor death, and identify a druggable target for the treatment of retinal degeneration.

Authors

Jason Charish, Alireza P. Shabanzadeh, Danian Chen, Patrick Mehlen, Santhosh Sethuramanujam, Hidekiyo Harada, Vera L. Bonilha, Gautam Awatramani, Rod Bremner, Philippe P. Monnier

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Figure 6

Blocking neogenin promotes photoreceptor survival.

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Blocking neogenin promotes photoreceptor survival. (A) Timing of rod dea...
(A) Timing of rod death in the mouse models used. Arrows indicate timing of the initial treatment. Arrowheads indicate tissue harvest. (B–D) Representative DAPI images taken 400 μm from the optic nerve head (ONH). Scale bar: 20 μm. Dashed lines indicate ONL borders. (B) Rd1 retina injected with 4Ig (1 μg/μL) or PBS on P9 and P15 and harvested on P21. (C) Rd10 retina injected with 4Ig (1 μg/μL) or PBS on P20, P30, and P40 and harvested on P50. (D) RhoP23H/P23H retina injected with 4Ig (1 μg/μL) or PBS on P10 and harvested on P24. (E–G) Quantification of data from B and C. ONL size was measured in the nasal and temporal retina at 400 μm from the ONH and averaged. n = 8 and n = 6 for Rd1; n = 10 and n = 11 for Rd10; n = 8 and n = 6 for RhoP23H/P23H. **P < 0.01, ***P < 0.001. Statistical significance determined by Student’s t test. (H) Rd1 retina treated with PBS or 4Ig (1 μg/μL) as above and harvested on P30. Representative images stained for rods (Rhodopsin), cones (Cone Arrestin) and DAPI. Dashed lines indicate ONL borders. Scale bar: 10 μm. (I) Quantification of data from H demonstrating that 4Ig increased cone numbers. Measurements were made in nasal and temporal quadrants of the central retina and averaged. n = 7 for each; ****P < 0.0001. Significance determined by Student’s t test. (J and K) Rd1 retina injected on P9 and P15 with PBS, CNTF (0.8 μg/μL), 4Ig (0.5 μg/μL), or CNTF (0.8 μg/μL) + 4Ig (0.5 μg/μL) and harvested on P21. (J) Representative DAPI images of P21 Rd1 retina. Scale bar: 20 μm. Dashed lines indicate ONL borders. (K) Quantification of data from J. 4Ig (n = 8), CNTF (n = 7), and CNTF + 4Ig (n = 8) significantly increased the ONL thickness versus PBS (n = 8; ***P < 0.001). CNTF + 4Ig significantly increased thickness versus 4Ig or CNTF (†††P < 0.001). Significance determined by 1-way ANOVA followed by Bonferroni’s test.