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 3

Elevated neogenin expression in Rd1 and Rd10 photoreceptors.

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Elevated neogenin expression in Rd1 and Rd10 photoreceptors. (A) Represe...
(A) Representative images of cryosectioned C57BL/6J (WT) retina, and Rd1 or Rd10 retina immunostained for neogenin (red) on P12, P16, or P30. Dashed lines indicate border of the IS/OS. Scale bars: 30 μm. All images were taken under identical conditions/settings. (B) Quantification of data from A. Neogenin intensity levels were significantly increased in the IS/OS of P12/P16 Rd1 and P30 Rd10 when compared with WT mice of the same age. P12: n = 4 and n = 5; P16 n = 4 and n = 5; P30 n = 6 and n = 4. **P < 0.01, ***P < 0.001. Significance determined by Student’s t test. (C) Representative image of a P12 Rd1 ONL demonstrating coexpression of neogenin (green) and cleaved caspase-3 (red) in the same cell (white arrows). Nuclear stain appears in blue (DAPI). Scale bar: 20 μm. (D–F) PKA inhibitor KT5720 suppresses neogenin expression in Rd1 retinal photoreceptor segments. P12 Rd1 mice received an intravitreal injection of either 4 mM KT5720 or PBS and were harvested on P13 for analysis. (D) Real-time PCR of intron 1, intron 2, and the last exon of neogenin from the indicated treatments (n = 3; *P < 0.05). Significance determined by Student’s t test. (E) Nuclear (DAPI, blue) and neogenin (green) staining of retinal sections from the indicated treatments. Scale bar: 50 μm. White arrows indicate neogenin in IS/OS. OPL, outer plexiform layer. (F) Quantification of data from E. Significance determined by Student’s t test (n = 4 for each; *P < 0.05).