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 1

cAMP induces neogenin expression in the retina.

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cAMP induces neogenin expression in the retina. (A and B) Retinoblastoma...
(A and B) Retinoblastoma (Y79) cells were cultured with or without 0.5 mM 8-Br-cAMP (cAMP) or 0.5 mM 8-Br-cGMP (cGMP) for 48 hours. (A) Western blot of neogenin from Y79 whole cell lysates following the indicated treatment. Ctrl, Control. (B) Quantification of data from A, normalized to GAPDH (n = 3 for each; *P < 0.05, **P < 0.01). Significance determined by 1-way ANOVA followed by Šidák’s multiple-comparisons test. (C–E) P9 C57BL/6J (WT) mice received 1 intravitreal injection of either 10 mM 8Br-cAMP or PBS. Eyes were harvested on P12 and cryosectioned. (C) Representative images of P12 retina treated with PBS or 10 mM 8Br-cAMP and stained for neogenin (red), rhodopsin (green), and nuclei (DAPI; blue). Arrows indicate inner/outer segments of photoreceptors. IPL, inner plexiform layer. Scale bars: 20 μm. (D) Higher-magnification images of P12 retina treated with PBS or 8Br-cAMP stained for neogenin (red), with the dashed lines indicating the border of the inner/outer segments (IS/OS). Note the characteristic punctate appearance of neogenin staining. Scale bar: 20 μm. (E) Quantification of data from D. Neogenin signal in the IS/OS was significantly elevated following 8Br-cAMP intravitreal injection (n = 4 for each; *P < 0.05). Significance determined by Student’s t test.