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 2

cAMP promotes photoreceptor cell death through neogenin.

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cAMP promotes photoreceptor cell death through neogenin. (A) P9 C57BL/6J...
(A) P9 C57BL/6J (WT) mice received an intravitreal injection of 10 mM 8Br-cAMP, and eyes were harvested on P12. Intravitreal injection of 8Br-cAMP led to accumulation of neogenin in the soma of some photoreceptors (arrow), possibly related to initiation of cell death. Note: Gain settings were increased for this image. Scale bar: 20 μm. (B and C) P9 C57BL/6J (WT) mice received an intravitreal injection of 10 mM 8Br-cAMP, and eyes were harvested on P11. In situ hybridization was performed to assess neogenin mRNA levels. (C) Quantification of data from B. 8Br-cAMP led to a significant increase in neogenin mRNA levels in the IS/OS. n = 12 for each; ****P < 0.0001. Significance determined using Student’s t test. (D and E) P9 WT mice received an intravitreal injection of PBS, 10 mM 8Br-cAMP, or 10 mM 8Br-cAMP + 1 μg/μL 4Ig (a neogenin function–blocking peptide). Eyes were harvested on P12 and cryosectioned, and TUNEL staining was performed. (D) Representative TUNEL (red) images along with a nuclear stain (DAPI; blue) for each treatment group. Scale bars: 20 μm. (E) Quantification of data from D. 8Br-cAMP (n = 6) led to a significant increase in the number of TUNEL-positive cells in the ONL compared with PBS treatment (n = 4, **P < 0.01), which was prevented by coadministration of 4Ig (n = 4; *P < 0.05 compared with 8Br-cAMP). Significance determined using 1-way ANOVA followed by Šidák’s multiple-comparisons test.