A Zebrafish Model of Retinitis Pigmentosa Shows Continuous Degeneration and Regeneration of Rod Photoreceptors.

Abirami Santhanam,Eyad Shihabeddin,Joshua A Atkinson,Ya-Ping Lin,John O’Brien,Duc Nguyen

doi:10.3390/cells9102242

Abstract

More than 1.5 million people suffer from Retinitis Pigmentosa, with many experiencing partial to complete vision loss. Regenerative therapies offer some hope, but their development is challenged by the limited regenerative capacity of mammalian model systems. As a step toward investigating regenerative therapies, we developed a zebrafish model of Retinitis Pigmentosa that displays ongoing regeneration. We used Tol2 transgenesis to express mouse rhodopsin carrying the P23H mutation and an epitope tag in zebrafish rod photoreceptors. Adult and juvenile fish were examined by immunofluorescence, TUNEL and BrdU incorporation assays. P23H transgenic fish expressed the transgene in rods from 3 days post fertilization onward. Rods expressing the mutant rhodopsin formed very small or no outer segments and the mutant protein was delocalized over the entire cell. Adult fish displayed thinning of the outer nuclear layer (ONL) and loss of rod outer segments, but retained a single, sparse row of rods. Adult fish displayed ongoing apoptotic cell death in the ONL and an abundance of proliferating cells, predominantly in the ONL. There was a modest remodeling of bipolar and Müller glial cells. This transgenic fish will provide a useful model system to study rod photoreceptor regeneration and integration.

Highlights

Retinitis Pigmentosa (RP), a genetically-based retinal degenerative disease, causes the death of rod photoreceptors and progressive vision loss, leading to blindness in many patients [1,2]
At 3 dpf the P23H transgenic fish showed expression of the Flag-labeled mutant rhodopsin, co-labeled with the Retp1 anti-rhodopsin antibody in numerous cells spread throughout the outer nuclear layer (ONL) of the central retina (Figure 2D)
These cells did not co-label with the Zpr1 antibody that binds to double cone photoreceptors [33], which instead labeled numerous small structures reminiscent of nascent cone outer segments throughout the central retina (Figure 2N)

Summary

Introduction

Retinitis Pigmentosa (RP), a genetically-based retinal degenerative disease, causes the death of rod photoreceptors and progressive vision loss, leading to blindness in many patients [1,2]. RP primarily leads to rod photoreceptor cell death associated with night blindness and peripheral vision loss referred to as “tunnel vision,” followed by cone photoreceptor deterioration and loss of central vision. Different modes of inheritance have been reported, including autosomal recessive (arRP), dominant (adRP), and X-linked (xRP) genetic traits [5,6,7]. Rhodopsin mutations account for 30% of adRP cases among Americans of European origin. The P23H (Proline to Histidine) opsin mutation is the most common cause of adRP, accounting for ~10% of adRP cases in

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Conclusion