June 2020
Volume 61, Issue 7
ARVO Annual Meeting Abstract  |   June 2020
Evaluation of a gene augmentation strategy for treating CRX-linked retinopathies
Author Affiliations & Notes
    Ophthalmology and Visual Sciences, Washington University in St. Louis, Saint Louis, Missouri, United States
  • Shiming Chen
    Ophthalmology and Visual Sciences, Washington University in St. Louis, Saint Louis, Missouri, United States
  • Footnotes
    Commercial Relationships   CHI SUN, None; Shiming Chen, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 2743. doi:
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      CHI SUN, Shiming Chen; Evaluation of a gene augmentation strategy for treating CRX-linked retinopathies. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2743.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose : The Cone-rod homeobox (CRX) is a transcription factor essential for photoreceptor function and survival. Mutations in human CRX cause incurable photoreceptor diseases. This research aimed to evaluate the therapeutic potential of CRX gene augmentation in a mouse model of Crx null mutations.

Methods : We created a new mouse line, Tet-On-hCRX, in which a transgene expresses FLAG-tagged human CRX driven by a tetracycline-responsive promoter. We have confirmed that this system expresses CRX in the presence of doxycycline (Dox). Tet-On-hCRX mice were crossed onto the Crx-/- background to determine if induced CRX expression can rescue defects in Crx-/- photoreceptors. Dox treatments were initiated at postnatal (P) day P7, P14, and P21. After 7 or 14 days of treatment, retinae from Dox-treated and control mice were analyzed by qRT-PCR for differential expression of CRX and the downstream target-gene Rhodopsin (Rho) and by H&E staining for morphological improvements.

Results : Induced CRX expression was detected in treated Crx-/- mutants at all ages during retinal development, confirming the success of the transgene system. Although minimal Rho expression was detected in non-treated Crx-/- mutants, Dox-treated mutants displayed significant upregulation of Rho expression, which positively correlated with induced CRX expression. Positive correlation was also found between Dox dose and expression of CRX and Rho for all treatment conditions. P21-35 induction resulted in a 5-fold increase in Rho expression, and result comparison of different treatment conditions suggested that early initiation (P7-21) is more effective in inducing Rho expression (64-fold). In addition, signs of improved photoreceptor survival were detected in treated mutants. Altogether, our results imply Crx-/- photoreceptors maintain a plastic window for therapeutic intervention.

Conclusions : CRX gene augmentation can be a potential strategy to treat photoreceptor diseases associated with CRX loss-of-function mutations. Future research will determine the essential time and levels of CRX expression required for the development of healthy and functional photoreceptors. The outcome will inform the development of AAV gene therapy for CRX-linked retinopathies.

This is a 2020 ARVO Annual Meeting abstract.


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