Investigative Ophthalmology & Visual Science Cover Image for Volume 65, Issue 7
June 2024
Volume 65, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2024
Characterization of a double knockout mouse model of blue cone monochromacy
Author Affiliations & Notes
  • Mikayla Puska
    Neuroscience, University of Washington, Seattle, Washington, United States
  • Michelle Giarmarco
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • Jay Neitz
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • Maureen Neitz
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • James A Kuchenbecker
    Ophthalmology, University of Washington, Seattle, Washington, United States
  • Footnotes
    Commercial Relationships   Mikayla Puska None; Michelle Giarmarco None; Jay Neitz None; Maureen Neitz None; James Kuchenbecker None
  • Footnotes
    Support  NIH NEI P30EY001730, Research to Prevent Blindness
Investigative Ophthalmology & Visual Science June 2024, Vol.65, 4690. doi:
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      Mikayla Puska, Michelle Giarmarco, Jay Neitz, Maureen Neitz, James A Kuchenbecker; Characterization of a double knockout mouse model of blue cone monochromacy. Invest. Ophthalmol. Vis. Sci. 2024;65(7):4690.

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

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Abstract

Purpose : Mutations in genes encoding opsins are associated with varying degrees of colorblindness and retinal degeneration. Ma et al. (2022 Human Gene Therapy, 33, p708) generated a double cone opsin knockout mouse model of blue cone monochromacy (BCM) by mating an Opn1mw knockout to an Opn1sw knockout, both generated using gene traps. Unfortunately, the retinas of the animals degenerated showing a significant reduction of viable cones by 3 months, making the mice of limited use as a model of versions of BCM in which many cones remain viable. Additionally, no rod outer segments are formed in the mouse rhodopsin knockout model generated by targeted gene disruption reported by Lem et al. (1999, PNAS 96, p736), and over 90% of the rod photoreceptors degenerate after 90 days. Here, we report and characterize a new mouse line that lacks both blue (S) and green (M) sensitive cone opsins but maintains a viable cone population to one year old.

Methods : Double knockout (DKO) mice were created by Regeneron by fully deleting both genes using genome editing. The mice were euthanized and the eyes were embedded in OCT. 20µm cryosections were stained using immunohistochemistry. We used confocal microscopy to examine retinal morphology and markers for degeneration and compared DKO animals with a wild-type (WT) strain and a degeneration strain (AIPL1-/-) processed in the same way.

Results : The absence of both S and M cone opsin was confirmed in the knockout mice, and despite the lack of cone opsin expression, the mice were found to maintain a healthy population of opsin-less cones for at least one year. However, the DKO mice had approximately 30% fewer cones in their retinas at one year than WT mice. The populations of activated Muller glia cells, recruited macrophages, non-apoptotic dying cells, and microglia in the DKO retinas match those seen in the WT retinas and are significantly lower than the populations seen in the AIPL1-/- degeneration model. This suggests that the retina is not in an active state of degeneration for at least one year.

Conclusions : This model will be useful for the development of cone opsin gene therapies and can serve as a model for forms of BCM in which the expression of L and M opsin is lost but many cones remain viable. It also has implications for understanding the health of cones without the cone opsin in which many but not all cones remain viable and differs from the fate of rods without rhodopsin.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

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