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Abigail Ruth Hayes, Ratnesh Singh, Visvanathan Ramamurthy; ARL2BP is essential for the function of rod and cone photoreceptor cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified.
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© ARVO (1962-2015); The Authors (2016-present)
Blinding diseases such as retinitis pigmentosa (RP) are linked to defects in multiple ciliary proteins, including ARL2BP, a protein thought to be involved in ciliogenesis. Despite the link between defective ciliogenesis and blindness, little is known about the mechanisms that control photoreceptor cilia growth and maintenance. Using an animal model lacking ARL2BP, our goal is to identify the role of ARL2BP in the development and function of photoreceptors.
In this study, we generated a global knockout (KO) of ARL2BP in mice using the Crispr-Cas9 system. Protein and mRNA levels were measured by immunoblotting and real-time PCR. Immunocytochemical staining was used to investigate the morphology of the retina and protein localization in photoreceptor cells. Electroretinogram (ERG) recordings were performed to assess photoreceptor function. Littermates were used in all experiments as controls (n=4).
At 3 weeks of age, ERGs revealed a significant reduction in scotopic and photopic responses in animals lacking ARL2BP (↓50%), while heterozygous littermates were similar in response to wild type (WT) mice. Immunocytochemical staining of retinal sections from adult KO animals showed a degeneration of photoreceptor nuclei compared to WT littermates (↓40%). Despite a reduction in expression of photoreceptor outer segment proteins, such as rhodopsin, G-protein transducin, and phosphodiesterase 6, their localization was unaffected.
Knockout of ARL2BP produced a defect in rod and cone function phenocopying the patient mutations. Our preliminary results suggest that ARL2BP is involved in the development of photoreceptor outer segments, but not in protein trafficking. Our current efforts are focused on understanding the role of ARL2BP and its interacting partners to help delineate the mechanism underlying photoreceptor outer segment biogenesis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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