Retinal degeneration slow (RDS) is a photoreceptor-specific glycoprotein critical for rod and cone outer segment (OS) rim formation and maintenance. Rim formation is critical for OS structure; in the absence of RDS no rod OSs are formed and no rod function is detected while cones develop dysmorphic balloon-like OSs that lack lamellae but contain cone opsins and retain ~50% of function. Developing a thorough understanding of the role and function of RDS in rods and cones is critical as over 100 different mutations in RDS cause retinal degenerative diseases with widely varying phenotypes including rod-dominant autosomal dominant retinitis pigmentosa (ADRP) and multiple classes of cone-dominant macular dystrophy (MD). Studies have suggested that mutations that cause rod-dominant disease result in null alleles likely due to protein misfolding while mutations that cause cone-dominant disease have a more complex pathology. Assessment of disease in patients has shown that in many cases, RDS-associated macular vision loss is not only associated with primary defects in photoreceptors, but with subsequent secondary toxicity and changes in the retinal pigment epithelium (RPE) and choroidal/retinal vasculature. Nothing is known about the link between these primary defects and the blinding secondary sequellae; however, for the first time we have generated mouse models which facilitate study of this issue. The diversity in RDS-associated phenotypes seen in patients coupled with data from cone and rod- dominant mouse models suggests that rods and cones have different requirements for RDS. It is not clear why these two cell types should be so differently affected by different mutations, primarily because our current knowledge of the precise function of RDS in these two cell types is incomplete. Here we plan to focus our investigation on understanding how RDS functions differently in rods and cones with particular interest in RDS initial complex formation and trafficking, role in cone vs. rod OS structures, and effects of RDS mutations on overall retinal health. We will conduct a careful assessment of the molecular properties of RDS and RDS mutants, with specific regard to complex assembly in the IS and trafficking to the OS in Aim 1; and study the role of RDS in OS structures, disc/rim formation, and disc sizing in Aim 2. Of particular interest will be differences in these processes between rods and cones. Links between RDS-mutation-associated photoreceptor defects and alterations in the RPE and choroid will be assessed in Aim 3. We have a set of unique tools at our disposal and advanced genetically engineered mouse models to study how mutations in RDS result in diverse retinal pathologies as a consequence of abnormal OS formation and the role of RDS in the closed rim structure in rods and the open rim structures in cones. Given the lack of effective treatments for RDS-associated disease these studies are essential.

Public Health Relevance

The RDS-associated disease phenotypes are complex and multifactorial, involving not just photoreceptors, as has historically been reasoned, but also secondary effects on RPE cells and the retinal/choroidal vasculature. Understanding the mechanisms by which these complicated disease phenotypes develop is absolutely critical both for the development of treatments for RDS-associated disease and for our understanding of disease mechanisms associated with other genes in which the primary defect is in photoreceptors but the disease phenotype affects multiple tissues. Studies proposed in this application directly address these issues in unique ways that are novel and highly suited to our expertise and tools.

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
Project #
Application #
Study Section
Biology of the Visual System Study Section (BVS)
Program Officer
Neuhold, Lisa
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Houston
Engineering (All Types)
Biomed Engr/Col Engr/Engr Sta
United States
Zip Code
Agbaga, Martin-Paul; Merriman, Dana K; Brush, Richard S et al. (2018) Differential composition of DHA and very-long-chain PUFAs in rod and cone photoreceptors. J Lipid Res 59:1586-1596
Kelley, Ryan A; Al-Ubaidi, Muayyad R; Naash, Muna I (2018) Retbindin Is Capable of Protecting Photoreceptors from Flavin-Sensitized Light-Mediated Cell Death In Vitro. Adv Exp Med Biol 1074:485-490
LaVail, Matthew M; Nishikawa, Shimpei; Steinberg, Roy H et al. (2018) Phenotypic characterization of P23H and S334ter rhodopsin transgenic rat models of inherited retinal degeneration. Exp Eye Res 167:56-90
Ikelle, Larissa; Naash, Muna I; Al-Ubaidi, Muayyad R (2018) Role of Fibulins 2 and 5 in Retinal Development and Maintenance. Adv Exp Med Biol 1074:275-280
Zulliger, Rahel; Conley, Shannon M; Mwoyosvi, Maggie L et al. (2018) Oligomerization of Prph2 and Rom1 is essential for photoreceptor outer segment formation. Hum Mol Genet 27:3507-3518
Sinha, Tirthankar; Makia, Mustafa; Du, Jianhai et al. (2018) Flavin homeostasis in the mouse retina during aging and degeneration. J Nutr Biochem 62:123-133
Conley, Shannon M; Stuck, Michael W; Watson, Jamie N et al. (2017) Rom1 converts Y141C-Prph2-associated pattern dystrophy to retinitis pigmentosa. Hum Mol Genet 26:509-518
Kelley, Ryan A; Al-Ubaidi, Muayyad R; Sinha, Tirthankar et al. (2017) Ablation of the riboflavin-binding protein retbindin reduces flavin levels and leads to progressive and dose-dependent degeneration of rods and cones. J Biol Chem 292:21023-21034
Stuck, Michael W; Conley, Shannon M; Naash, Muna I (2016) PRPH2/RDS and ROM-1: Historical context, current views and future considerations. Prog Retin Eye Res 52:47-63
Kelley, Ryan A; Al-Ubaidi, Muayyad R; Naash, Muna I (2016) The Potential Role of Flavins and Retbindin in Retinal Function and Homeostasis. Adv Exp Med Biol 854:643-8

Showing the most recent 10 out of 71 publications