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Li S, Jin M. Ablation of Fatty Acid Transport Protein-4 Enhances Cone Survival, M-cone Vision, and Synthesis of Cone-Tropic 9- cis-Retinal in rd12 Mouse Model of Leber Congenital Amaurosis. J Neurosci 2024; 44:e1994232024. [PMID: 38811164 PMCID: PMC11223470 DOI: 10.1523/jneurosci.1994-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 12/03/2023] [Accepted: 05/22/2024] [Indexed: 05/31/2024] Open
Abstract
The canonical visual cycle employing RPE65 as the retinoid isomerase regenerates 11-cis-retinal to support both rod- and cone-mediated vision. Mutations of RPE65 are associated with Leber congenital amaurosis that results in rod and cone photoreceptor degeneration and vision loss of affected patients at an early age. Dark-reared Rpe65-/- mouse has been known to form isorhodopsin that employs 9-cis-retinal as the photosensitive chromophore. The mechanism regulating 9-cis-retinal synthesis and the role of the endogenous 9-cis-retinal in cone survival and function remain largely unknown. In this study, we found that ablation of fatty acid transport protein-4 (FATP4), a negative regulator of 11-cis-retinol synthesis catalyzed by RPE65, increased the formation of 9-cis-retinal, but not 11-cis-retinal, in a light-independent mechanism in both sexes of RPE65-null rd12 mice. Both rd12 and rd12;Fatp4-/- mice contained a massive amount of all-trans-retinyl esters in the eyes, exhibiting comparable scotopic vision and rod degeneration. However, expression levels of M- and S-opsins as well as numbers of M- and S-cones surviving in the superior retinas of rd12;Fatp4-/ - mice were at least twofold greater than those in age-matched rd12 mice. Moreover, FATP4 deficiency significantly shortened photopic b-wave implicit time, improved M-cone visual function, and substantially deaccelerated the progression of cone degeneration in rd12 mice, whereas FATP4 deficiency in mice with wild-type Rpe65 alleles neither induced 9-cis-retinal formation nor influenced cone survival and function. These results identify FATP4 as a new regulator of synthesis of 9-cis-retinal, which is a "cone-tropic" chromophore supporting cone survival and function in the retinas with defective RPE65.
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Affiliation(s)
- Songhua Li
- Neuroscience Center, Louisiana State University School of Medicine, LSU Health New Orleans, New Orleans, Louisiana 70112
| | - Minghao Jin
- Neuroscience Center, Louisiana State University School of Medicine, LSU Health New Orleans, New Orleans, Louisiana 70112
- Department of Ophthalmology, Louisiana State University School of Medicine, LSU Health New Orleans, New Orleans, Louisiana 70112
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Lu CF, Zhou YN, Zhang J, Su S, Liu Y, Peng GH, Zang W, Cao J. The role of epigenetic methylation/demethylation in the regulation of retinal photoreceptors. Front Cell Dev Biol 2023; 11:1149132. [PMID: 37305686 PMCID: PMC10251769 DOI: 10.3389/fcell.2023.1149132] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 05/09/2023] [Indexed: 06/13/2023] Open
Abstract
Photoreceptors are integral and crucial for the retina, as they convert light into electrical signals. Epigenetics plays a vital role in determining the precise expression of genetic information in space and time during the development and maturation of photoreceptors, cell differentiation, degeneration, death, and various pathological processes. Epigenetic regulation has three main manifestations: histone modification, DNA methylation, and RNA-based mechanisms, where methylation is involved in two regulatory mechanisms-histone methylation and DNA methylation. DNA methylation is the most studied form of epigenetic modification, while histone methylation is a relatively stable regulatory mechanism. Evidence suggests that normal methylation regulation is essential for the growth and development of photoreceptors and the maintenance of their functions, while abnormal methylation can lead to many pathological forms of photoreceptors. However, the role of methylation/demethylation in regulating retinal photoreceptors remains unclear. Therefore, this study aims to review the role of methylation/demethylation in regulating photoreceptors in various physiological and pathological situations and discuss the underlying mechanisms involved. Given the critical role of epigenetic regulation in gene expression and cellular differentiation, investigating the specific molecular mechanisms underlying these processes in photoreceptors may provide valuable insights into the pathogenesis of retinal diseases. Moreover, understanding these mechanisms could lead to the development of novel therapies that target the epigenetic machinery, thereby promoting the maintenance of retinal function throughout an individual's lifespan.
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Affiliation(s)
- Chao-Fan Lu
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Ya-Nan Zhou
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Jingjing Zhang
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Songxue Su
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Yupeng Liu
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Guang-Hua Peng
- Department of Pathophysiology, Basic Medical College, Zhengzhou University, Zhengzhou, China
- Laboratory of Visual Cell Differentiation and Regulation, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Weidong Zang
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
| | - Jing Cao
- Department of Anatomy, Basic Medical College, Zhengzhou University, Zhengzhou, China
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