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Xu P, Chen Z, Ma J, Shan Y, Wang Y, Xie B, Zheng D, Guo F, Song X, Gao G, Ye K, Liu Y, Pan G, Jiang B, Peng F, Zhong X. Biallelic CLCN2 mutations cause retinal degeneration by impairing retinal pigment epithelium phagocytosis and chloride channel function. Hum Genet 2023; 142:577-593. [PMID: 36964785 DOI: 10.1007/s00439-023-02531-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 02/06/2023] [Indexed: 03/26/2023]
Abstract
CLCN2 encodes a two-pore homodimeric chloride channel protein (CLC-2) that is widely expressed in human tissues. The association between Clcn2 and the retina is well-established in mice, as loss-of-function of CLC-2 can cause retinopathy in mice; however, the ocular phenotypes caused by CLCN2 mutations in humans and the underlying mechanisms remain unclear. The present study aimed to define the ocular features and reveal the pathogenic mechanisms of CLCN2 variants associated with retinal degeneration in humans using an in vitro overexpression system, as well as patient-induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) cells and retinal organoids (ROs). A patient carrying the homozygous c.2257C > T (p.R753X) nonsense CLCN2 mutation was followed up for > 6 years. Ocular features were comprehensively characterized with multimodality imaging and functional examination. The patient presented with severe bilateral retinal degeneration with loss of photoreceptor and RPE. In vitro, mutant CLC-2 maintained the correct subcellular localization, but with reduced channel function compared to wild-type CLC-2 in HEK293T cells. Additionally, patient iPSC-derived RPE cells carrying the CLCN2 mutation exhibited dysfunctional ClC-2 chloride channels and outer segment phagocytosis. Notably, these functions were rescued following the repair of the CLCN2 mutation using the CRISPR-Cas9 system. However, this variant did not cause significant photoreceptor degeneration in patient-derived ROs, indicating that dysfunctional RPE is likely the primary cause of biallelic CLCN2 variant-mediated retinopathy. This study is the first to establish the confirmatory ocular features of human CLCN2-related retinal degeneration, and reveal a pathogenic mechanism associated with biallelic CLCN2 variants, providing new insights into the cause of inherited retinal dystrophies.
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Affiliation(s)
- Ping Xu
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Zhuolin Chen
- Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, China
| | - Jianchi Ma
- Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Yongli Shan
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, South China, Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, 510530, China
| | - Yuan Wang
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Bingbing Xie
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Dandan Zheng
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Fuying Guo
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Xiaojing Song
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Guanjie Gao
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Ke Ye
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Yizhi Liu
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China
| | - Guangjin Pan
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, South China, Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, 510530, China
| | - Bin Jiang
- Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Fuhua Peng
- Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, China.
| | - Xiufeng Zhong
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, 510060, China.
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