Prcd KO manuscript source data

Progressive Rod-Cone Degeneration (PRCD) is an integral membrane protein found in photoreceptor outer segment (OS) disc membranes and its function remains unknown. Mutations in Prcd are implicated in Retinitis pigmentosa (RP) in humans and multiple dog breeds. PRCD-deficient models exhibit decreased levels of cholesterol in the plasma. However, potential changes in the retinal cholesterol remain unexplored. In addition, impaired phagocytosis observed in these animal models points to potential deficits in the retinal pigment epithelium (RPE). Here, using a Prcd-/- murine model we investigated the alterations in the retinal cholesterol levels and impairments in the structural and functional integrity of the RPE. Lipidomic and immunohistochemical analyses show a 5-fold increase in the levels of cholesteryl esters (C.Es) and lipid deposits in the PRCD-deficient retina, respectively, indicating alterations in total retinal cholesterol. Furthermore, the RPE of Prcd-/- mice exhibit a 1.7-fold increase in the expression of lipid transporter gene ATP-binding cassette transporter A1 (Abca1). Longitudinal fundus and spectral domain optical coherence tomography (SD-OCT) examinations showed focal lesions and RPE hyperreflectivity. Strikingly, the RPE of Prcd-/- mice exhibited age-related pathological features such as lipofuscin accumulation, Bruch’s membrane (BrM) deposits and drusenoid focal deposits, mirroring an Age-related Macular Degeneration (AMD)-like phenotype. We propose that the extensive lipofuscin accumulation likely impairs lysosomal function, leading to the defective phagocytosis observed in Prcd-/- mice. Our findings support the dysregulation of retinal cholesterol homeostasis in the absence of PRCD. Further, we demonstrate that progressive photoreceptor degeneration in Prcd-/- mice is accompanied by progressive structural and functional deficits in the RPE, which likely exacerbates vision loss over time.

进行性杆锥变性蛋白（Progressive Rod-Cone Degeneration, PRCD）是一种定位于光感受器外节盘膜的整合膜蛋白，其具体功能迄今仍未明确。PRCD基因的突变与人类及多个犬品种的色素性视网膜炎（Retinitis pigmentosa, RP）密切相关。PRCD缺陷模型的血浆胆固醇水平显著降低，但视网膜胆固醇的潜在变化尚未得到探索。此外，在这些动物模型中观察到的吞噬功能受损，提示视网膜色素上皮（retinal pigment epithelium, RPE）可能存在功能缺陷。本研究利用Prcd基因敲除（Prcd-/-）小鼠模型，系统探究了视网膜胆固醇水平的改变以及RPE结构与功能完整性的损伤情况。脂质组学与免疫组织化学分析显示，PRCD缺陷型视网膜的胆固醇酯（cholesteryl esters, C.Es）水平升高5倍，同时出现脂质沉积，表明视网膜总胆固醇稳态发生异常改变。此外，Prcd-/-小鼠的RPE中脂质转运基因ATP结合盒转运蛋白A1（ATP-binding cassette transporter A1, ABCA1）的表达上调1.7倍。纵向眼底检查与光谱域光学相干断层扫描（spectral domain optical coherence tomography, SD-OCT）结果显示，模型小鼠出现局灶性病变与RPE高反射性表现。值得注意的是，Prcd-/-小鼠的RPE呈现出典型的年龄相关性病理特征，包括脂褐素沉积、布鲁赫膜（Bruch’s membrane, BrM）沉积以及玻璃膜疣样局灶性沉积，模拟出年龄相关性黄斑变性（Age-related Macular Degeneration, AMD）样表型。我们推测，大量脂褐素的沉积可能损伤溶酶体功能，进而导致Prcd-/-小鼠出现吞噬功能缺陷。本研究结果证实，PRCD缺失会导致视网膜胆固醇稳态失调。此外，本研究证实Prcd-/-小鼠的进行性光感受器变性伴随RPE的进行性结构与功能缺陷，该缺陷可能随时间推移进一步加重视力丧失。