Department of Human Genetics, McGill University, Research Institute of the McGill University Health Centre, 1001 Decarie Boulevard, Montreal, Quebec, H4A 3J1, Canada.
Department of Ophthalmology, McGill University, 1001 Decarie Boulevard, Montreal, Quebec, H4A 3J1, Canada.
Exp Eye Res. 2019 Sep;186:107713. doi: 10.1016/j.exer.2019.107713. Epub 2019 Jun 27.
Zellweger Spectrum Disorder (ZSD) is an autosomal recessive disease caused by mutations in any one of 13 PEX genes whose protein products are required for peroxisome assembly. Retinopathy leading to blindness is one of the major untreatable handicaps faced by patients with ZSD but is not well characterized, and the requirement for peroxisomes in retinal health is unknown. To address this, we examined the progression of retinopathy from 2 to 32 weeks of age in our murine model for the common human PEX1-p.Gly843Asp allele (PEX1-p.Gly844Asp) using electrophysiology, histology, immunohistochemistry, electron microscopy, biochemistry, and visual function tests. We found that retinopathy in male and female PEX1-G844D mice was marked by an attenuated cone function and abnormal cone morphology early in life, with gradually decreasing rod function. Structural defects at the inner retina occurred later in the form of bipolar cell degradation (between 13 and 32 weeks). Inner segment disorganization and enlarged mitochondria were seen at 32 weeks, while other inner retinal cells appeared preserved. Visual acuity was diminished by 11 weeks of age, while signal transmission from the retina to the brain was relatively intact from 7 to 32 weeks of age. Molecular analyses showed that PEX1-G844D is a subfunctional but stable protein, contrary to human PEX1-G843D. Finally, C26:0 lysophosphatidylcholine was elevated in the PEX1-G844D retina, while phopshoethanolamine plasmalogen lipids were present at normal levels. These characterization studies identify therapeutic endpoints for future preclinical trials, including improving or preserving the electroretinogram response, improving visual acuity, and/or preventing loss of bipolar cells.
Zellweger 谱系障碍 (ZSD) 是一种常染色体隐性疾病,由 13 个 PEX 基因中的任何一个基因突变引起,这些基因的蛋白产物是过氧化物酶体组装所必需的。导致失明的视网膜病变是 ZSD 患者面临的主要无法治疗的障碍之一,但尚未得到很好的描述,过氧化物酶体在视网膜健康中的作用尚不清楚。为了解决这个问题,我们使用电生理学、组织学、免疫组织化学、电子显微镜、生物化学和视觉功能测试,研究了我们的常见人类 PEX1-p.Gly843Asp 等位基因(PEX1-p.Gly844Asp)的小鼠模型中从 2 到 32 周龄的视网膜病变进展。我们发现,PEX1-G844D 雄性和雌性小鼠的视网膜病变表现为早期锥细胞功能减弱和形态异常,随后杆细胞功能逐渐下降。在生命后期,以内节退化的形式出现结构缺陷(13 至 32 周)。32 周时可见内节组织紊乱和线粒体增大,而其他内节细胞似乎保存完好。11 周龄时视力下降,7 至 32 周时视网膜至大脑的信号传递相对完整。分子分析表明,PEX1-G844D 是一种功能减弱但稳定的蛋白,与人类 PEX1-G843D 相反。最后,PEX1-G844D 视网膜中的 C26:0 溶血磷脂酰胆碱升高,而磷酯酰乙醇胺质体脂质含量正常。这些特征研究确定了未来临床前试验的治疗终点,包括改善或维持视网膜电图反应、提高视力和/或防止双极细胞丢失。