Sequence variants in LOXL1 coding for the secreted enzyme lysyl oxidase homolog 1 (LOXL1) associate with pseudoexfoliation (PEX) syndrome, a condition that is characterized by the deposition of extracellular fibrillar PEX material in the anterior eye and other parts of the body. Since the specific role of LOXL1 in the pathogenesis of PEX is unclear, and an increase in its expression was reported for early stages of PEX syndrome, we generated and studied transgenic mice with ocular overexpression of its mouse ortholog Loxl1. The chicken βB1-crystallin promoter was used to overexpress Loxl1 in the lenses of βB1-crystallin-Loxl1 transgenic mice. Transgenic lenses contained high levels of the protein LOXL1 and its mRNA, which were both not detectable in lenses of wildtype littermates. In wildtype mice, immunoreactivity for LOXL1 was mainly seen extracellularly in region of the ciliary zonules. βB1-crystallin-Loxl1 littermates showed an additional diffuse immunostaining in lens fibers and capsule, and in the inner limiting membrane and retina indicating secretion of soluble LOXL1 from transgenic lenses. In addition, lens fibers of transgenic animals contained multiple distinct spots of very intense LOXL1 immunoreactivity. By transmission electron microscopy, those spots correlated with electron-dense round or oval bodies of 20–50 nm in diameter which were localized in the rough endoplasmic reticulum and not seen in wildtype lenses. Immunogold electron microscopy confirmed that the electron-dense bodies contained LOXL1 indicating aggregation of insoluble LOXL1. Similar structures were seen in the extracellular lens capsule suggesting their secretion from lens fibers. Otherwise, no changes were seen between the eyes of βB1-crystallin-Loxl1 mice and their wildtype littermates, neither by light microscopy and funduscopy of whole eyes, nor by scanning and quantitative transmission electron microscopy of ciliary epithelium and zonules. At one month of age, intraocular pressure was significantly higher in transgenic mice than in wildtype littermates. No differences in IOP were seen though at 2–5 months of age. We conclude that LOXL1 has a strong tendency to aggregate in the rER when expressed in vivo at high amounts. A similar scenario, involving intracellular aggregation of LOXL1 and secretion of LOXL1 aggregates into the extracellular space, may be involved in the early pathogenetic events in eyes of PEX patients.

LOXL1中编码分泌的赖氨酰氧化酶同源物1（LOXL1）的序列变异与假性剥脱（PEX）综合征相关，这种症状的特征是细胞外纤维PEX物质沉积在前眼和身体其他部位。由于LOXL1在PEX发病机理中的具体作用尚不清楚，并且据报道在PEX综合征的早期阶段其表达有所增加，因此我们生成并研究了其小鼠直系同源物Loxl1的眼过表达的转基因小鼠。鸡βB1-crystallin启动子被用来过量表达Loxl1在βB1-crystallin-Loxl1转基因小鼠的晶状体中。转基因晶状体含有高水平的蛋白质LOXL1及其mRNA，在野生型同窝幼虫的晶状体中均无法检测到。在野生型小鼠中，LOXL1的免疫反应性主要出现在睫状小带的细胞外。βB1-crystallin-Loxl1同窝幼仔在晶状体纤维和囊膜以及内界膜和视网膜中显示出额外的弥漫性免疫染色，表明转基因晶状体分泌了可溶性LOXL1。此外，转基因动物的晶状体纤维含有多个非常强烈的LOXL1免疫反应性的不同斑点。通过透射电子显微镜，这些斑点与直径为20–50 nm的电子致密圆形或椭圆形体相关，它们位于粗糙的内质网中，而在野生型晶状体中则看不到。免疫金电子显微镜证实，电子致密体含有LOXL1，表明不溶性LOXL1聚集。在细胞外晶状体囊中观察到相似的结构，表明它们是从晶状体纤维中分泌的。否则，通过全眼的光学显微镜和眼底镜检查，或者通过睫毛上皮和小带的扫描和定量透射电子显微镜，在βB1-crystallin-Loxl1小鼠的眼睛和它们的野生型同窝小鼠之间没有看到任何变化。在一个月大的时候，转基因小鼠的眼内压明显高于野生型同窝小鼠。尽管在2至5个月大时，眼压没有差异。我们得出结论，当表达时，LOXL1有很强的聚集在rER中的趋势 在细胞外晶状体囊中观察到相似的结构，表明它们是从晶状体纤维中分泌的。否则，通过全眼的光学显微镜和眼底镜检查，或者通过睫毛上皮和小带的扫描和定量透射电子显微镜，在βB1-crystallin-Loxl1小鼠的眼睛和它们的野生型同窝小鼠之间没有看到任何变化。在一个月大的时候，转基因小鼠的眼内压明显高于野生型同窝小鼠。尽管在2至5个月大时，眼压没有差异。我们得出结论，当表达时，LOXL1有很强的聚集在rER中的趋势 在细胞外晶状体囊中观察到相似的结构，表明它们是从晶状体纤维中分泌的。否则，通过全眼的光学显微镜和眼底镜检查，或者通过睫毛上皮和小带的扫描和定量透射电子显微镜，在βB1-crystallin-Loxl1小鼠的眼睛和它们的野生型同窝小鼠之间没有看到任何变化。在一个月大的时候，转基因小鼠的眼内压明显高于野生型同窝小鼠。尽管在2-5个月大时，眼压没有差异。我们得出结论，当表达时，LOXL1有很强的聚集在rER中的趋势 也不能通过扫描和定量透射电镜观察睫状上皮和小带。在一个月大的时候，转基因小鼠的眼内压明显高于野生型同窝小鼠。尽管在2至5个月大时，眼压没有差异。我们得出结论，当表达时，LOXL1有很强的聚集在rER中的趋势 也不能通过扫描和定量透射电镜观察睫状上皮和小带。在一个月大的时候，转基因小鼠的眼内压明显高于野生型同窝小鼠。尽管在2至5个月大时，眼压没有差异。我们得出结论，当表达时，LOXL1有很强的聚集在rER中的趋势体内大量存在。涉及LOXL1的细胞内聚集和LOXL1聚集物分泌到细胞外空间的类似情况可能与PEX患者眼中的早期致病事件有关。