Dvoriantchikova Galina, Moulin Chloe, Fleishaker Michelle, Almeida Vania, Pelaez Daniel, Lam Byron L, Ivanov Dmitry
Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, FL 33136.
The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, FL 33136.
Proc Natl Acad Sci U S A. 2025 Mar 11;122(10):e2420091122. doi: 10.1073/pnas.2420091122. Epub 2025 Mar 7.
The retina is responsible for converting light into electrical signals that, when transmitted to the brain, create the sensation of vision. The mammalian retina is epigenetically unique since the differentiation of retinal progenitor cells (RPCs) into retinal cells is accompanied by a decrease in DNA methylation in the promoters of many genes important for retinal development and function. However, the pathway responsible for DNA demethylation and its role in retinal development and function were unknown. We hypothesized that the Ten-Eleven Translocation (TET) family of dioxygenases plays a key role in this pathway. To this end, we knocked out the TET family in RPCs and characterized the TET-deficient and control retinas using various approaches including electron microscopy, electroretinogram tests, TUNEL, RNA-seq, WGBS, and 5hmC-Seal. We found that while the TET-dependent DNA demethylation pathway contributes to the development of many retinal cell types, it is the most significant contributor to rod and cone photoreceptor development and function. We found that genetic ablation of TET enzymes in RPCs prevents demethylation and the activity of genes essential for rod specification and for rod and cone maturation. Reduced activity of genes responsible for rod specification results in the TET-deficient retina being depleted of these neurons. Meanwhile, reduced activity of genes responsible for rod and cone maturation leads to the underdevelopment or complete absence of outer segments and synaptic termini in the TET-deficient photoreceptors, which results in loss of their function and leads to blindness. These function-deprived, underdeveloped photoreceptors die over time, leading to retinal dystrophy.
视网膜负责将光转化为电信号，当这些信号传输到大脑时，便产生视觉。哺乳动物的视网膜在表观遗传上具有独特性，因为视网膜祖细胞（RPCs）向视网膜细胞的分化伴随着许多对视网膜发育和功能至关重要的基因启动子中DNA甲基化的减少。然而，负责DNA去甲基化的途径及其在视网膜发育和功能中的作用尚不清楚。我们推测双加氧酶的十一易位（TET）家族在该途径中起关键作用。为此，我们在RPCs中敲除了TET家族，并使用包括电子显微镜、视网膜电图测试、TUNEL、RNA测序、全基因组亚硫酸氢盐测序（WGBS）和5-羟甲基胞嘧啶测序（5hmC-Seal）等各种方法对TET缺陷型和对照视网膜进行了表征。我们发现，虽然依赖TET的DNA去甲基化途径有助于多种视网膜细胞类型的发育，但它对视杆和视锥光感受器的发育和功能贡献最为显著。我们发现，RPCs中TET酶的基因缺失会阻止去甲基化以及视杆特异性和视杆与视锥成熟所必需的基因的活性。负责视杆特异性的基因活性降低导致TET缺陷型视网膜中这些神经元的缺失。同时，负责视杆和视锥成熟的基因活性降低导致TET缺陷型光感受器中外段和突触末端发育不全或完全缺失，这导致它们的功能丧失并导致失明。这些功能缺失、发育不全的光感受器会随着时间的推移而死亡，导致视网膜营养不良。
