Department of Ophthalmology, The Louis J. Fox Center for Vision Restoration, Pittsburgh, Pennsylvania, United States of America.
Department of Developmental Biology, The McGowan Institute for Regenerative Medicine, The University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
PLoS Genet. 2021 Nov 4;17(11):e1009885. doi: 10.1371/journal.pgen.1009885. eCollection 2021 Nov.
Molecular insights into the selective vulnerability of retinal ganglion cells (RGCs) in optic neuropathies and after ocular trauma can lead to the development of novel therapeutic strategies aimed at preserving RGCs. However, little is known about what molecular contexts determine RGC susceptibility. In this study, we show the molecular mechanisms underlying the regional differential vulnerability of RGCs after optic nerve injury. We identified RGCs in the mouse peripheral ventrotemporal (VT) retina as the earliest population of RGCs susceptible to optic nerve injury. Mechanistically, the serotonin transporter (SERT) is upregulated on VT axons after injury. Utilizing SERT-deficient mice, loss of SERT attenuated VT RGC death and led to robust retinal axon regeneration. Integrin β3, a factor mediating SERT-induced functions in other systems, is also upregulated in RGCs and axons after injury, and loss of integrin β3 led to VT RGC protection and axon regeneration. Finally, RNA sequencing analyses revealed that loss of SERT significantly altered molecular signatures in the VT retina after optic nerve injury, including expression of the transmembrane protein, Gpnmb. GPNMB is rapidly downregulated in wild-type, but not SERT- or integrin β3-deficient VT RGCs after injury, and maintaining expression of GPNMB in RGCs via AAV2 viruses even after injury promoted VT RGC survival and axon regeneration. Taken together, our findings demonstrate that the SERT-integrin β3-GPNMB molecular axis mediates selective RGC vulnerability and axon regeneration after optic nerve injury.
对视网膜神经节细胞 (RGC) 在视神经病变和眼外伤后选择性易损性的分子见解，可以导致开发旨在保护 RGC 的新治疗策略。然而，对于哪些分子环境决定了 RGC 的易感性，人们知之甚少。在这项研究中，我们展示了视神经损伤后 RGC 区域性差异易损性的分子机制。我们确定了小鼠外周腹侧 (VT) 视网膜中的 RGC 是最早易受视神经损伤影响的 RGC 群体。从机制上讲，损伤后 5-羟色胺转运体 (SERT) 在 VT 轴突上上调。利用 SERT 缺陷型小鼠，SERT 的缺失减轻了 VT RGC 的死亡，并导致强烈的视网膜轴突再生。整合素 β3 是介导 SERT 在其他系统中诱导功能的一个因素，它在损伤后 RGC 和轴突中也上调，而整合素 β3 的缺失导致了 VT RGC 的保护和轴突再生。最后，RNA 测序分析表明，SERT 的缺失显著改变了视神经损伤后 VT 视网膜中的分子特征，包括跨膜蛋白 Gpnmb 的表达。Gpnmb 在野生型中迅速下调，但在损伤后的 SERT 或整合素 β3 缺陷型 VT RGC 中没有下调，通过 AAV2 病毒即使在损伤后保持 GPNMB 在 RGC 中的表达，也促进了 VT RGC 的存活和轴突再生。总之，我们的研究结果表明，SERT-整合素 β3-GPNMB 分子轴介导了视神经损伤后选择性 RGC 易损性和轴突再生。
