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    xf2019@stanford.edu
    Department: Ophthalmology Research/Clinical Trials Position: Basic Life Research Scientist

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  • Mail Code: 5353

All Publications

  • GPX4 Promotes Optic Nerve Regeneration and RGC Neuroprotection. bioRxiv : the preprint server for biology Yang, M., Bian, F., Feng, X., Li, L., Huang, H., Liu, L., Dalal, R., Yang, H., Suraparaju, P. V., Cao, F., Ong, P., Luo, A., Liu, D., Hu, Y. 2025

    Abstract

    Preventing retinal ganglion cells (RGCs)'s soma and axon degeneration and promoting optic nerve (ON) regeneration holds great promise for effective glaucoma treatment. To explore potential neural repair strategies, we focused on glutathione peroxidase 4 (GPX4), a key regulator of lipid peroxidation. GPX4 is upregulated in surviving RGCs after acute ON crush or chronic ocular hypertension insult, and also in regenerating RGCs. AAV-mediated RGC-specific overexpression of GPX4 promotes significant ON regeneration and RGC survival, along with visual functional preservation, demonstrating the detrimental role of lipid peroxidation in glaucoma and the therapeutic potential of modulating lipid peroxidation through GPX4 in optic neuropathies.

    View details for DOI 10.1101/2025.06.03.657677

    View details for PubMedID 40501672

  • Optineurin-facilitated axonal mitochondria delivery promotes neuroprotection and axon regeneration. Nature communications Liu, D., Webber, H. C., Bian, F., Xu, Y., Prakash, M., Feng, X., Yang, M., Yang, H., You, I. J., Li, L., Liu, L., Liu, P., Huang, H., Chang, C. Y., Liu, L., Shah, S. H., La Torre, A., Welsbie, D. S., Sun, Y., Duan, X., Goldberg, J. L., Braun, M., Lansky, Z., Hu, Y. 2025; 16 (1): 1789

    Abstract

    Optineurin (OPTN) mutations are linked to amyotrophic lateral sclerosis (ALS) and normal tension glaucoma (NTG), but a relevant animal model is lacking, and the molecular mechanisms underlying neurodegeneration are unknown. We find that OPTN C-terminus truncation (OPTN∆C) causes late-onset neurodegeneration of retinal ganglion cells (RGCs), optic nerve (ON), and spinal cord motor neurons, preceded by a decrease of axonal mitochondria in mice. We discover that OPTN directly interacts with both microtubules and the mitochondrial transport complex TRAK1/KIF5B, stabilizing them for proper anterograde axonal mitochondrial transport, in a C-terminus dependent manner. Furthermore, overexpressing OPTN/TRAK1/KIF5B prevents not only OPTN truncation-induced, but also ocular hypertension-induced neurodegeneration, and promotes robust ON regeneration. Therefore, in addition to generating animal models for NTG and ALS, our results establish OPTN as a facilitator of the microtubule-dependent mitochondrial transport necessary for adequate axonal mitochondria delivery, and its loss as the likely molecular mechanism of neurodegeneration.

    View details for DOI 10.1038/s41467-025-57135-8

    View details for PubMedID 39979261

    View details for PubMedCentralID 3714538

  • A novel function of optineurin in axonal mitochondria transport for axon integrity and regeneration Hu, Y., Liu, D., Webber, H., Bian, F., Prakash, M., Li, L., You, I., Feng, X., Yang, H., Liu, L., Liu, P., Yang, M., Huang, H., Lansky, Z. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

    View details for Web of Science ID 001312227702281

  • Nme2Cas9-mediated <i>Pten</i> knockdown in RGCs promotes potent optic nerve regeneration after crush injury Bian, F., Feng, X., Li, L., Liu, L., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

    View details for Web of Science ID 001313316207287

  • Anti-lipid peroxidation promotes significant optic nerve regeneration and neuroprotection in mouse glaucoma models Yang, M., Li, L., Feng, X., Huang, H., Liu, L., Liu, D., Bian, F., Dalal, R., Yang, H., Cao, F., Ong, P., Luo, A., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2024

    View details for Web of Science ID 001313316200024

  • Optineurin-facilitated axonal mitochondria delivery promotes neuroprotection and axon regeneration. bioRxiv : the preprint server for biology Liu, D., Webber, H. C., Bian, F., Xu, Y., Prakash, M., Feng, X., Yang, M., Yang, H., You, I., Li, L., Liu, L., Liu, P., Huang, H., Chang, C., Liu, L., Shah, S. H., Torre, A. L., Welsbie, D. S., Sun, Y., Duan, X., Goldberg, J. L., Braun, M., Lansky, Z., Hu, Y. 2024

    Abstract

    Optineurin (OPTN) mutations are linked to amyotrophic lateral sclerosis (ALS) and normal tension glaucoma (NTG), but a relevant animal model is lacking, and the molecular mechanisms underlying neurodegeneration are unknown. We found that OPTN C-terminus truncation (OPTN∆C) causes late-onset neurodegeneration of retinal ganglion cells (RGCs), optic nerve (ON), and spinal cord motor neurons, preceded by a striking decrease of axonal mitochondria. Surprisingly, we discover that OPTN directly interacts with both microtubules and the mitochondrial transport complex TRAK1/KIF5B, stabilizing them for proper anterograde axonal mitochondrial transport, in a C-terminus dependent manner. Encouragingly, overexpressing OPTN/TRAK1/KIF5B reverses not only OPTN truncation-induced, but also ocular hypertension-induced neurodegeneration, and promotes striking ON regeneration. Therefore, in addition to generating new animal models for NTG and ALS, our results establish OPTN as a novel facilitator of the microtubule-dependent mitochondrial transport necessary for adequate axonal mitochondria delivery, and its loss as the likely molecular mechanism of neurodegeneration.

    View details for DOI 10.1101/2024.04.02.587832

    View details for PubMedID 38617277

  • RGC-specific ATF4 and/or CHOP deletion rescues glaucomatous neurodegeneration and visual function. Molecular therapy. Nucleic acids Fang, F., Liu, P., Huang, H., Feng, X., Li, L., Sun, Y., Kaufman, R. J., Hu, Y. 2023; 33: 286-295

    Abstract

    Endoplasmic reticulum (ER) stress has been linked with various acute and chronic neurodegenerative diseases. We previously found that optic nerve (ON) injury and diseases induce neuronal ER stress in retinal ganglion cells (RGCs). We further demonstrated that germline deletion of CHOP preserves the structure and function of both RGC somata and axons in mouse glaucoma models. Here we report that RGC-specific deletion of CHOP and/or its upstream regulator ATF4 synergistically promotes RGC and ON survival and preserves visual function in mouse ON crush and silicone oil-induced ocular hypertension (SOHU) glaucoma models. Consistently, topical application of the ATF4/CHOP chemical inhibitor ISRIB or RGC-specific CRISPR-mediated knockdown of the ATF4 downstream effector Gadd45a also delivers significant neuroprotection in the SOHU glaucoma model. These studies suggest that blocking the neuronal intrinsic ATF4/CHOP axis of ER stress is a promising neuroprotection strategy for neurodegeneration.

    View details for DOI 10.1016/j.omtn.2023.07.015

    View details for PubMedID 37547290

  • Differential effects of SARM1 inhibition in traumatic glaucoma and EAE optic neuropathies. Molecular therapy. Nucleic acids Liu, P., Chen, W., Jiang, H., Huang, H., Liu, L., Fang, F., Li, L., Feng, X., Liu, D., Dalal, R., Sun, Y., Jafar-Nejad, P., Ling, K., Rigo, F., Ye, J., Hu, Y. 2023; 32: 13-27

    Abstract

    Optic neuropathy is a group of optic nerve (ON) diseases withprogressive degeneration of ON and retinal ganglion cells(RGCs). The lack of neuroprotective treatments is a central challenge for this leading cause of irreversible blindness. SARM1 (sterile alpha and TIR motif-containing protein 1) has intrinsic nicotinamide adenine dinucleotide (NAD+) hydrolase activity that causes axon degeneration by degrading axonal NAD+ significantly after activation by axon injury. SARM1 deletion is neuroprotective in many, but not all, neurodegenerative disease models. Here, we compare two therapy strategies for SARM1 inhibition, antisense oligonucleotide (ASO) and CRISPR, with germline SARM1 deletion in the neuroprotection of three optic neuropathy mouse models. This study reveals that, similar to germline SARM1 knockout in every cell, local retinal SARM1 ASO delivery and adeno-associated virus (AAV)-mediated RGC-specific CRISPR knockdown of SARM1 provide comparable neuroprotection to both RGC somata and axons in the silicone oil-induced ocular hypertension (SOHU) glaucoma model but only protect RGC axons, not somata, after traumatic ON injury. Surprisingly, neither of these two therapy strategies of SARM1 inhibition nor SARM1 germline knockout (KO) benefits RGC or ON survival in the experimental autoimmune encephalomyelitis (EAE)/optic neuritis model. Our studies therefore suggest that SARM1 inhibition by local ASO delivery or AAV-mediated CRISPR is a promising neuroprotective gene therapy strategy for traumatic and glaucomatous optic neuropathies but not for demyelinating optic neuritis.

    View details for DOI 10.1016/j.omtn.2023.02.029

    View details for PubMedID 36950280

  • Neuroprotection of RGC-specific ATF4 Deletion in Mouse Glaucoma Model Li, L., Fang, F., Liu, P., Huang, H., Feng, X., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2023

    View details for Web of Science ID 001053758305168

  • Silicone Oil-Induced Glaucomatous Neurodegeneration in Rhesus Macaques. International journal of molecular sciences Moshiri, A., Fang, F., Zhuang, P., Huang, H., Feng, X., Li, L., Dalal, R., Hu, Y. 2022; 23 (24)

    Abstract

    Previously, we developed a simple procedure of intracameral injection of silicone oil (SO) into mouse eyes and established the mouse SOHU (SO-induced ocular hypertension under-detected) glaucoma model with reversible intraocular pressure (IOP) elevation and significant glaucomatous neurodegeneration. Because the anatomy of the non-human primate (NHP) visual system closely resembles that of humans, it is the most likely to predict human responses to diseases and therapies. Here we tried to replicate the mouse SOHU glaucoma model in rhesus macaque monkeys. All six animals that we tested showed significant retinal ganglion cell (RGC) death, optic nerve (ON) degeneration, and visual functional deficits at both 3 and 6 months. In contrast to the mouse SOHU model, however, IOP changed dynamically in these animals, probably due to individual differences in ciliary body tolerance capability. Further optimization of this model is needed to achieve consistent IOP elevation without permanent damage of the ciliary body. The current form of the NHP SOHU model recapitulates the severe degeneration of acute human glaucoma, and is therefore suitable for assessing experimental therapies for neuroprotection and regeneration, and therefore for translating relevant findings into novel and effective treatments for patients with glaucoma and other neurodegenerations.

    View details for DOI 10.3390/ijms232415896

    View details for PubMedID 36555536

  • Longitudinal in vivo Ca2+ imaging reveals dynamic activity changes of diseased retinal ganglion cells at the single-cell level. Proceedings of the National Academy of Sciences of the United States of America Li, L., Feng, X., Fang, F., Miller, D. A., Zhang, S., Zhuang, P., Huang, H., Liu, P., Liu, J., Sredar, N., Liu, L., Sun, Y., Duan, X., Goldberg, J. L., Zhang, H. F., Hu, Y. 2022; 119 (48): e2206829119

    Abstract

    Retinal ganglion cells (RGCs) are heterogeneous projection neurons that convey distinct visual features from the retina to brain. Here, we present a high-throughput in vivo RGC activity assay in response to light stimulation using noninvasive Ca2+ imaging of thousands of RGCs simultaneously in living mice. Population and single-cell analyses of longitudinal RGC Ca2+ imaging reveal distinct functional responses of RGCs and unprecedented individual RGC activity conversions during traumatic and glaucomatous degeneration. This study establishes a foundation for future in vivo RGC function classifications and longitudinal activity evaluations using more advanced imaging techniques and visual stimuli under normal, disease, and neural repair conditions. These analyses can be performed at both the population and single-cell levels using temporal and spatial information, which will be invaluable for understanding RGC pathophysiology and identifying functional biomarkers for diverse optic neuropathies.

    View details for DOI 10.1073/pnas.2206829119

    View details for PubMedID 36409915

  • Maprotiline restores ER homeostasis and rescues neurodegeneration via Histamine Receptor H1 inhibition in retinal ganglion cells. Nature communications Chen, W., Liu, P., Liu, D., Huang, H., Feng, X., Fang, F., Li, L., Wu, J., Liu, L., Solow-Cordero, D. E., Hu, Y. 2022; 13 (1): 6796

    Abstract

    When the protein or calcium homeostasis of the endoplasmic reticulum (ER) is adversely altered, cells experience ER stress that leads to various diseases including neurodegeneration. Genetic deletion of an ER stress downstream effector, CHOP, significantly protects neuron somata and axons. Here we report that three tricyclic compounds identified through a small-scale high throughput screening using a CHOP promoter-driven luciferase cell-based assay, effectively inhibit ER stress by antagonizing their common target, histamine receptor H1 (HRH1). We further demonstrated that systemic administration of one of these compounds, maprotiline, or CRISPR-mediated retinal ganglion cell (RGC)-specific HRH1 inhibition, delivers considerable neuroprotection of both RGC somata and axons and preservation of visual function in two mouse optic neuropathy models. Finally, we determine that maprotiline restores ER homeostasis by inhibiting HRH1-mediated Ca2+ release from ER. In this work we establish maprotiline as a candidate neuroprotectant and HRH1 as a potential therapeutic target for glaucoma.

    View details for DOI 10.1038/s41467-022-34682-y

    View details for PubMedID 36357388

  • Single-cell transcriptome analysis of regenerating RGCs reveals potent glaucoma neural repair genes. Neuron Li, L., Fang, F., Feng, X., Zhuang, P., Huang, H., Liu, P., Liu, L., Xu, A. Z., Qi, L. S., Cong, L., Hu, Y. 2022

    Abstract

    Axon regeneration holds great promise for neural repair of CNS axonopathies, including glaucoma. Pten deletion in retinal ganglion cells (RGCs) promotes potent optic nerve regeneration, but only a small population of Pten-null RGCs are actually regenerating RGCs (regRGCs); most surviving RGCs (surRGCs) remain non-regenerative. Here, we developed a strategy to specifically label and purify regRGCs and surRGCs, respectively, from the same Pten-deletion mice after optic nerve crush, in which they differ only in their regeneration capability. Smart-Seq2 single-cell transcriptome analysis revealed novel regeneration-associated genes that significantly promote axon regeneration. The most potent of these, Anxa2, acts synergistically with its ligand tPA in Pten-deletion-induced axon regeneration. Anxa2, its downstream effector ILK, and Mpp1 dramatically protect RGC somata and axons and preserve visual function in a clinically relevant model of glaucoma, demonstrating the exciting potential of this innovative strategy to identify novel effective neural repair candidates.

    View details for DOI 10.1016/j.neuron.2022.06.022

    View details for PubMedID 35952672

  • NMNAT2 and NAD(+) are Downregulated in Glaucomatous RGCs and Overexpression of NMNAT2 Rescues Glaucomatous Neurodegeneration Liu, D., Fang, F., Zhuang, P., Feng, X., Liu, P., Huang, H., Li, L., Chen, W., Liu, L., Sun, Y., Jiang, H., Ye, J., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022

    View details for Web of Science ID 000844401303120

  • Neuroprotection of SARM1 Inhibition in Traumatic and Glaucomatous but not in EAE Optic Neuropathies Liu, P., Huang, H., Chen, W., Fang, F., Li, L., Feng, X., Liu, L., Liu, D., Dalal, R., Sun, Y., Ling, K., Rigo, F., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022

    View details for Web of Science ID 000844401303121

  • In Vivo Evaluation of Naive and Diseased RGC Activities at Single-Cell Level Li, L., Fang, F., Feng, X., Zhang, S., Miller, D., Zhuang, P., Huang, H., Liu, P., Liu, J., Sredar, N., Liu, L., Sun, Y., Duan, X., Goldberg, J. L., Zhang, H., Hu, Y. ASSOC RESEARCH VISION OPHTHALMOLOGY INC. 2022

    View details for Web of Science ID 000844401305210

  • NMNAT2 Is Downregulated in Glaucomatous RGCs and RGC-Specific Gene Therapy Rescues Neurodegeneration and Visual Function. Molecular therapy : the journal of the American Society of Gene Therapy Fang, F., Zhuang, P., Feng, X., Liu, P., Liu, D., Huang, H., Li, L., Chen, W., Liu, L., Sun, Y., Jiang, H., Ye, J., Hu, Y. 1800

    Abstract

    The lack of neuroprotective treatments for retinal ganglion cells (RGCs) and optic nerve (ON) is a central challenge for glaucoma management. Emerging evidence suggests that redox factor NAD+ decline is a hallmark of aging and neurodegenerative diseases. Supplementation with NAD+ precursors and overexpression of NMNAT1, the key enzyme in the NAD+ biosynthetic process, have significant neuroprotective effects. We first profile the translatomes of RGCs in naive mice and mice with silicone oil-induced ocular hypertension (SOHU)/glaucoma by RiboTag mRNA sequencing. Intriguingly, only NMNAT2, but not NMNAT1 or NMNAT3, is significantly decreased in SOHU glaucomatous RGCs, which we confirm by in situ hybridization. We next demonstrate that AAV2 intravitreal injection-mediated overexpression of long half-life NMNAT2 mutant driven by RGC-specific mouse gamma-synuclein (mSncg) promoter restores decreased NAD+ levels in glaucomatous RGCs and ONs. Moreover, this RGC-specific gene therapy strategy delivers significant neuroprotection of both RGC soma and axon and preservation of visual function in the traumatic ON crush model and the SOHU glaucoma model. Collectively, our studies suggest that the weakening of NMNAT2 expression in glaucomatous RGCs contributes to a deleterious NAD+ decline and that modulating RGC intrinsic NMNAT2 levels by AAV2-mSncg vector is a promising gene therapy for glaucomatous neurodegeneration.

    View details for DOI 10.1016/j.ymthe.2022.01.035

    View details for PubMedID 35114390

  • Neuronal NMNAT2 Overexpression Does Not Achieve Significant Neuroprotection in Experimental Autoimmune Encephalomyelitis/Optic Neuritis. Frontiers in cellular neuroscience Liu, P., Huang, H., Fang, F., Liu, L., Li, L., Feng, X., Chen, W., Dalal, R., Sun, Y., Hu, Y. 2021; 15: 754651

    Abstract

    Optic neuritis, inflammation, and demyelination of the optic nerve (ON), is one of the most common clinical manifestations of multiple sclerosis; affected patients suffer persistent visual symptoms due to ON degeneration and secondary retinal ganglion cell (RGC) death. The mouse experimental autoimmune encephalomyelitis (EAE) model replicates optic neuritis and significant RGC soma and axon loss. Nicotinamide mononucleotide adenylyltransferases (NMNATs) are NAD+-synthetic enzymes that have been shown to be essential for axon integrity, activation of which significantly delays axonal Wallerian degeneration. NMNAT2, which is enriched in axons, has been proposed as a promising therapeutic target for axon injury-induced neurodegeneration. We therefore investigated whether activation of NMNAT2 can be used as a gene therapy strategy for neuroprotection in EAE/optic neuritis. To avoid the confounding effects in inflammatory cells, which play important roles in EAE initiation and progression, we used an RGC-specific promoter to drive the expression of the long half-life NMNAT2 mutant in mouse RGCs in vivo. However, optical coherence tomography in vivo retina imaging did not reveal significant protection of the ganglion cell complex, and visual function assays, pattern electroretinography, and optokinetic response also showed no improvement in mice with NMNAT2 overexpression. Postmortem histological analysis of retina wholemounts and semithin sections of ON confirmed the in vivo results: NMNAT2 activation in RGCs does not provide significant neuroprotection of RGCs in EAE/optic neuritis. Our studies suggest that a different degenerative mechanism than Wallerian degeneration is involved in autoimmune inflammatory axonopathy and that NMNAT2 may not be a major contributor to this mechanism.

    View details for DOI 10.3389/fncel.2021.754651

    View details for PubMedID 34707482