Project description:Leber’s hereditary optic neuropathy (LHON) is a maternally inherited mitochondrial disease caused by homoplasmic mutations in complex I subunit genes, and is characterized by incomplete penetrance. The mechanism of low penetrance of complex I mutation is still largely unclear today. In this study, we created the patient-specific induced pluripotent stem cells (iPSCs) from MT-ND4 mutated LHON affected patient, asymptomatic mutation carrier and control, and differentiated them into retinal ganglion cells (RGCs) for pathogenesis survey. We observed the following phenotypic features in the LHON-specific RGCs as compared to the control: 1) enhanced mitochondrial biogenesis in affected and carriers; 2) compensatory increased mitochondrial complex I activity in carrier, but not in affected patient; 3) reduced spare respiratory activity in affected and carrier. Microarray profiling of LHON-specific RGCs revealed abundant overexpression of genes encoding components of cell cycle regulation machinery as compared to the control.
Project description:LHON is a paraLeber hereditary optic neuropathy (LHON) is a paradigm for mitochondrial retinopathy due to mitochondrial DNA (mtDNA) mutations. However, the mechanism underlying retinal cell-specific effects of LHON-linked mtDNA mutations remains poorly understood and there has been no effective treatment or cure for this disorder. We use scRNA-seq to study the retinal cell-specific deficiencies caused by LHON-linked ND6P25L mutation.
Project description:Previous studies indicated that activation of glial cells and inflammatory responses are triggering factors of glaucomatous optic neuropathy. In particular, neurotoxic reactive astrocytes have been found to play a significant role in retinal ganglion cell damage. Furthermore, research showed that activation of glial cells is not dependent on retinal ganglion cell injury, but rather a direct response to pathological elevation of intraocular pressure. However, the molecular mechanism by which elevated intraocular pressure triggers glial activation through mechanical forces remains unknown. By spatial transcriptome sequencing, our study revealed that the neurotoxic astrocyte would rapidly be reactivated in the optic nerve head under elevated intraocular pressure in vivo.
Project description:Intercellular cytoplasmic material transfer (MT) occurs between transplanted and developing photoreceptors and ambiguates cell origin identification in developmental, transdifferentiation, and transplantation experiments. Whether MT is a photoreceptor-specific phenomenon is unclear. Retinal ganglion cell (RGC) replacement, through transdifferentiation or transplantation, holds potential for restoring vision in optic neuropathies. During careful assessment for MT following human stem cell-derived RGC transplantation into mice, we identified RGC xenografts occasionally giving rise to labeling of donor-derived cytoplasmic, nuclear, and mitochondrial proteins within recipient Müller glia. Critically, nuclear organization is distinct between human and murine retinal neurons, which enables unequivocal discrimination of donor from host cells. MT was dependent on internal limiting membrane disruption, which is also required for retinal engraftment following transplantation. Our findings demonstrate that retinal MT is not unique to photoreceptors and challenge the isolated use of species-specific immunofluorescent markers for xenotransplant identification. Assessment for MT is critical when analyzing neuronal replacement interventions.
Project description:Dnmt3a deficiency in retinal ganglion cells promotes axon regeneration in an optic nerve crush mouse model. To investigate the role of Dnmt3a in axon regeneration, retinal ganglion cell nuclei were sorted from control and retinal ganglion cell-specific Dnmt3a knockout mice at 2 days post optic nerve crush and applied for single nuclei RNA-seq analysis by 10X Genomics technology.
Project description:Glaucoma is an optic neuropathy characterized by progressive degeneration of retinal ganglion cells (RGCs) and visual loss. Previous studies have reported that the variation of the ATP-binding cassette transporter 1 (ABCA1) gene is linked to a higher risk of glaucoma in humans, but the pathological mechanisms remain unknown. Here we report that ABCA1 loss, especially in astrocytes, causes optic neuropathy. ABCA1 was mainly expressed in astrocytes rather than neurons, and that knockout of Abca1 gene under GFAP promoter (Glia-KO) caused age-associated RGC degeneration and ocular dysfunction without affecting intraocular pressure, a major risk factor for glaucoma. Glia-KO mice showed age-associated changes in astrocyte reactivity accompanied by the accumulation of cholesterol, a major substrate of ABCA1. Single-cell RNA sequencing revealed that Abca1 deficiency causes astrocyte-triggered inflammation and increased sensitivity of RGCs against excitotoxicity. Altogether, these findings suggest that astrocytic dysfunction caused by ABCA1 loss triggers age-associated optic neuropathy-like pathology.
Project description:Glaucoma is an optic neuropathy characterized by progressive degeneration of retinal ganglion cells (RGCs) and visual loss. Previous studies have reported that the variation of the ATP-binding cassette transporter 1 (ABCA1) gene is linked to a higher risk of glaucoma in humans, but the pathological mechanisms remain unknown. Here we report that ABCA1 loss, especially in astrocytes, causes optic neuropathy. ABCA1 was mainly expressed in astrocytes rather than neurons, and that knockout of Abca1 gene under GFAP promoter (Glia-KO) caused age-associated RGC degeneration and ocular dysfunction without affecting intraocular pressure, a major risk factor for glaucoma. Glia-KO mice showed age-associated changes in astrocyte reactivity accompanied by the accumulation of cholesterol, a major substrate of ABCA1. Single-cell RNA sequencing revealed that Abca1 deficiency causes astrocyte-triggered inflammation and increased sensitivity of RGCs against excitotoxicity. Altogether, these findings suggest that astrocytic dysfunction caused by ABCA1 loss triggers age-associated optic neuropathy-like pathology.
Project description:Autosomal optic atrophy (AOA) is a form of hereditary optic neuropathy characterized by the irreversible and progressive degermation of the retinal ganglion cells. Most cases of AOA are associated with a single dominant mutation in OPA1, which encodes a protein required for fusion of the inner mitochondrial membrane. It is unclear how loss of OPA1 leads to neuronal death, and despite ubiquitous expression appears to disproportionately affect the RGCs. This study introduces two novel in vivo models of OPA1-mediated AOA, including the first developmentally viable vertebrate Opa1 knockout (KO). These models allow for the study of Opa1 loss in neurons, specifically RGCs. Though survival is significantly reduced in Opa1 deficient zebrafish and Drosophila, both models permit the study of viable larvae. Moreover, zebrafish Opa1 KO larvae show impaired visual function but unchanged locomotor function, indicating that retinal neurons are particularly sensitive to Opa1 loss. Proteomic profiling of both models reveals marked disruption in protein expression associated with mitochondrial function, consistent with an observed decrease in mitochondrial respiratory function. Similarly, mitochondrial fragmentation and disordered cristae organization were observed in neuronal axons in both models highlighting Opa1’s highly conserved role in regulating mitochondrial morphology and function in neuronal axons. Importantly, in Opa1 deficient zebrafish, mitochondrial disruption and visual impairment precede degeneration of RGCs. These novel models mimic key features of AOA and provide valuable tools for therapeutic screening. Our findings suggest that therapies enhancing mitochondrial function may offer a potential treatment strategy for AOA.
Project description:Autosomal optic atrophy (AOA) is a form of hereditary optic neuropathy characterized by the irreversible and progressive degermation of the retinal ganglion cells. Most cases of AOA are associated with a single dominant mutation in OPA1, which encodes a protein required for fusion of the inner mitochondrial membrane. It is unclear how loss of OPA1 leads to neuronal death, and despite ubiquitous expression appears to disproportionately affect the RGCs. This study introduces two novel in vivo models of OPA1-mediated AOA, including the first developmentally viable vertebrate Opa1 knockout (KO). These models allow for the study of Opa1 loss in neurons, specifically RGCs. Though survival is significantly reduced in Opa1 deficient zebrafish and Drosophila, both models permit the study of viable larvae. Moreover, zebrafish Opa1 KO larvae show impaired visual function but unchanged locomotor function, indicating that retinal neurons are particularly sensitive to Opa1 loss. Proteomic profiling of both models reveals marked disruption in protein expression associated with mitochondrial function, consistent with an observed decrease in mitochondrial respiratory function. Similarly, mitochondrial fragmentation and disordered cristae organization were observed in neuronal axons in both models highlighting Opa1’s highly conserved role in regulating mitochondrial morphology and function in neuronal axons. Importantly, in Opa1 deficient zebrafish, mitochondrial disruption and visual impairment precede degeneration of RGCs. These novel models mimic key features of AOA and provide valuable tools for therapeutic screening. Our findings suggest that therapies enhancing mitochondrial function may offer a potential treatment strategy for AOA.