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mTORC1 Activation in Chx10-Specific Tsc1 Knockout Mice Accelerates Retina Aging and Degeneration. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:6715758. [PMID: 34777691 PMCID: PMC8589503 DOI: 10.1155/2021/6715758] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/14/2021] [Accepted: 10/25/2021] [Indexed: 11/23/2022]
Abstract
Age-associated decline in retina function is largely responsible for the irreversible vision deterioration in the elderly population. It is also an important risk factor for the development of degenerative and angiogenic diseases. However, the molecular mechanisms involved in the process of aging in the retina remain largely elusive. This study investigated the role of mTORC1 signaling in aging of the retina. We showed that mTORC1 was activated in old-aged retina, particularly in the ganglion cells. The role of mTORC1 activation was further investigated in Chx10-Cre;Tsc1fx/fx mouse (Tsc1-cKO). Activation of mTORC1 was found in bipolar and some of the ganglion and amacrine cells in the adult Tsc1-cKO retina. Bipolar cell hypertrophy and Müller gliosis were observed in Tsc1-cKO since 6 weeks of age. The abnormal endings of bipolar cell dendritic tips at the outer nuclear layer resembled that of the old-aged mice. Microglial cell activation became evident in 6-week-old Tsc1-cKO. At 5 months, the Tsc1-cKO mice exhibited advanced features of old-aged retina, including the expression of p16Ink4a and p21, expression of SA-β-gal in ganglion cells, decreased photoreceptor cell numbers, decreased electroretinogram responses, increased oxidative stress, microglial cell activation, and increased expression of immune and inflammatory genes. Inhibition of microglial cells by minocycline partially prevented photoreceptor cell loss and restored the electroretinogram responses. Collectively, our study showed that the activation of mTORC1 signaling accelerated aging of the retina by both cell autonomous and nonautonomous mechanisms. Our study also highlighted the role of microglia cells in driving the decline in retina function.
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Jones I, Hägglund AC, Carlsson L. Reduced mTORC1-signalling in retinal progenitor cells leads to visual pathway dysfunction. Biol Open 2019; 8:bio.044370. [PMID: 31285269 PMCID: PMC6737973 DOI: 10.1242/bio.044370] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Development of the vertebrate central nervous system involves the co-ordinated differentiation of progenitor cells and the establishment of functional neural networks. This neurogenic process is driven by both intracellular and extracellular cues that converge on the mammalian target of rapamycin complex 1 (mTORC1). Here we demonstrate that mTORC1-signalling mediates multi-faceted roles during central nervous system development using the mouse retina as a model system. Downregulation of mTORC1-signalling in retinal progenitor cells by conditional ablation of Rptor leads to proliferation deficits and an over-production of retinal ganglion cells during embryonic development. In contrast, reduced mTORC1-signalling in postnatal animals leads to temporal deviations in programmed cell death and the consequent production of asymmetric retinal ganglion cell mosaics and associated loss of axonal termination topographies in the dorsal lateral geniculate nucleus of adult mice. In combination these developmental defects induce visually mediated behavioural deficits. These collective observations demonstrate that mTORC1-signalling mediates critical roles during visual pathway development and function. Summary: Conditional deletion of Rptor in retinal progenitor cells demonstrates that mTORC1-signalling is critical for visual pathway development and function.
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Affiliation(s)
- Iwan Jones
- Umeå Center for Molecular Medicine (UCMM), Umeå University, 901 87 Umeå, Sweden
| | - Anna-Carin Hägglund
- Umeå Center for Molecular Medicine (UCMM), Umeå University, 901 87 Umeå, Sweden
| | - Leif Carlsson
- Umeå Center for Molecular Medicine (UCMM), Umeå University, 901 87 Umeå, Sweden
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Jones I, Novikova LN, Novikov LN, Renardy M, Ullrich A, Wiberg M, Carlsson L, Kingham PJ. Regenerative effects of human embryonic stem cell-derived neural crest cells for treatment of peripheral nerve injury. J Tissue Eng Regen Med 2018; 12:e2099-e2109. [PMID: 29327452 PMCID: PMC5947619 DOI: 10.1002/term.2642] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/02/2017] [Accepted: 01/02/2018] [Indexed: 12/12/2022]
Abstract
Surgical intervention is the current gold standard treatment following peripheral nerve injury. However, this approach has limitations, and full recovery of both motor and sensory modalities often remains incomplete. The development of artificial nerve grafts that either complement or replace current surgical procedures is therefore of paramount importance. An essential component of artificial grafts is biodegradable conduits and transplanted cells that provide trophic support during the regenerative process. Neural crest cells are promising support cell candidates because they are the parent population to many peripheral nervous system lineages. In this study, neural crest cells were differentiated from human embryonic stem cells. The differentiated cells exhibited typical stellate morphology and protein expression signatures that were comparable with native neural crest. Conditioned media harvested from the differentiated cells contained a range of biologically active trophic factors and was able to stimulate in vitro neurite outgrowth. Differentiated neural crest cells were seeded into a biodegradable nerve conduit, and their regeneration potential was assessed in a rat sciatic nerve injury model. A robust regeneration front was observed across the entire width of the conduit seeded with the differentiated neural crest cells. Moreover, the up-regulation of several regeneration-related genes was observed within the dorsal root ganglion and spinal cord segments harvested from transplanted animals. Our results demonstrate that the differentiated neural crest cells are biologically active and provide trophic support to stimulate peripheral nerve regeneration. Differentiated neural crest cells are therefore promising supporting cell candidates to aid in peripheral nerve repair.
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Affiliation(s)
- Iwan Jones
- Umeå Center for Molecular Medicine, Umeå University, Umeå, Sweden.,Laboratory of Neural Repair and Cellular Therapy, Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
| | - Liudmila N Novikova
- Laboratory of Neural Repair and Cellular Therapy, Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
| | - Lev N Novikov
- Laboratory of Neural Repair and Cellular Therapy, Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
| | - Monika Renardy
- ITV Denkendorf Product Service GmbH, Denkendorf, Germany
| | | | - Mikael Wiberg
- Laboratory of Neural Repair and Cellular Therapy, Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.,Hand and Plastic Surgery, Department of Surgical and Perioperative Sciences, Umeå University, Umeå, Sweden
| | - Leif Carlsson
- Umeå Center for Molecular Medicine, Umeå University, Umeå, Sweden
| | - Paul J Kingham
- Laboratory of Neural Repair and Cellular Therapy, Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
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Bykhovskaya Y, Fardaei M, Khaled ML, Nejabat M, Salouti R, Dastsooz H, Liu Y, Inaloo S, Rabinowitz YS. TSC1 Mutations in Keratoconus Patients With or Without Tuberous Sclerosis. Invest Ophthalmol Vis Sci 2017; 58:6462-6469. [PMID: 29261847 PMCID: PMC5760196 DOI: 10.1167/iovs.17-22819] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Purpose To test candidate genes TSC1 and TSC2 in a family affected by tuberous sclerosis complex (TSC) where proband was also diagnosed with bilateral keratoconus (KC) and to test the hypothesis that defects in the same gene may lead to a nonsyndromic KC. Methods Next-generation sequencing of TSC1 and TSC2 genes was performed in a proband affected by TSC and KC. Identified mutation was confirmed by Sanger DNA sequencing. Whole exome sequencing (WES) was performed in patients with nonsyndromic KC. Sanger DNA sequencing was used to confirm WES results and to screen additional patients. RT-PCR was used to investigate TSC1 expression in seven normal human corneas and eight corneas from patients with KC. Various in silico tools were employed to model functional consequences of identified mutations. Results A heterozygous nonsense TSC1 mutation g.132902703C>T (c.2293C>T, p.Gln765Ter) was identified in a patient with TSC and KC. Two heterozygous missense TSC1 variants g.132896322A>T (c.3408A>T, p.Asp1136Glu) and g.132896452G>A (c.3278G>A, p.Arg1093Gln) were identified in three patients with nonsyndromic KC. Two mutations were not present in The Genome Aggregation (GnomAD), The Exome Aggregation (ExAC), and 1000 Genomes (1000G) databases, while the third one was present in GnomAD and 1000G with minor allele frequencies (MAF) of 0.00001 and 0.0002, respectively. We found TSC1 expressed in normal corneas and KC corneas, albeit with various levels. Conclusions Here for the first time we found TSC1 gene to be involved in bilateral KC and TSC as well as with nonsyndromic KC, supporting the hypothesis that diverse germline mutations of the same gene can cause genetic disorders with overlapping clinical features.
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Affiliation(s)
- Yelena Bykhovskaya
- Department of Surgery and Board of the Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States.,Cornea Genetic Eye Institute, Beverly Hills, California, United States
| | - Majid Fardaei
- Department of Medical Genetics, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mariam Lotfy Khaled
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, Georgia, United States
| | - Mahmood Nejabat
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Ramin Salouti
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Hassan Dastsooz
- Comprehensive Medical Genetics Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Yutao Liu
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, Georgia, United States
| | - Soroor Inaloo
- Department of Pediatrics, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Yaron S Rabinowitz
- Department of Surgery and Board of the Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States.,Cornea Genetic Eye Institute, Beverly Hills, California, United States.,The Jules Stein Eye Institute, University of California-Los Angeles, Los Angeles, California, United States
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Hägglund AC, Jones I, Carlsson L. A novel mouse model of anterior segment dysgenesis (ASD): conditional deletion of Tsc1 disrupts ciliary body and iris development. Dis Model Mech 2017; 10:245-257. [PMID: 28250050 PMCID: PMC5374326 DOI: 10.1242/dmm.028605] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 01/05/2017] [Indexed: 12/22/2022] Open
Abstract
Development of the cornea, lens, ciliary body and iris within the anterior segment of the eye involves coordinated interaction between cells originating from the ciliary margin of the optic cup, the overlying periocular mesenchyme and the lens epithelium. Anterior segment dysgenesis (ASD) encompasses a spectrum of developmental syndromes that affect these anterior segment tissues. ASD conditions arise as a result of dominantly inherited genetic mutations and result in both ocular-specific and systemic forms of dysgenesis that are best exemplified by aniridia and Axenfeld-Rieger syndrome, respectively. Extensive clinical overlap in disease presentation amongst ASD syndromes creates challenges for correct diagnosis and classification. The use of animal models has therefore proved to be a robust approach for unravelling this complex genotypic and phenotypic heterogeneity. However, despite these successes, it is clear that additional genes that underlie several ASD syndromes remain unidentified. Here, we report the characterisation of a novel mouse model of ASD. Conditional deletion of Tsc1 during eye development leads to a premature upregulation of mTORC1 activity within the ciliary margin, periocular mesenchyme and lens epithelium. This aberrant mTORC1 signalling within the ciliary margin in particular leads to a reduction in the number of cells that express Pax6, Bmp4 and Msx1 Sustained mTORC1 signalling also induces a decrease in ciliary margin progenitor cell proliferation and a consequent failure of ciliary body and iris development in postnatal animals. Our study therefore identifies Tsc1 as a novel candidate ASD gene. Furthermore, the Tsc1-ablated mouse model also provides a valuable resource for future studies concerning the molecular mechanisms underlying ASD and acts as a platform for evaluating therapeutic approaches for the treatment of visual disorders.
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Affiliation(s)
- Anna-Carin Hägglund
- Umeå Center for Molecular Medicine (UCMM), Umeå University, Umeå 901 87, Sweden
| | - Iwan Jones
- Umeå Center for Molecular Medicine (UCMM), Umeå University, Umeå 901 87, Sweden
| | - Leif Carlsson
- Umeå Center for Molecular Medicine (UCMM), Umeå University, Umeå 901 87, Sweden
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Teotia P, Van Hook MJ, Wichman CS, Allingham RR, Hauser MA, Ahmad I. Modeling Glaucoma: Retinal Ganglion Cells Generated from Induced Pluripotent Stem Cells of Patients with SIX6 Risk Allele Show Developmental Abnormalities. Stem Cells 2017; 35:2239-2252. [PMID: 28792678 DOI: 10.1002/stem.2675] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/14/2017] [Accepted: 07/18/2017] [Indexed: 01/01/2023]
Abstract
Glaucoma represents a group of multifactorial diseases with a unifying pathology of progressive retinal ganglion cell (RGC) degeneration, causing irreversible vision loss. To test the hypothesis that RGCs are intrinsically vulnerable in glaucoma, we have developed an in vitro model using the SIX6 risk allele carrying glaucoma patient-specific induced pluripotent stem cells (iPSCs) for generating functional RGCs. Here, we demonstrate that the efficiency of RGC generation by SIX6 risk allele iPSCs is significantly lower than iPSCs-derived from healthy, age- and sex-matched controls. The decrease in the number of RGC generation is accompanied by repressed developmental expression of RGC regulatory genes. The SIX6 risk allele RGCs display short and simple neurites, reduced expression of guidance molecules, and immature electrophysiological signature. In addition, these cells have higher expression of glaucoma-associated genes, CDKN2A and CDKN2B, suggesting an early onset of the disease phenotype. Consistent with the developmental abnormalities, the SIX6 risk allele RGCs display global dysregulation of genes which map on developmentally relevant biological processes for RGC differentiation and signaling pathways such as mammalian target of rapamycin that integrate diverse functions for differentiation, metabolism, and survival. The results suggest that SIX6 influences different stages of RGC differentiation and their survival; therefore, alteration in SIX6 function due to the risk allele may lead to cellular and molecular abnormalities. These abnormalities, if carried into adulthood, may make RGCs vulnerable in glaucoma. Stem Cells 2017;35:2239-2252.
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Affiliation(s)
- Pooja Teotia
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Matthew J Van Hook
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Christopher S Wichman
- Department of Biostatistics, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - R Rand Allingham
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Michael A Hauser
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Iqbal Ahmad
- Department of Ophthalmology and Visual Sciences, College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska, USA
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Tee AR, Sampson JR, Pal DK, Bateman JM. The role of mTOR signalling in neurogenesis, insights from tuberous sclerosis complex. Semin Cell Dev Biol 2016; 52:12-20. [PMID: 26849906 DOI: 10.1016/j.semcdb.2016.01.040] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 01/05/2016] [Accepted: 01/25/2016] [Indexed: 11/30/2022]
Abstract
Understanding the development and function of the nervous system is one of the foremost aims of current biomedical research. The nervous system is generated during a relatively short period of intense neurogenesis that is orchestrated by a number of key molecular signalling pathways. Even subtle defects in the activity of these molecules can have serious repercussions resulting in neurological, neurodevelopmental and neurocognitive problems including epilepsy, intellectual disability and autism. Tuberous sclerosis complex (TSC) is a monogenic disease characterised by these problems and by the formation of benign tumours in multiple organs, including the brain. TSC is caused by mutations in the TSC1 or TSC2 gene leading to activation of the mechanistic target of rapamycin (mTOR) signalling pathway. A desire to understand the neurological manifestations of TSC has stimulated research into the role of the mTOR pathway in neurogenesis. In this review we describe TSC neurobiology and how the use of animal model systems has provided insights into the roles of mTOR signalling in neuronal differentiation and migration. Recent progress in this field has identified novel mTOR pathway components regulating neuronal differentiation. The roles of mTOR signalling and aberrant neurogenesis in epilepsy are also discussed. Continuing efforts to understand mTOR neurobiology will help to identify new therapeutic targets for TSC and other neurological diseases.
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Affiliation(s)
- Andrew R Tee
- Institute of Cancer & Genetics, Cardiff University School of Medicine, Institute of Medical Genetics Building, Heath Park, Cardiff CF14 4XN UK
| | - Julian R Sampson
- Institute of Cancer & Genetics, Cardiff University School of Medicine, Institute of Medical Genetics Building, Heath Park, Cardiff CF14 4XN UK
| | - Deb K Pal
- Department of Basic & Clinical Neurosciences, Institute of Psychiatry, Psychology & Neuroscience, King's College, London SE5 8RX UK
| | - Joseph M Bateman
- Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London SE1 1UL UK.
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