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Brown EE, Scandura MJ, Pierce EA. Expression of NMNAT1 in the photoreceptors is sufficient to prevent NMNAT1-associated retinal degeneration. Mol Ther Methods Clin Dev 2023; 29:319-328. [PMID: 37214313 PMCID: PMC10193288 DOI: 10.1016/j.omtm.2023.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 04/12/2023] [Indexed: 05/24/2023]
Abstract
Nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) is a ubiquitously expressed enzyme involved in nuclear NAD+ production throughout the body. However, mutations in the NMNAT1 gene lead to retina-specific disease with few reports of systemic effects. We have previously demonstrated that AAV-mediated gene therapy using self-complementary AAV (scAAV) to ubiquitously express NMNAT1 throughout the retina prevents retinal degeneration in a mouse model of NMNAT1-associated disease. We aimed to develop a better understanding of the cell types in the retina that contribute to disease pathogenesis in NMNAT1-associated disease, and to identify the cell types that require NMNAT1 expression for therapeutic benefit. To achieve this goal, we treated Nmnat1V9M/V9M mice with scAAV using cell type-specific promoters to restrict NMNAT1 expression to distinct retinal cell types. We hypothesized that photoreceptors are uniquely vulnerable to NAD+ depletion due to mutations in NMNAT1. Consistent with this hypothesis, we identified that treatments that drove NMNAT1 expression in the photoreceptors led to preservation of retinal morphology. These findings suggest that gene therapies for NMNAT1-associated disease should aim to express NMNAT1 in the photoreceptor cells.
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Affiliation(s)
- Emily E. Brown
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear Harvard Medical School, Boston, MA 02114, USA
| | - Michael J. Scandura
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear Harvard Medical School, Boston, MA 02114, USA
| | - Eric A. Pierce
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear Harvard Medical School, Boston, MA 02114, USA
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Sadr Z, Ghasemi A, Rohani M, Alavi A. NMNAT1 and hereditary spastic paraplegia (HSP): expanding the phenotypic spectrum of NMNAT1 variants. Neuromuscul Disord 2023; 33:295-301. [PMID: 36871412 DOI: 10.1016/j.nmd.2023.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 02/05/2023] [Accepted: 02/06/2023] [Indexed: 02/10/2023]
Abstract
In the NAD biosynthetic network, the nicotinamide mononucleotide adenylyltransferase (NMNAT) enzyme fuels NAD as a co-substrate for a group of enzymes. Mutations in the nuclear-specific isoform, NMNAT1, have been extensively reported as the cause of Leber congenital amaurosis-type 9 (LCA9). However, there are no reports of NMNAT1 mutations causing neurological disorders by disrupting the maintenance of physiological NAD homeostasis in other types of neurons. In this study, for the first time, the potential association between a NMNAT1 variant and hereditary spastic paraplegia (HSP) is described. Whole-exome sequencing was performed for two affected siblings diagnosed with HSP. Runs of homozygosity (ROH) were detected. The shared variants of the siblings located in the homozygosity blocks were selected. The candidate variant was amplified and Sanger sequenced in the proband and other family members. Homozygous variant c.769G>A:p.(Glu257Lys) in NMNAT1, the most common variant of NMNAT1 in LCA9 patients, located in the ROH of chromosome 1, was detected as a probable disease-causing variant. After detection of the variant in NMNAT1, as a LCA9-causative gene, ophthalmological and neurological re-evaluations were performed. No ophthalmological abnormality was detected and the clinical manifestations of these patients were completely consistent with pure HSP. No NMNAT1 variant had ever been previously reported in HSP patients. However, NMNAT1 variants have been reported in a syndromic form of LCA which is associated with ataxia. In conclusion, our patients expand the clinical spectrum of NMNAT1 variants and represent the first evidence of the probable correlation between NMNAT1 variants and HSP.
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Affiliation(s)
- Zahra Sadr
- Genetics research center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Aida Ghasemi
- Genetics research center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Mohammad Rohani
- Department of Neurology, Iran University of Medical Sciences, Hazrat Rasool Hospital, Tehran, Iran.
| | - Afagh Alavi
- Genetics research center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.
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Brown EE, Scandura MJ, Pierce E. Role of Nuclear NAD + in Retinal Homeostasis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:235-239. [PMID: 37440039 DOI: 10.1007/978-3-031-27681-1_34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
The retina is one of the most metabolically active tissues and maintenance of metabolic homeostasis is critical for retinal function. Nicotinamide adenine dinucleotide (NAD+) is a cofactor that is required for key processes, including the electron transport chain, glycolysis, fatty acid oxidation, and redox reactions. NAD+ also acts as a co-substrate for enzymes involved in maintaining genomic DNA integrity and cellular homeostasis, including poly-ADP ribose polymerases (PARPs) and Sirtuins. This review highlights the importance of NAD+ in the retina, including the role of enzymes involved in NAD+ production in the retina and how NAD+-consuming enzymes may play a role in disease pathology. We also suggest a cell death pathway that may be common in multiple models of photoreceptor degeneration and highlight the role that NAD+ likely plays in this process. Finally, we explore future experimental approaches to enhance our understanding of the role of NAD+ in the retina.
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Affiliation(s)
- Emily E Brown
- Ocular Genomics Institute, Massachusetts Eye and Ear, Boston, MA, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Michael J Scandura
- Ocular Genomics Institute, Massachusetts Eye and Ear, Boston, MA, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Eric Pierce
- Ocular Genomics Institute, Massachusetts Eye and Ear, Boston, MA, USA.
- Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
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Brown EE, Scandura MJ, Mehrotra S, Wang Y, Du J, Pierce EA. Reduced nuclear NAD+ drives DNA damage and subsequent immune activation in the retina. Hum Mol Genet 2021; 31:1370-1388. [PMID: 34750622 DOI: 10.1093/hmg/ddab324] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/14/2021] [Accepted: 11/04/2021] [Indexed: 11/13/2022] Open
Abstract
Mutations in NMNAT1, a key enzyme involved in the synthesis of NAD+ in the nucleus, lead to an early onset severe inherited retinal degeneration (IRD). We aimed to understand the role of nuclear NAD+ in the retina and to identify the molecular mechanisms underlying NMNAT1-associated disease, using a mouse model that harbors the p.V9M mutation in Nmnat1 (Nmnat1V9M/V9M). We identified temporal transcriptional reprogramming in the retinas of Nmnat1V9M/V9M mice prior to retinal degeneration, which begins at 4 weeks of age, with no significant alterations in gene expression at 2 weeks of age and over 2600 differentially expressed genes by 3 weeks of age. Expression of the primary consumer of NAD+ in the nucleus, PARP1, an enzyme involved in DNA damage repair and transcriptional regulation, as well as 7 other PARP family enzymes, was elevated in the retinas of Nmnat1V9M/V9M. This was associated with elevated levels of DNA damage, PARP-mediated NAD+ consumption, and migration of Iba1+/CD45+ microglia/macrophages to the subretinal space in the retinas of Nmnat1V9M/V9M mice. These findings suggest that photoreceptor cells are especially sensitive to perturbation of genome homeostasis, and that PARP-mediated cell death may play a role in other genetic forms of IRDs, and potentially other forms of neurodegeneration.
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Affiliation(s)
- Emily E Brown
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, 02114, USA
| | - Michael J Scandura
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, 02114, USA
| | - Sudeep Mehrotra
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, 02114, USA
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA.,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA.,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA
| | - Eric A Pierce
- Ocular Genomics Institute, Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, 02114, USA
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