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Williams LJ, Waller S, Qiu J, Innes E, Elserafy N, Procopis P, Sampaio H, Mahant N, Tchan MC, Mohammad SS, Morales‐Briceño H, Fung VS. DHDDS and NUS1: A Converging Pathway and Common Phenotype. Mov Disord Clin Pract 2024; 11:76-85. [PMID: 38291835 PMCID: PMC10828623 DOI: 10.1002/mdc3.13920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 08/11/2023] [Accepted: 10/23/2023] [Indexed: 02/01/2024] Open
Abstract
BACKGROUND Variants in dehydrodolichol diphosphate synthetase (DHDDS) and nuclear undecaprenyl pyrophosphate synthase 1 (NUS1) cause a neurodevelopmental disorder, classically with prominent epilepsy. Recent reports suggest a complex movement disorder and an overlapping phenotype has been postulated due to their combined role in dolichol synthesis. CASES We describe three patients with heterozygous variants in DHDDS and five with variants affecting NUS1. They bear a remarkably similar phenotype of a movement disorder dominated by multifocal myoclonus. Diagnostic clues include myoclonus exacerbated by action and facial involvement, and slowly progressive or stable, gait ataxia with disproportionately impaired tandem gait. Myoclonus is confirmed with neurophysiology, including EMG of facial muscles. LITERATURE REVIEW Ninety-eight reports of heterozygous variants in DHDDS, NUS1 and chromosome 6q22.1 structural alterations spanning NUS1, confirm the convergent phenotype of hypotonia at birth, developmental delay, multifocal myoclonus, ataxia, dystonia and later parkinsonism with or without generalized epilepsy. Other features include periodic exacerbations, stereotypies, anxiety, and dysmorphisms. Although their gene products contribute to dolichol biosynthesis, a key step in N-glycosylation, transferrin isoform profiles are typically normal. Imaging is normal or non-specific. CONCLUSIONS Recognition of their shared phenotype may expedite diagnosis through chromosomal microarray and by including DHDDS/NUS1 in movement disorder gene panels.
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Affiliation(s)
- Laura J. Williams
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
| | - Sophie Waller
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
| | - Jessica Qiu
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
| | - Emily Innes
- TY Nelson Department of Neurology and NeurosurgeryThe Children's Hospital at WestmeadWestmeadNew South WalesAustralia
- School of Medicine SydneyThe University of Notre DameSydneyNew South WalesAustralia
| | - Noha Elserafy
- Department of Genomic MedicineWestmead HospitalWestmeadNew South WalesAustralia
| | - Peter Procopis
- TY Nelson Department of Neurology and NeurosurgeryThe Children's Hospital at WestmeadWestmeadNew South WalesAustralia
- The Children's Hospital at Westmead Clinical School, Faculty of Medicine and HealthUniversity of SydneySydneyNew South WalesAustralia
| | - Hugo Sampaio
- Department of NeurologySydney Children's HospitalRandwickNew South WalesAustralia
- School of Women's and Children's HealthUniversity of New South WalesSydneyNew South WalesAustralia
| | - Neil Mahant
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
| | - Michel C. Tchan
- Department of Genomic MedicineWestmead HospitalWestmeadNew South WalesAustralia
- Specialty of Genomic Medicine, Faculty of Medicine and HealthThe University of SydneySydneyNew South WalesAustralia
| | - Shekeeb S. Mohammad
- TY Nelson Department of Neurology and NeurosurgeryThe Children's Hospital at WestmeadWestmeadNew South WalesAustralia
- Kids Neuroscience CentreThe Children's Hospital at WestmeadWestmeadNew South WalesAustralia
- Sydney Medical School, Faculty of Medicine and HealthUniversity of SydneySydneyNew South WalesAustralia
| | - Hugo Morales‐Briceño
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
| | - Victor S.C. Fung
- Movement Disorder Unit, Department of NeurologyWestmead HospitalWestmeadNew South WalesAustralia
- Sydney Medical School, Faculty of Medicine and HealthUniversity of SydneySydneyNew South WalesAustralia
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2
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Singh AK, Chaube B, Citrin KM, Fowler JW, Lee S, Catarino J, Knight J, Lowery S, Shree S, Boutagy N, Ruz-Maldonado I, Harry K, Shanabrough M, Ross TT, Malaker S, Suárez Y, Fernández-Hernando C, Grabinska K, Sessa WC. Loss of cis-PTase function in the liver promotes a highly penetrant form of fatty liver disease that rapidly transitions to hepatocellular carcinoma. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.13.566870. [PMID: 38014178 PMCID: PMC10680637 DOI: 10.1101/2023.11.13.566870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Obesity-linked fatty liver is a significant risk factor for hepatocellular carcinoma (HCC) 1,2 ; however, the molecular mechanisms underlying the transition from non-alcoholic fatty liver disease (NAFLD) to HCC remains unclear. The present study explores the role of the endoplasmic reticulum (ER)-associated protein NgBR, an essential component of the cis-prenyltransferases (cis-PTase) enzyme 3 , in chronic liver disease. Here we show that genetic depletion of NgBR in hepatocytes of mice (N-LKO) intensifies triacylglycerol (TAG) accumulation, inflammatory responses, ER/oxidative stress, and liver fibrosis, ultimately resulting in HCC development with 100% penetrance after four months on a high-fat diet. Comprehensive genomic and single cell transcriptomic atlas from affected livers provides a detailed molecular analysis of the transition from liver pathophysiology to HCC development. Importantly, pharmacological inhibition of diacylglycerol acyltransferase-2 (DGAT2), a key enzyme in hepatic TAG synthesis, abrogates diet-induced liver damage and HCC burden in N-LKO mice. Overall, our findings establish NgBR/cis-PTase as a critical suppressor of NAFLD-HCC conversion and suggests that DGAT2 inhibition may serve as a promising therapeutic approach to delay HCC formation in patients with advanced non-alcoholic steatohepatitis (NASH).
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3
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Ramachandra Rao S, Fliesler SJ. A simple, rapid fluorescent reporter-based method for detection of ectopic cre recombinase expression in presumed retinal cell type-targeted mouse lines. Exp Eye Res 2023; 235:109637. [PMID: 37659708 PMCID: PMC10756212 DOI: 10.1016/j.exer.2023.109637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/18/2023] [Accepted: 08/25/2023] [Indexed: 09/04/2023]
Abstract
Although cell type-specific Cre recombinase-expressing mouse lines are commonly used to generate conditional knockout of genes of interest, germline recombination and ectopic "leakiness" in Cre recombinase expression in non-specific cell types has been observed in several neuronal and glial-specific Cre lines. This often leads to inadvertent loss of conditional mouse lines, requiring rederivation. It is therefore imperative to be able to monitor and validate cell type-specific Cre recombinase-mediated gene editing. Herein, we describe a simple, inexpensive, rapid ZsGreen fluor-reporter-based strategy for genotype-free identification of ectopic leakiness using a custom-designed, 3-D blue LED light box. We assessed cell type-specific expression in several allegedly specific Cre recombinase mouse lines commonly used in vision research: retinal pigment epithelium (RPE)-specific (VMD2 (Best1) Cre, RPE65 Cre); astrocyte-specific (GFAP Cre); as well as photoreceptor-bipolar progenitor cell-specific (CRX Cre). Our standardized workflow allows facile, rapid identification of ectopic and non-specific Cre recombinase expression in any presume specific Cre mouse line, without the need for genotyping and without causing animal distress.
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Affiliation(s)
- Sriganesh Ramachandra Rao
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Research Service, VA Western New York Healthcare System, Buffalo, NY, USA
| | - Steven J Fliesler
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York - University at Buffalo, Buffalo, NY, USA; Research Service, VA Western New York Healthcare System, Buffalo, NY, USA.
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4
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Nguyen MN, Chakraborty D, Rao SR, Onysk A, Radkiewicz M, Surmacz L, Swiezewska E, Soubeyrand E, Akhtar TA, Kraft TW, Sherry DM, Fliesler SJ, Pittler SJ. A Dhdds K42E knock-in RP59 mouse model shows inner retina pathology and defective synaptic transmission. Cell Death Dis 2023; 14:420. [PMID: 37443173 PMCID: PMC10345138 DOI: 10.1038/s41419-023-05936-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 06/07/2023] [Accepted: 06/29/2023] [Indexed: 07/15/2023]
Abstract
Retinitis pigmentosa (RP) defines a group of hereditary progressive rod-cone degenerations that exhibit a common phenotype caused by variants in over 70 genes. While most variants in the dehydrodolichyl diphosphate synthase (DHDDS) gene result in syndromic abnormalities, some variants cause non-syndromic RP (RP59). DHDDS encodes one subunit of the enzyme cis-prenyltransferase (CPT), which is required for the synthesis of dolichol (Dol), that is a necessary protein glycosylation cofactor. We previously reported the creation and initial characterization of a knock-in (KI) mouse model harboring the most prevalent RP59-associated DHDDS variant (K42E) to understand how defects in DHDDS lead to retina-specific pathology. This model exhibited no profound retinal degeneration, nor protein N-glycosylation defects. Here, we report that the Dol isoprenylogue species in retina, liver, and brain of the K42E mouse model are statistically shorter than in the corresponding tissues of age-matched controls, as reported in blood and urine of RP59 patients. Retinal transcriptome analysis demonstrated elevation of many genes encoding proteins involved in synaptogenesis and synaptic function. Quantitative retinal cell layer thickness measurements demonstrated a significant reduction in the inner nuclear layer (INL) and total retinal thickness (TRT) beginning at postnatal (PN) ∼2 months, progressively increasing to PN 18-mo. Histological analysis revealed cell loss in the INL, outer plexiform layer (OPL) disruption, and ectopic localization of outer nuclear layer (ONL) nuclei into the OPL of K42E mutant retinas, relative to controls. Electroretinograms (ERGs) of mutant mice exhibited reduced b-wave amplitudes beginning at PN 1-mo, progressively declining through PN 18-mo, without appreciable a-wave attenuation, relative to controls. Our results suggest that the underlying cause of DHDDS K42E variant driven RP59 retinal pathology is defective synaptic transmission from outer to inner retina.
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Affiliation(s)
- Mai N Nguyen
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Dibyendu Chakraborty
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sriganesh Ramachandra Rao
- Research Service, VA Western New York Healthcare System, Buffalo, NY, 14215, USA
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, Buffalo, NY, 14203, USA
| | - Agnieszka Onysk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Mariusz Radkiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Liliana Surmacz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Ewa Swiezewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Eric Soubeyrand
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada
| | - Tariq A Akhtar
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada
| | - Timothy W Kraft
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - David M Sherry
- Departments of Cell Biology, Neurosurgery, and Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Steven J Fliesler
- Research Service, VA Western New York Healthcare System, Buffalo, NY, 14215, USA
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, Buffalo, NY, 14203, USA
| | - Steven J Pittler
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
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5
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Rao SR, Pittler SJ, Fliesler SJ. Perspectives on Retinal Dolichol Metabolism, and Visual Deficits in Dolichol Metabolism-Associated Inherited Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:449-456. [PMID: 37440071 DOI: 10.1007/978-3-031-27681-1_66] [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
De novo synthesis of dolichol (Dol) and dolichyl phosphate (Dol-P) is essential for protein glycosylation. Herein, we provide a brief overview of Dol and Dol-P synthesis and the maintenance of their cellular content. Retinal Dol metabolism and the requirement of Dol-linked oligosaccharide synthesis in the neural retina also are discussed. There are recently discovered and an emerging class of rare congenital disorders that affect Dol metabolism, involving the genes DHDDS, NUS1, SRD5A3, and DOLK. Further understanding of these congenital disorders is evolving, based upon studies utilizing yeast and murine models, as well as clinical reports of these rare disorders. We summarize the known visual deficits associated with Dol metabolism disorders, and identify the need for generation and characterization of suitable animal models of these disorders to elucidate the underlying molecular and cellular mechanisms of the associated retinopathies.
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Affiliation(s)
- Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry, and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York, Buffalo, NY, USA
- Research Service, VA Western NY Healthcare System, Buffalo, NY, USA
| | - Steven J Pittler
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry, and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York, Buffalo, NY, USA.
- Research Service, VA Western NY Healthcare System, Buffalo, NY, USA.
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6
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Farkas MH, Skelton LA, Ramachandra-Rao S, Au E, Fliesler SJ. Morphological, biochemical, and transcriptomic characterization of iPSC-derived human RPE cells from normal and Smith-Lemli-Opitz syndrome patients. Mol Vis 2022; 28:394-411. [PMID: 36540063 PMCID: PMC9744241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 11/11/2022] [Indexed: 12/30/2022] Open
Affiliation(s)
- Michael H. Farkas
- Department of Ophthalmology (Ross Eye Institute), The State University of New York- University at Buffalo, Buffalo, NY
- Department of Biochemistry and the Neuroscience Graduate Program, The State University of New York- University at Buffalo, Buffalo, NY
- Research Service, VA Western New York Healthcare System, Buffalo, NY
| | - Lara A. Skelton
- Department of Ophthalmology (Ross Eye Institute), The State University of New York- University at Buffalo, Buffalo, NY
- Department of Biochemistry and the Neuroscience Graduate Program, The State University of New York- University at Buffalo, Buffalo, NY
- Research Service, VA Western New York Healthcare System, Buffalo, NY
| | - Sriganesh Ramachandra-Rao
- Department of Ophthalmology (Ross Eye Institute), The State University of New York- University at Buffalo, Buffalo, NY
- Department of Biochemistry and the Neuroscience Graduate Program, The State University of New York- University at Buffalo, Buffalo, NY
- Research Service, VA Western New York Healthcare System, Buffalo, NY
| | - Elizabeth Au
- Department of Ophthalmology (Ross Eye Institute), The State University of New York- University at Buffalo, Buffalo, NY
| | - Steven J. Fliesler
- Department of Ophthalmology (Ross Eye Institute), The State University of New York- University at Buffalo, Buffalo, NY
- Department of Biochemistry and the Neuroscience Graduate Program, The State University of New York- University at Buffalo, Buffalo, NY
- Research Service, VA Western New York Healthcare System, Buffalo, NY
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7
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Fliesler SJ, Ramachandra Rao S, Nguyen MN, KhalafAllah MT, Pittler SJ. Vertebrate Animal Models of RP59: Current Status and Future Prospects. Int J Mol Sci 2022; 23:13324. [PMID: 36362109 PMCID: PMC9657489 DOI: 10.3390/ijms232113324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 10/27/2022] [Accepted: 10/28/2022] [Indexed: 09/20/2023] Open
Abstract
Retinitis pigmentosa-59 (RP59) is a rare, recessive form of RP, caused by mutations in the gene encoding DHDDS (dehydrodolichyl diphosphate synthase). DHDDS forms a heterotetrameric complex with Nogo-B receptor (NgBR; gene NUS1) to form a cis-prenyltransferase (CPT) enzyme complex, which is required for the synthesis of dolichol, which in turn is required for protein N-glycosylation as well as other glycosylation reactions in eukaryotic cells. Herein, we review the published phenotypic characteristics of RP59 models extant, with an emphasis on their ocular phenotypes, based primarily upon knock-in of known RP59-associated DHDDS mutations as well as cell type- and tissue-specific knockout of DHDDS alleles in mice. We also briefly review findings in RP59 patients with retinal disease and other patients with DHDDS mutations causing epilepsy and other neurologic disease. We discuss these findings in the context of addressing "knowledge gaps" in our current understanding of the underlying pathobiology mechanism of RP59, as well as their potential utility for developing therapeutic interventions to block the onset or to dampen the severity or progression of RP59.
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Affiliation(s)
- Steven J. Fliesler
- Departments of Ophthalmology and Biochemistry, Neuroscience Graduate Program, Jacobs School of Medicine, State University of New York—University at Buffalo, Buffalo, NY 14203, USA
- Research Service, VA Western NY Healthcare System, Buffalo, NY 14215, USA
| | - Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry, Neuroscience Graduate Program, Jacobs School of Medicine, State University of New York—University at Buffalo, Buffalo, NY 14203, USA
- Research Service, VA Western NY Healthcare System, Buffalo, NY 14215, USA
| | - Mai N. Nguyen
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Mahmoud Tawfik KhalafAllah
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Steven J. Pittler
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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8
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Hyde LF, Kong Y, Zhao L, Rao SR, Wang J, Stone L, Njaa A, Collin GB, Krebs MP, Chang B, Fliesler SJ, Nishina PM, Naggert JK. A Dpagt1 Missense Variant Causes Degenerative Retinopathy without Myasthenic Syndrome in Mice. Int J Mol Sci 2022; 23:12005. [PMID: 36233305 PMCID: PMC9570038 DOI: 10.3390/ijms231912005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/29/2022] [Accepted: 10/04/2022] [Indexed: 01/12/2023] Open
Abstract
Congenital disorders of glycosylation (CDG) are a heterogenous group of primarily autosomal recessive mendelian diseases caused by disruptions in the synthesis of lipid-linked oligosaccharides and their transfer to proteins. CDGs usually affect multiple organ systems and vary in presentation, even within families. There is currently no cure, and treatment is aimed at ameliorating symptoms and improving quality of life. Here, we describe a chemically induced mouse mutant, tvrm76, with early-onset photoreceptor degeneration. The recessive mutation was mapped to Chromosome 9 and associated with a missense mutation in the Dpagt1 gene encoding UDP-N-acetyl-D-glucosamine:dolichyl-phosphate N-acetyl-D-glucosaminephosphotransferase (EC 2.7.8.15). The mutation is predicted to cause a substitution of aspartic acid with glycine at residue 166 of DPAGT1. This represents the first viable animal model of a Dpagt1 mutation and a novel phenotype for a CDG. The increased expression of Ddit3, and elevated levels of HSPA5 (BiP) suggest the presence of early-onset endoplasmic reticulum (ER) stress. These changes were associated with the induction of photoreceptor apoptosis in tvrm76 retinas. Mutations in human DPAGT1 cause myasthenic syndrome-13 and severe forms of a congenital disorder of glycosylation Type Ij. In contrast, Dpagt1tvrm76 homozygous mice present with congenital photoreceptor degeneration without overt muscle or muscular junction involvement. Our results suggest the possibility of DPAGT1 mutations in human patients that present primarily with retinitis pigmentosa, with little or no muscle disease. Variants in DPAGT1 should be considered when evaluating cases of non-syndromic retinal degeneration.
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Affiliation(s)
| | - Yang Kong
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, ME 04469, USA
| | - Lihong Zhao
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
- Research Service, VA Western New York Healthcare System, Buffalo, NY 14215, USA
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Lisa Stone
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Andrew Njaa
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | | | - Mark P Krebs
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME 04609, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
- Research Service, VA Western New York Healthcare System, Buffalo, NY 14215, USA
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9
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Mousa J, Veres L, Mohamed A, De Graef D, Morava E. Acetazolamide treatment in late onset CDG type 1 due to biallelic pathogenic DHDDS variants. Mol Genet Metab Rep 2022; 32:100901. [PMID: 36046393 PMCID: PMC9421445 DOI: 10.1016/j.ymgmr.2022.100901] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 11/29/2022] Open
Abstract
Pathogenic variants in DHDDS have been associated with either autosomal recessive retinitis pigmentosa or DHDDS-CDG. Heterozygous variants in DHDDS have been described in patients with a progressive neurodegenerative disease. Here we report on an individual presenting with a multisystem CDG phenotype who was diagnosed with known homozygous pathogenic DHDDS variants, previously associated with isolated retinitis pigmentosa. An adult Ashkenazi Jewish female developed multiple symptoms of late onset type 1 CDG including seizures, ataxia, protein losing enteropathy, tremor, and titubation in association with elevated mono-oligo/di-oligo transferrin ratio in blood, and classic retinitis pigmentosa. She was diagnosed by whole exome sequencing with the common Ashkenazi Jewish, homozygous p.K42E variants in DHDDS. She was started on Acetazolamide and responded well to the treatment which improved her titubation, tremor, and generalized edema. Reviewing the literature, families with DHDDS variants and multisystem presentation were different from our patient's presentation in terms of clinical manifestations, severity, genetic defect, and mode of inheritance. In previously reported patients with neurologic symptoms including seizures, movement abnormalities, and global development delay, the phenotype was caused by heterozygous pathogenic variants in DHDDS. The infant who was reported with a multisystem phenotype and fatal type 1 CDG had compound heterozygosity for a nonsense and a splice site variant in DHDDS, resulting in DHDDS-CDG. The discovery of the novel phenotype associated with the common p.K42E pathogenic variant in DHDDS expands the spectrum of CDG and further enhances our understanding on the role of DHDDS in glycosylation beyond the retina. We report on the first individual carrying homozygous p.K42E variants in DHDDS associated with protein losing enteropathy, seizures, and ataxia. We observed familial variability in association with p.K42E and progressive ataxia in siblings with in DHDDS-CDG. The novel DHDDS-CDG patient phenotype broadens the current spectrum of CDG. Acetazolamide was successful in treating titubation and recurrent edema in our DHDDS-CDG patient of Ashkenazi Jewish descent.
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Affiliation(s)
- Jehan Mousa
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | - Larissa Veres
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | - Anab Mohamed
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
| | | | - Eva Morava
- Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
- Corresponding author at: Department of Clinical Genomics, Mayo Clinic, Rochester, MN, USA.
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10
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Lewandowski D, Sander CL, Tworak A, Gao F, Xu Q, Skowronska-Krawczyk D. Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life. Prog Retin Eye Res 2021; 89:101037. [PMID: 34971765 PMCID: PMC10361839 DOI: 10.1016/j.preteyeres.2021.101037] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 12/13/2022]
Abstract
The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.
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Affiliation(s)
- Dominik Lewandowski
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Christopher L Sander
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Aleksander Tworak
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Fangyuan Gao
- Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Qianlan Xu
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA
| | - Dorota Skowronska-Krawczyk
- Department of Physiology and Biophysics, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA; Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, UC Irvine, Irvine, CA, USA.
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Ramachandra Rao S, Fliesler SJ. Monitoring basal autophagy in the retina utilizing CAG-mRFP-EGFP-MAP1LC3B reporter mouse: technical and biological considerations. Autophagy 2021; 18:1187-1201. [PMID: 34674604 PMCID: PMC9196719 DOI: 10.1080/15548627.2021.1969634] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We describe the utility of a tandem-tagged autophagy reporter mouse model (CAG-RFP-EGFP-MAP1LC3B) in investigating basal macroautophagic/autophagic flux in the neural retina. Western blot, in situ hybridization, immunohistochemistry, and confocal microscopy showed that CAG promoter-driven expression of RFP-EGFP-MAP1LC3B increased “cytosolic” RFP-EGFP-LC3B-I levels, whereas RFP-EGFP-LC3B-II decorates true phagosomes. We verified that the electroretinographic (ERG) responses of tandem-tagged LC3B mice were comparable to those of age-matched controls. Optimized microscope settings detected lipofuscin autofluorescence in retinas of abca4−/- mice. The majority of retinal phagosomes in the reporter mice exhibited only RFP (not EGFP) fluorescence, suggesting rapid maturation of phagosomes. Only ~1.5% of the total phagosome population was EGFP-labeled; RFP-labeled (mature) phagosomes colocalized with lysosomal markers LAMP2 and CTSD. In the outer retina, phagosome sizes were as follows (in µm2, ave ± SEM): RPE, 0.309 ± 0.015; photoreceptor inner segment-myoid, 0.544 ± 0.031; and outer nuclear layer, 0.429 ± 0.011. Detection of RPE phagosomes by fluorescence microscopy is challenging, due to the presence of melanin. Increased lipofuscin autofluorescence, such as observed in the abca4−/- mouse model of Stargardt disease, is a strong confounding factor when attempting to study autophagy in the RPE. In addition to RPE and photoreceptor cells, phagosomes were detected in inner retinal cell types, microglia, astrocytes, and endothelial cells. We conclude that the tandem-tagged LC3B mouse model serves as a useful system for studying autophagy in the retina. This utility, however, is dependent upon several technical and biological factors, including microscope settings, transgene expression, choice of fluorophores, and lipofuscin autofluorescence. Abbreviations: ACTB: actin, beta; AIF1: allograft inflammatory factor 1; ATG: autophagy related; CTSD: cathepsin D; DAPI: (4’,6-diamido-2-phenylindole); DIC: differential interference contrast; EGFP: enhanced green fluorescent protein; ELM: external limiting membrane; ERG: electroretinography; GCL: ganglion cell layer; GLUL: glutamine-ammonia ligase (glutamine synthetase); INL: inner nuclear layer; IS-E/M: inner segment – ellipsoid/myoid; ISH: in situ hybridization; LAMP2: lysosomal-associated membrane protein 2; L.I.: laser Intensity; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; O.C.T.: optimal cutting temperature; OS: outer segment; ONL: outer nuclear layer; PE: phosphatidylethanolamine; RFP: red fluorescent protein; R.O.I.: region of interest; RPE: retinal pigment epithelium
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Affiliation(s)
- Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA.,Research Service, VA Western Ny Healthcare System, Buffalo, NY, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA.,Research Service, VA Western Ny Healthcare System, Buffalo, NY, USA
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12
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Brandwine T, Ifrah R, Bialistoky T, Zaguri R, Rhodes-Mordov E, Mizrahi-Meissonnier L, Sharon D, Katanaev VL, Gerlitz O, Minke B. Knockdown of Dehydrodolichyl Diphosphate Synthase in the Drosophila Retina Leads to a Unique Pattern of Retinal Degeneration. Front Mol Neurosci 2021; 14:693967. [PMID: 34290587 PMCID: PMC8287061 DOI: 10.3389/fnmol.2021.693967] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 06/14/2021] [Indexed: 01/30/2023] Open
Abstract
Dehydrodolichyl diphosphate synthase (DHDDS) is a ubiquitously expressed enzyme that catalyzes cis-prenyl chain elongation to produce the poly-prenyl backbone of dolichol. It appears in all tissues including the nervous system and it is a highly conserved enzyme that can be found in all animal species. Individuals who have biallelic missense mutations in the DHDDS gene are presented with non-syndromic retinitis pigmentosa with unknown underlying mechanism. We have used the Drosophila model to compromise DHDDS ortholog gene (CG10778) in order to look for cellular and molecular mechanisms that, when defective, might be responsible for this retinal disease. The Gal4/UAS system was used to suppress the expression of CG10778 via RNAi-mediated-knockdown in various tissues. The resulting phenotypes were assessed using q-RT-PCR, transmission-electron-microscopy (TEM), electroretinogram, antibody staining and Western blot analysis. Targeted knockdown of CG10778-mRNA in the early embryo using the actin promoter or in the developing wings using the nub promoter resulted in lethality, or wings loss, respectively. Targeted expression of CG10778-RNAi using the glass multiple reporter (GMR)-Gal4 driver (GMR-DHDDS-RNAi) in the larva eye disc and pupal retina resulted in a complex phenotype: (a) TEM retinal sections revealed a unique pattern of retinal-degeneration, where photoreceptors R2 and R5 exhibited a nearly normal structure of their signaling-compartment (rhabdomere), but only at the region of the nucleus, while all other photoreceptors showed retinal degeneration at all regions. (b) Western blot analysis revealed a drastic reduction in rhodopsin levels in GMR-DHDDS-RNAi-flies and TEM sections showed an abnormal accumulation of endoplasmic reticulum (ER). To conclude, compromising DHDDS in the developing retina, while allowing formation of the retina, resulted in a unique pattern of retinal degeneration, characterized by a dramatic reduction in rhodopsin protein level and an abnormal accumulation of ER membranes in the photoreceptors cells, thus indicating that DHDDS is essential for normal retinal formation.
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Affiliation(s)
- Tal Brandwine
- Department of Medical Neurobiology, Faculty of Medicine and The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Reut Ifrah
- Department of Medical Neurobiology, Faculty of Medicine and The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tzofia Bialistoky
- Department of Developmental Biology and Cancer Research, Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rachel Zaguri
- Department of Medical Neurobiology, Faculty of Medicine and The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Elisheva Rhodes-Mordov
- Department of Medical Neurobiology, Faculty of Medicine and The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Liliana Mizrahi-Meissonnier
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Vladimir L Katanaev
- Department of Cell Physiology and Metabolism, Translational Research Centre in Oncohaematology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
| | - Offer Gerlitz
- Department of Developmental Biology and Cancer Research, Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Baruch Minke
- Department of Medical Neurobiology, Faculty of Medicine and The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem, Jerusalem, Israel
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13
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Abstract
Cholesterol is a quantitatively and biologically significant constituent of all mammalian cell membrane, including those that comprise the retina. Retinal cholesterol homeostasis entails the interplay between de novo synthesis, uptake, intraretinal sterol transport, metabolism, and efflux. Defects in these complex processes are associated with several congenital and age-related disorders of the visual system. Herein, we provide an overview of the following topics: (a) cholesterol synthesis in the neural retina; (b) lipoprotein uptake and intraretinal sterol transport in the neural retina and the retinal pigment epithelium (RPE); (c) cholesterol efflux from the neural retina and the RPE; and (d) biology and pathobiology of defects in sterol synthesis and sterol oxidation in the neural retina and the RPE. We focus, in particular, on studies involving animal models of monogenic disorders pertinent to the above topics, as well as in vitro models using biochemical, metabolic, and omic approaches. We also identify current knowledge gaps and opportunities in the field that beg further research in this topic area.
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Affiliation(s)
- Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA.
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Structural basis of heterotetrameric assembly and disease mutations in the human cis-prenyltransferase complex. Nat Commun 2020; 11:5273. [PMID: 33077723 PMCID: PMC7573591 DOI: 10.1038/s41467-020-18970-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/23/2020] [Indexed: 11/17/2022] Open
Abstract
The human cis-prenyltransferase (hcis-PT) is an enzymatic complex essential for protein N-glycosylation. Synthesizing the precursor of the glycosyl carrier dolichol-phosphate, mutations in hcis-PT cause severe human diseases. Here, we reveal that hcis-PT exhibits a heterotetrameric assembly in solution, consisting of two catalytic dehydrodolichyl diphosphate synthase (DHDDS) and inactive Nogo-B receptor (NgBR) heterodimers. Importantly, the 2.3 Å crystal structure reveals that the tetramer assembles via the DHDDS C-termini as a dimer-of-heterodimers. Moreover, the distal C-terminus of NgBR transverses across the interface with DHDDS, directly participating in active-site formation and the functional coupling between the subunits. Finally, we explored the functional consequences of disease mutations clustered around the active-site, and in combination with molecular dynamics simulations, we propose a mechanism for hcis-PT dysfunction in retinitis pigmentosa. Together, our structure of the hcis-PT complex unveils the dolichol synthesis mechanism and its perturbation in disease. The human cis-prenyltransferase (hcis-PT) complex synthesizes the precursor of the glycosyl carrier dolichol-phosphate and as such it is essential for protein N-glycosylation. The crystal structure of the complex reveals unusual tetrameric architecture and provides insights into dolichol synthesis mechanism and functional consequences of disease-associated hcis-PT mutations.
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