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Zhu Y, Cho K, Lacin H, Zhu Y, DiPaola JT, Wilson BA, Patti GJ, Skeath JB. Loss of dihydroceramide desaturase drives neurodegeneration by disrupting endoplasmic reticulum and lipid droplet homeostasis in glial cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.01.573836. [PMID: 38260379 PMCID: PMC10802327 DOI: 10.1101/2024.01.01.573836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Dihydroceramide desaturases convert dihydroceramides to ceramides, the precursors of all complex sphingolipids. Reduction of DEGS1 dihydroceramide desaturase function causes pediatric neurodegenerative disorder hypomyelinating leukodystrophy-18 (HLD-18). We discovered that infertile crescent (ifc), the Drosophila DEGS1 homolog, is expressed primarily in glial cells to promote CNS development by guarding against neurodegeneration. Loss of ifc causes massive dihydroceramide accumulation and severe morphological defects in cortex glia, including endoplasmic reticulum (ER) expansion, failure of neuronal ensheathment, and lipid droplet depletion. RNAi knockdown of the upstream ceramide synthase schlank in glia of ifc mutants rescues ER expansion, suggesting dihydroceramide accumulation in the ER drives this phenotype. RNAi knockdown of ifc in glia but not neurons drives neuronal cell death, suggesting that ifc function in glia promotes neuronal survival. Our work identifies glia as the primary site of disease progression in HLD-18 and may inform on juvenile forms of ALS, which also feature elevated dihydroceramide levels.
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Affiliation(s)
- Yuqing Zhu
- Department of Genetics, Washington University School of Medicine, 4523 Clayton Avenue, St. Louis, MO 63110, USA
| | - Kevin Cho
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
- Center for Mass Spectrometry and Metabolic Tracing, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
| | - Haluk Lacin
- Division of Biological and Biomedical Systems, University of Missouri-Kansas City, Kansas City, MO 64110, USA
| | - Yi Zhu
- Department of Genetics, Washington University School of Medicine, 4523 Clayton Avenue, St. Louis, MO 63110, USA
| | - Jose T DiPaola
- Department of Genetics, Washington University School of Medicine, 4523 Clayton Avenue, St. Louis, MO 63110, USA
| | - Beth A Wilson
- Department of Genetics, Washington University School of Medicine, 4523 Clayton Avenue, St. Louis, MO 63110, USA
| | - Gary J Patti
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
- Center for Mass Spectrometry and Metabolic Tracing, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
| | - James B Skeath
- Department of Genetics, Washington University School of Medicine, 4523 Clayton Avenue, St. Louis, MO 63110, USA
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Mohassel P, Abdullah M, Eichler FS, Dunn TM. Serine Palmitoyltransferase (SPT)-related Neurodegenerative and Neurodevelopmental Disorders. J Neuromuscul Dis 2024:JND240014. [PMID: 38788085 DOI: 10.3233/jnd-240014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2024]
Abstract
Motor neuron diseases and peripheral neuropathies are heterogeneous groups of neurodegenerative disorders that manifest with distinct symptoms due to progressive dysfunction or loss of specific neuronal subpopulations during different stages of development. A few monogenic, neurodegenerative diseases associated with primary metabolic disruptions of sphingolipid biosynthesis have been recently discovered. Sphingolipids are a subclass of lipids that form critical building blocks of all cellular and subcellular organelle membranes including the membrane components of the nervous system cells. They are especially abundant within the lipid portion of myelin. In this review, we will focus on our current understanding of disease phenotypes in three monogenic, neuromuscular diseases associated with pathogenic variants in components of serine palmitoyltransferase, the first step in sphingolipid biosynthesis. These include hereditary sensory and autonomic neuropathy type 1 (HSAN1), a sensory predominant peripheral neuropathy, and two neurodegenerative disorders: juvenile amyotrophic lateral sclerosis affecting the upper and lower motor neurons with sparing of sensory neurons, and a complicated form of hereditary spastic paraplegia with selective involvement of the upper motor neurons and more broad CNS neurodegeneration. We will also review our current understanding of disease pathomechanisms, therapeutic approaches, and the unanswered questions to explore in future studies.
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Affiliation(s)
- Payam Mohassel
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Meher Abdullah
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Florian S Eichler
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Teresa M Dunn
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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Dubot P, Sabourdy F, Levade T. Human genetic defects of sphingolipid synthesis. J Inherit Metab Dis 2024. [PMID: 38706107 DOI: 10.1002/jimd.12745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 04/11/2024] [Accepted: 04/15/2024] [Indexed: 05/07/2024]
Abstract
Sphingolipids are ubiquitous lipids, present in the membranes of all cell types, the stratum corneum and the circulating lipoproteins. Autosomal recessive as well as dominant diseases due to disturbed sphingolipid biosynthesis have been identified, including defects in the synthesis of ceramides, sphingomyelins and glycosphingolipids. In many instances, these gene variants result in the loss of catalytic function of the mutated enzymes. Additional gene defects implicate the subcellular localization of the sphingolipid-synthesizing enzyme, the regulation of its activity, or even the function of a sphingolipid-transporter protein. The resulting metabolic alterations lead to two major, non-exclusive types of clinical manifestations: a neurological disease, more or less rapidly progressive, associated or not with intellectual disability, and an ichthyotic-type skin disorder. These phenotypes highlight the critical importance of sphingolipids in brain and skin development and homeostasis. The present article reviews the clinical symptoms, genetic and biochemical alterations, pathophysiological mechanisms and therapeutic options of this relatively novel group of metabolic diseases.
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Affiliation(s)
- Patricia Dubot
- Unité Mixte de Recherche INSERM 1037, CNRS 5071, Université Toulouse III-Paul Sabatier, Centre de Recherches en Cancérologie de Toulouse (CRCT), Toulouse, France
- Laboratoire de Biochimie, Institut Fédératif de Biologie, CHU Purpan, Toulouse, France
- Centre de Recherches, CHU Sainte-Justine, Université de Montréal, Montréal, Canada
| | - Frédérique Sabourdy
- Unité Mixte de Recherche INSERM 1037, CNRS 5071, Université Toulouse III-Paul Sabatier, Centre de Recherches en Cancérologie de Toulouse (CRCT), Toulouse, France
- Laboratoire de Biochimie, Institut Fédératif de Biologie, CHU Purpan, Toulouse, France
| | - Thierry Levade
- Unité Mixte de Recherche INSERM 1037, CNRS 5071, Université Toulouse III-Paul Sabatier, Centre de Recherches en Cancérologie de Toulouse (CRCT), Toulouse, France
- Laboratoire de Biochimie, Institut Fédératif de Biologie, CHU Purpan, Toulouse, France
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Dohrn MF, Beijer D, Lone MA, Bayraktar E, Oflazer P, Orbach R, Donkervoort S, Foley AR, Rose A, Lyons M, Louie RJ, Gable K, Dunn T, Chen S, Danzi MC, Synofzik M, Bönnemann CG, Nazlı Başak A, Hornemann T, Zuchner S. Recurrent de-novo gain-of-function mutation in SPTLC2 confirms dysregulated sphingolipid production to cause juvenile amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry 2024; 95:201-205. [PMID: 38041684 PMCID: PMC10922288 DOI: 10.1136/jnnp-2023-332130] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 09/27/2023] [Indexed: 12/03/2023]
Abstract
BACKGROUND Amyotrophic lateral sclerosis (ALS) leads to paralysis and death by progressive degeneration of motor neurons. Recently, specific gain-of-function mutations in SPTLC1 were identified in patients with juvenile form of ALS. SPTLC2 encodes the second catalytic subunit of the serine-palmitoyltransferase (SPT) complex. METHODS We used the GENESIS platform to screen 700 ALS whole-genome and whole-exome data sets for variants in SPTLC2. The de-novo status was confirmed by Sanger sequencing. Sphingolipidomics was performed using liquid chromatography and high-resolution mass spectrometry. RESULTS Two unrelated patients presented with early-onset progressive proximal and distal muscle weakness, oral fasciculations, and pyramidal signs. Both patients carried the novel de-novo SPTLC2 mutation, c.203T>G, p.Met68Arg. This variant lies within a single short transmembrane domain of SPTLC2, suggesting that the mutation renders the SPT complex irresponsive to regulation through ORMDL3. Confirming this hypothesis, ceramide and complex sphingolipid levels were significantly increased in patient plasma. Accordingly, excessive sphingolipid production was shown in mutant-expressing human embryonic kindney (HEK) cells. CONCLUSIONS Specific gain-of-function mutations in both core subunits affect the homoeostatic control of SPT. SPTLC2 represents a new Mendelian ALS gene, highlighting a key role of dysregulated sphingolipid synthesis in the pathogenesis of juvenile ALS. Given the direct interaction of SPTLC1 and SPTLC2, this knowledge might open new therapeutic avenues for motor neuron diseases.
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Affiliation(s)
- Maike F Dohrn
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, USA
- Department of Neurology, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - Danique Beijer
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, USA
- Translational Genomics of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Museer A Lone
- Institute of Clinical Chemistry, University Hospital Zürich, Zürich, Switzerland
| | - Elif Bayraktar
- Koç University, School of Medicine, Translational Medicine Research Center- NDAL, Istanbul, Turkey
| | - Piraye Oflazer
- Koç University, School of Medicine, Department of Neurology, Istanbul, Turkey
| | - Rotem Orbach
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - A Reghan Foley
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - Aubrey Rose
- Greenwood Genetic Center Foundation, Greenwood, South Carolina, USA
| | - Michael Lyons
- Greenwood Genetic Center Foundation, Greenwood, South Carolina, USA
| | - Raymond J Louie
- Greenwood Genetic Center Foundation, Greenwood, South Carolina, USA
| | - Kenneth Gable
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, Maryland, USA
| | - Teresa Dunn
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, Maryland, USA
| | - Sitong Chen
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Matt C Danzi
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, USA
| | - Matthis Synofzik
- Translational Genomics of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases (DZNE), University of Tübingen, Tübingen, Germany
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institutes of Health, Bethesda, Maryland, USA
| | - A Nazlı Başak
- Koç University, School of Medicine, Translational Medicine Research Center- NDAL, Istanbul, Turkey
| | - Thorsten Hornemann
- Institute of Clinical Chemistry, University Hospital Zürich, Zürich, Switzerland
| | - Stephan Zuchner
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, Florida, USA
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Syeda SB, Lone MA, Mohassel P, Donkervoort S, Munot P, França MC, Galarza-Brito JE, Eckenweiler M, Asamoah A, Gable K, Majumdar A, Schumann A, Gupta SD, Lakhotia A, Shieh PB, Foley AR, Jackson KE, Chao KR, Winder TL, Catapano F, Feng L, Kirschner J, Muntoni F, Dunn TM, Hornemann T, Bönnemann CG. Recurrent de novo SPTLC2 variant causes childhood-onset amyotrophic lateral sclerosis (ALS) by excess sphingolipid synthesis. J Neurol Neurosurg Psychiatry 2024; 95:103-113. [PMID: 38041679 PMCID: PMC10850718 DOI: 10.1136/jnnp-2023-332132] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 09/27/2023] [Indexed: 12/03/2023]
Abstract
BACKGROUND Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the upper and lower motor neurons with varying ages of onset, progression and pathomechanisms. Monogenic childhood-onset ALS, although rare, forms an important subgroup of ALS. We recently reported specific SPTLC1 variants resulting in sphingolipid overproduction as a cause for juvenile ALS. Here, we report six patients from six independent families with a recurrent, de novo, heterozygous variant in SPTLC2 c.778G>A [p.Glu260Lys] manifesting with juvenile ALS. METHODS Clinical examination of the patients along with ancillary and genetic testing, followed by biochemical investigation of patients' blood and fibroblasts, was performed. RESULTS All patients presented with early-childhood-onset progressive weakness, with signs and symptoms of upper and lower motor neuron degeneration in multiple myotomes, without sensory neuropathy. These findings were supported on ancillary testing including nerve conduction studies and electromyography, muscle biopsies and muscle ultrasound studies. Biochemical investigations in plasma and fibroblasts showed elevated levels of ceramides and unrestrained de novo sphingolipid synthesis. Our studies indicate that SPTLC2 variant [c.778G>A, p.Glu260Lys] acts distinctly from hereditary sensory and autonomic neuropathy (HSAN)-causing SPTLC2 variants by causing excess canonical sphingolipid biosynthesis, similar to the recently reported SPTLC1 ALS associated pathogenic variants. Our studies also indicate that serine supplementation, which is a therapeutic in SPTLC1 and SPTCL2-associated HSAN, is expected to exacerbate the excess sphingolipid synthesis in serine palmitoyltransferase (SPT)-associated ALS. CONCLUSIONS SPTLC2 is the second SPT-associated gene that underlies monogenic, juvenile ALS and further establishes alterations of sphingolipid metabolism in motor neuron disease pathogenesis. Our findings also have important therapeutic implications: serine supplementation must be avoided in SPT-associated ALS, as it is expected to drive pathogenesis further.
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Affiliation(s)
- Safoora B Syeda
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Museer A Lone
- Institute of Clinical Chemistry, University Hospital Zürich, Zürich, Switzerland
| | - Payam Mohassel
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Pinki Munot
- NIHR Great Ormond Street Hospital Biomedical Research Centre, London, UK
| | - Marcondes C França
- Department of Neurology, University of Campinas, Campinas, Sao Paulo, Brazil
| | | | - Matthias Eckenweiler
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center, University of Freiburg, Freiburg, Germany
| | - Alexander Asamoah
- Norton Children's Medical Group, University of Louisville School of Medicine, Louisville, KY, USA
| | - Kenneth Gable
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, Maryland, USA
| | - Anirban Majumdar
- Department of Paediatric Neurology, Bristol Children's Hospital, Bristol, UK
| | - Anke Schumann
- Department of Paediatrics and Adolescent Medicine, Faculty of Medicine, Medical Centre, University of Freiburg, Baden-Württemberg, Germany
| | - Sita D Gupta
- Department of Biochemistry and Molecular Biology, Uniformed Services University, Bethesda, Maryland, USA
| | - Arpita Lakhotia
- Norton Children's Medical Group, University of Louisville School of Medicine, Louisville, KY, USA
- University of Louisville, Louisville, Kentucky, USA
| | - Perry B Shieh
- Department of Neurology and Pediatrics, University of California Los Angeles, Los Angeles, CA, USA
| | - A Reghan Foley
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | - Kelly E Jackson
- Norton Children's Medical Group, University of Louisville School of Medicine, Louisville, KY, USA
| | - Katherine R Chao
- Center for Mendelian Genomics, Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | | | - Francesco Catapano
- Dubowitz Neuromuscular Centre, CL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital, London, UK
| | - Lucy Feng
- Dubowitz Neuromuscular Centre, CL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital, London, UK
| | - Janbernd Kirschner
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center, University of Freiburg, Freiburg, Germany
| | - Francesco Muntoni
- NIHR Great Ormond Street Hospital Biomedical Research Centre, London, UK
- Dubowitz Neuromuscular Centre, CL Great Ormond Street Institute of Child Health and Great Ormond Street Hospital, London, UK
| | - Teresa M Dunn
- Department of Biochemistry and Molecular Biology, Uniformed Services University of Health Sciences, Bethesda, MD, USA
| | - Thorsten Hornemann
- Institute of Clinical Chemistry, University Hospital Zürich, Zürich, Switzerland
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
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