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Shieh JT, Tintos-Hernandez JA, Murali CN, Penon-Portmann M, Flores-Mendez M, Santana A, Bulos JA, Du K, Dupuis L, Damseh N, Mendoza-Londoño R, Berera C, Lee JC, Phillips JJ, Alves CAPF, Dmochowski IJ, Ortiz-González XR. Heterozygous nonsense variants in the ferritin heavy-chain gene FTH1 cause a neuroferritinopathy. HGG Adv 2023; 4:100236. [PMID: 37660254 PMCID: PMC10510067 DOI: 10.1016/j.xhgg.2023.100236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/04/2023] Open
Abstract
Ferritin, the iron-storage protein, is composed of light- and heavy-chain subunits, encoded by FTL and FTH1, respectively. Heterozygous variants in FTL cause hereditary neuroferritinopathy, a type of neurodegeneration with brain iron accumulation (NBIA). Variants in FTH1 have not been previously associated with neurologic disease. We describe the clinical, neuroimaging, and neuropathology findings of five unrelated pediatric patients with de novo heterozygous FTH1 variants. Children presented with developmental delay, epilepsy, and progressive neurologic decline. Nonsense FTH1 variants were identified using whole-exome sequencing, with a recurrent variant (p.Phe171∗) identified in four unrelated individuals. Neuroimaging revealed diffuse volume loss, features of pontocerebellar hypoplasia, and iron accumulation in the basal ganglia. Neuropathology demonstrated widespread ferritin inclusions in the brain. Patient-derived fibroblasts were assayed for ferritin expression, susceptibility to iron accumulation, and oxidative stress. Variant FTH1 mRNA transcripts escape nonsense-mediated decay (NMD), and fibroblasts show elevated ferritin protein levels, markers of oxidative stress, and increased susceptibility to iron accumulation. C-terminal variants in FTH1 truncate ferritin's E helix, altering the 4-fold symmetric pores of the heteropolymer, and likely diminish iron-storage capacity. FTH1 pathogenic variants appear to act by a dominant, toxic gain-of-function mechanism. The data support the conclusion that truncating variants in the last exon of FTH1 cause a disorder in the spectrum of NBIA. Targeted knockdown of mutant FTH1 transcript with antisense oligonucleotides rescues cellular phenotypes and suggests a potential therapeutic strategy for this pediatric neurodegenerative disorder.
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Affiliation(s)
- Joseph T Shieh
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143, USA.
| | - Jesus A Tintos-Hernandez
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Chaya N Murali
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Monica Penon-Portmann
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143, USA
| | - Marco Flores-Mendez
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Adrian Santana
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Joshua A Bulos
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kang Du
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lucie Dupuis
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - Nadirah Damseh
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - Roberto Mendoza-Londoño
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - Camilla Berera
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143, USA
| | - Julieann C Lee
- Division of Neuropathology, Department of Pathology, University of California San Francisco, San Francisco, CA 94143, USA
| | - Joanna J Phillips
- Division of Neuropathology, Department of Pathology, University of California San Francisco, San Francisco, CA 94143, USA; Department of Neurological Surgery, University of California San Francisco, San Francisco, CA 94143, USA
| | - César A P F Alves
- Division of Neuroradiology, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Ivan J Dmochowski
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Xilma R Ortiz-González
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Epilepsy Neurogenetics Initiative (ENGIN), The Children's Hospital of Philadelphia and Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Shieh JT, Tintos-Hernández JA, Murali CN, Penon-Portmann M, Flores-Mendez M, Santana A, Bulos JA, Du K, Dupuis L, Damseh N, Mendoza-Londoño R, Berera C, Lee JC, Phillips JJ, Alves CAPF, Dmochowski IJ, Ortiz-González XR. Heterozygous Nonsense Variants in the Ferritin Heavy Chain Gene FTH1 Cause a Novel Pediatric Neuroferritinopathy. medRxiv 2023:2023.01.30.23285099. [PMID: 36778397 PMCID: PMC9915813 DOI: 10.1101/2023.01.30.23285099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ferritin, the iron storage protein, is composed of light and heavy chain subunits, encoded by FTL and FTH1 , respectively. Heterozygous variants in FTL cause hereditary neuroferritinopathy, a type of neurodegeneration with brain iron accumulation (NBIA). Variants in FTH1 have not been previously associated with neurologic disease. We describe the clinical, neuroimaging, and neuropathology findings of five unrelated pediatric patients with de novo heterozygous FTH1 variants. Children presented with developmental delay, epilepsy, and progressive neurologic decline. Nonsense FTH1 variants were identified using whole exome sequencing, with a recurrent de novo variant (p.F171*) identified in three unrelated individuals. Neuroimaging revealed diffuse volume loss, features of pontocerebellar hypoplasia and iron accumulation in the basal ganglia. Neuropathology demonstrated widespread ferritin inclusions in the brain. Patient-derived fibroblasts were assayed for ferritin expression, susceptibility to iron accumulation, and oxidative stress. Variant FTH1 mRNA transcripts escape nonsense-mediated decay (NMD), and fibroblasts show elevated ferritin protein levels, markers of oxidative stress, and increased susceptibility to iron accumulation. C-terminus variants in FTH1 truncate ferritin's E-helix, altering the four-fold symmetric pores of the heteropolymer and likely diminish iron-storage capacity. FTH1 pathogenic variants appear to act by a dominant, toxic gain-of-function mechanism. The data support the conclusion that truncating variants in the last exon of FTH1 cause a novel disorder in the spectrum of NBIA. Targeted knock-down of mutant FTH1 transcript with antisense oligonucleotides rescues cellular phenotypes and suggests a potential therapeutic strategy for this novel pediatric neurodegenerative disorder.
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Affiliation(s)
- Joseph T Shieh
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, CA, 94143
- These authors contributed equally to this work
| | - Jesus A Tintos-Hernández
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104
- These authors contributed equally to this work
| | - Chaya N. Murali
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
| | - Monica Penon-Portmann
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, CA, 94143
| | - Marco Flores-Mendez
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104
| | - Adrian Santana
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104
| | - Joshua A. Bulos
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
| | - Kang Du
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
| | - Lucie Dupuis
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Canada
| | - Nadirah Damseh
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Canada
| | - Roberto Mendoza-Londoño
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Canada
| | - Camilla Berera
- Institute for Human Genetics and Department of Pediatrics, University of California San Francisco, CA, 94143
| | - Julieann C Lee
- Division of Neuropathology, Department of Pathology, University of California San Francisco, CA, 94143
| | - Joanna J Phillips
- Division of Neuropathology, Department of Pathology, University of California San Francisco, CA, 94143
- Department of Neurological Surgery, University of California San Francisco, CA, 94143
| | - César A P F Alves
- Division of Neuroradiology, Department of Pediatrics, The Children’s Hospital of Philadelphia
| | - Ivan J Dmochowski
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
| | - Xilma R Ortiz-González
- Division of Neurology and Center for Mitochondrial and Epigenomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104
- Epilepsy Neurogenetics Initiative (ENGIN), The Children’s Hospital of Philadelphia and Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104
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