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Jiang A, You L, Handley RR, Hawkins V, Reid SJ, Jacobsen JC, Patassini S, Rudiger SR, Mclaughlan CJ, Kelly JM, Verma PJ, Bawden CS, Gusella JF, MacDonald ME, Waldvogel HJ, Faull RLM, Lehnert K, Snell RG. Single nuclei RNA-seq reveals a medium spiny neuron glutamate excitotoxicity signature prior to the onset of neuronal death in an ovine Huntington's disease model. Hum Mol Genet 2024:ddae087. [PMID: 38776957 DOI: 10.1093/hmg/ddae087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/11/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024] Open
Abstract
Huntington's disease (HD) is a neurodegenerative genetic disorder caused by an expansion in the CAG repeat tract of the huntingtin (HTT) gene resulting in behavioural, cognitive, and motor defects. Current knowledge of disease pathogenesis remains incomplete, and no disease course-modifying interventions are in clinical use. We have previously reported the development and characterisation of the OVT73 transgenic sheep model of HD. The 73 polyglutamine repeat is somatically stable and therefore likely captures a prodromal phase of the disease with an absence of motor symptomatology even at 5-years of age and no detectable striatal cell loss. To better understand the disease-initiating events we have undertaken a single nuclei transcriptome study of the striatum of an extensively studied cohort of 5-year-old OVT73 HD sheep and age matched wild-type controls. We have identified transcriptional upregulation of genes encoding N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors in medium spiny neurons, the cell type preferentially lost early in HD. Further, we observed an upregulation of astrocytic glutamate uptake transporters and medium spiny neuron GABAA receptors, which may maintain glutamate homeostasis. Taken together, these observations support the glutamate excitotoxicity hypothesis as an early neurodegeneration cascade-initiating process but the threshold of toxicity may be regulated by several protective mechanisms. Addressing this biochemical defect early may prevent neuronal loss and avoid the more complex secondary consequences precipitated by cell death.
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Affiliation(s)
- Andrew Jiang
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Linya You
- Department of Human Anatomy & Histoembryology, School of Basic Medical Sciences, Fudan University, 131 Dong'an Road, Shanghai 200032, China
- Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention of Shanghai, 130 Dong'an Road, Shanghai 200032, China
| | - Renee R Handley
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Victoria Hawkins
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Suzanne J Reid
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Jessie C Jacobsen
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Stefano Patassini
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Skye R Rudiger
- Molecular Biology and Reproductive Technology Laboratories, South Australian Research and Development Institute, 129 Holland Road, Adelaide, SA 5350, Australia
| | - Clive J Mclaughlan
- Molecular Biology and Reproductive Technology Laboratories, South Australian Research and Development Institute, 129 Holland Road, Adelaide, SA 5350, Australia
| | - Jennifer M Kelly
- Molecular Biology and Reproductive Technology Laboratories, South Australian Research and Development Institute, 129 Holland Road, Adelaide, SA 5350, Australia
| | - Paul J Verma
- Aquatic and Livestock Sciences, South Australian Research and Development Institute, 129 Holland Road, Adelaide, SA 5350, Australia
| | - C Simon Bawden
- Molecular Biology and Reproductive Technology Laboratories, South Australian Research and Development Institute, 129 Holland Road, Adelaide, SA 5350, Australia
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, United States
- Department of Genetics, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, United States
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, United States
- Department of Neurology, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, United States
| | - Henry J Waldvogel
- Department of Anatomy and Medical Imaging, Centre for Brain Research, Faculty of Medical and Health Science, The University of Auckland, 85 Park Road, Auckland 1023, New Zealand
| | - Richard L M Faull
- Department of Anatomy and Medical Imaging, Centre for Brain Research, Faculty of Medical and Health Science, The University of Auckland, 85 Park Road, Auckland 1023, New Zealand
| | - Klaus Lehnert
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
| | - Russell G Snell
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, 3 Symonds Street, Auckland 1010, New Zealand
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Ekwudo MN, Gubert C, Hannan AJ. The microbiota-gut-brain axis in Huntington's disease: pathogenic mechanisms and therapeutic targets. FEBS J 2024. [PMID: 38426291 DOI: 10.1111/febs.17102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/08/2024] [Accepted: 02/14/2024] [Indexed: 03/02/2024]
Abstract
Huntington's disease (HD) is a currently incurable neurogenerative disorder and is typically characterized by progressive movement disorder (including chorea), cognitive deficits (culminating in dementia), psychiatric abnormalities (the most common of which is depression), and peripheral symptoms (including gastrointestinal dysfunction). There are currently no approved disease-modifying therapies available for HD, with death usually occurring approximately 10-25 years after onset, but some therapies hold promising potential. HD subjects are often burdened by chronic diarrhea, constipation, esophageal and gastric inflammation, and a susceptibility to diabetes. Our understanding of the microbiota-gut-brain axis in HD is in its infancy and growing evidence from preclinical and clinical studies suggests a role of gut microbial population imbalance (gut dysbiosis) in HD pathophysiology. The gut and the brain can communicate through the enteric nervous system, immune system, vagus nerve, and microbiota-derived-metabolites including short-chain fatty acids, bile acids, and branched-chain amino acids. This review summarizes supporting evidence demonstrating the alterations in bacterial and fungal composition that may be associated with HD. We focus on mechanisms through which gut dysbiosis may compromise brain and gut health, thus triggering neuroinflammatory responses, and further highlight outcomes of attempts to modulate the gut microbiota as promising therapeutic strategies for HD. Ultimately, we discuss the dearth of data and the need for more longitudinal and translational studies in this nascent field. We suggest future directions to improve our understanding of the association between gut microbes and the pathogenesis of HD, and other 'brain and body disorders'.
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Affiliation(s)
- Millicent N Ekwudo
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Carolina Gubert
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Anthony J Hannan
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Australia
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Handley RR, Reid SJ, Burch Z, Jacobsen JC, Gillis T, Correia K, Rudiger SR, McLaughlin CJ, Bawden CS, MacDonald ME, Wheeler VC, Snell RG. Somatic CAG Repeat Stability in a Transgenic Sheep Model of Huntington's Disease. J Huntingtons Dis 2024; 13:33-40. [PMID: 38393920 DOI: 10.3233/jhd-231516] [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] [Indexed: 02/25/2024]
Abstract
Somatic instability of the huntingtin (HTT) CAG repeat mutation modifies age-at-onset of Huntington's disease (HD). Understanding the mechanism and pathogenic consequences of instability may reveal therapeutic targets. Using small-pool PCR we analyzed CAG instability in the OVT73 sheep model which expresses a full-length human cDNA HTT transgene. Analyses of five- and ten-year old sheep revealed the transgene (CAG)69 repeat was remarkably stable in liver, striatum, and other brain tissues. As OVT73 sheep at ten years old have minimal cell death and behavioral changes, our findings support instability of the HTT expanded-CAG repeat as being required for the progression of HD.
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Affiliation(s)
- Renee R Handley
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Suzanne J Reid
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Zoe Burch
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Jessie C Jacobsen
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Tammy Gillis
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Kevin Correia
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Skye R Rudiger
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - Clive J McLaughlin
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - C Simon Bawden
- Molecular Biology and Reproductive Technology, Laboratories, South Australian Research and Development Institute, Adelaide, SA, Australia
| | - Marcy E MacDonald
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Vanessa C Wheeler
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Russell G Snell
- Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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Murray SJ, Mitchell NL. The Translational Benefits of Sheep as Large Animal Models of Human Neurological Disorders. Front Vet Sci 2022; 9:831838. [PMID: 35242840 PMCID: PMC8886239 DOI: 10.3389/fvets.2022.831838] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 01/21/2022] [Indexed: 12/15/2022] Open
Abstract
The past two decades have seen a considerable rise in the use of sheep to model human neurological disorders. While each animal model has its merits, sheep have many advantages over small animal models when it comes to studies on the brain. In particular, sheep have brains more comparable in size and structure to the human brain. They also have much longer life spans and are docile animals, making them useful for a wide range of in vivo studies. Sheep are amenable to regular blood and cerebrospinal fluid sampling which aids in biomarker discovery and monitoring of treatment efficacy. Several neurological diseases have been found to occur naturally in sheep, however sheep can also be genetically engineered or experimentally manipulated to recapitulate disease or injury. Many of these types of sheep models are currently being used for pre-clinical therapeutic trials, particularly gene therapy, with studies from several models culminating in potential treatments moving into clinical trials. This review will provide an overview of the benefits of using sheep to model neurological conditions, and highlight naturally occurring and experimentally induced sheep models that have demonstrated translational validity.
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Affiliation(s)
- Samantha J Murray
- Faculty of Agriculture and Life Sciences, Lincoln University, Canterbury, New Zealand
| | - Nadia L Mitchell
- Faculty of Agriculture and Life Sciences, Lincoln University, Canterbury, New Zealand
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