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Young AE, Finno CJ. Current insights into equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy. Vet J 2024; 305:106129. [PMID: 38734404 DOI: 10.1016/j.tvjl.2024.106129] [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: 03/04/2024] [Revised: 05/06/2024] [Accepted: 05/07/2024] [Indexed: 05/13/2024]
Abstract
Equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM) is an inherited neurodegenerative disease associated with vitamin E deficiency in the first year of life. It is the second most common cause of spinal ataxia in horses euthanized for neurologic disease. Equine NAD/EDM is characterized by neurologic signs including a symmetric proprioceptive ataxia (> grade 2/5) and a wide-base stance at rest. There are currently no antemortem tests for eNAD/EDM in any breed. Conclusive diagnosis requires postmortem histologic evaluation of the brainstem and spinal cord at necropsy. Research studies on antemortem biomarkers and genetic testing are ongoing. The development of a genetic test for eNAD/EDM would have widespread impact, even if it were breed specific. Currently, the best approach to eNAD/EDM is to focus on preventing cases by providing pregnant mares and foals with access to pasture. Alternatively, dams' diets can be supplemented with high doses of water-soluble RRR-α-tocopherol during the last trimester of gestation, with continued supplementation of foals through the first two years of life. It is important to measure horses' baseline serum vitamin E levels prior to supplementing. While considered generally safe, oversupplementation of vitamin E is possible and can lead to coagulopathies.
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Affiliation(s)
- Amy E Young
- Center for Equine Health, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Carrie J Finno
- Center for Equine Health, School of Veterinary Medicine, University of California, Davis, CA, USA; Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA.
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Tanaka M, Fujikawa R, Sekiguchi T, Hernandez J, Johnson OT, Tanaka D, Kumafuji K, Serikawa T, Hoang Trung H, Hattori K, Mashimo T, Kuwamura M, Gestwicki JE, Kuramoto T. A missense mutation in the Hspa8 gene encoding heat shock cognate protein 70 causes neuroaxonal dystrophy in rats. Front Neurosci 2024; 18:1263724. [PMID: 38384479 PMCID: PMC10880117 DOI: 10.3389/fnins.2024.1263724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 01/16/2024] [Indexed: 02/23/2024] Open
Abstract
Neuroaxonal dystrophy (NAD) is a neurodegenerative disease characterized by spheroid (swollen axon) formation in the nervous system. In the present study, we focused on a newly established autosomal recessive mutant strain of F344-kk/kk rats with hind limb gait abnormalities and ataxia from a young age. Histopathologically, a number of axonal spheroids were observed throughout the central nervous system, including the spinal cord (mainly in the dorsal cord), brain stem, and cerebellum in F344-kk/kk rats. Transmission electron microscopic observation of the spinal cord revealed accumulation of electron-dense bodies, degenerated abnormal mitochondria, as well as membranous or tubular structures in the axonal spheroids. Based on these neuropathological findings, F344-kk/kk rats were diagnosed with NAD. By a positional cloning approach, we identified a missense mutation (V95E) in the Hspa8 (heat shock protein family A (Hsp70) member 8) gene located on chromosome 8 of the F344-kk/kk rat genome. Furthermore, we developed the Hspa8 knock-in (KI) rats with the V95E mutation using the CRISPR-Cas system. Homozygous Hspa8-KI rats exhibited ataxia and axonal spheroids similar to those of F344-kk/kk rats. The V95E mutant HSC70 protein exhibited the significant but modest decrease in the maximum hydrolysis rate of ATPase when stimulated by co-chaperons DnaJB4 and BAG1 in vitro, which suggests the functional deficit in the V95E HSC70. Together, our findings provide the first evidence that the genetic alteration of the Hspa8 gene caused NAD in mammals.
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Affiliation(s)
- Miyuu Tanaka
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
- Laboratory of Veterinary Pathology, Graduate School of Veterinary Science, Osaka Metropolitan University, Izumisano, Osaka, Japan
| | - Ryoko Fujikawa
- Laboratory of Veterinary Pathology, Graduate School of Veterinary Science, Osaka Metropolitan University, Izumisano, Osaka, Japan
| | - Takahiro Sekiguchi
- Laboratory of Veterinary Pathology, Graduate School of Veterinary Science, Osaka Metropolitan University, Izumisano, Osaka, Japan
| | - Jason Hernandez
- Department of Pharmaceutical Chemistry and the Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, United States
| | - Oleta T. Johnson
- Department of Pharmaceutical Chemistry and the Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, United States
| | - Daisuke Tanaka
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Kenta Kumafuji
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Tadao Serikawa
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Hieu Hoang Trung
- Department of Animal Science, Faculty of Agriculture, Tokyo University of Agriculture, Atsugi, Kanagawa, Japan
| | - Kosuke Hattori
- Division of Animal Genetics, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, Japan
| | - Tomoji Mashimo
- Division of Animal Genetics, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, Japan
| | - Mitsuru Kuwamura
- Laboratory of Veterinary Pathology, Graduate School of Veterinary Science, Osaka Metropolitan University, Izumisano, Osaka, Japan
| | - Jason E. Gestwicki
- Department of Pharmaceutical Chemistry and the Institute for Neurodegenerative Diseases, University of California, San Francisco, San Francisco, CA, United States
| | - Takashi Kuramoto
- Institute of Laboratory Animals, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
- Department of Animal Science, Faculty of Agriculture, Tokyo University of Agriculture, Atsugi, Kanagawa, Japan
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Finno CJ, Johnson AL. Equine Neuroaxonal Dystrophy and Degenerative Myeloencephalopathy. Vet Clin North Am Equine Pract 2022; 38:213-224. [PMID: 35811203 DOI: 10.1016/j.cveq.2022.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Neuroaxonal degenerative disease in the horse is termed equine neuroaxonal dystrophy (eNAD), when pathologic lesions are localized to the brainstem and equine degenerative myeloencephalopathy (EDM) and degenerative changes extend throughout the spinal cord. Both pathologic conditions result in identical clinical disease, most commonly characterized by the insidious onset of ataxia during early development. However, later onset of clinical signs and additional clinical features, such as behavior changes, is also observed. A definitive diagnosis of eNAD/EDM requires histologic evaluation of the caudal medulla and cervicothoracic spinal cord. Strong evidence has suggested that eNAD/EDM is an inherited disorder and there seems to be a role for vitamin E acting as an environmental modifier to determine the overall severity of the phenotype of horses affected with eNAD/EDM.
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Affiliation(s)
- Carrie J Finno
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA.
| | - Amy L Johnson
- Department of Clinical Studies, University of Pennsylvania School of Veterinary Medicine- New Bolton Center, 382 West Street Road, Kennett Square, PA 19348, USA
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Abstract
Neurologic disease in horses can be particularly challenging to diagnose and treat. These diseases can result in economic losses, emotional distress to owners, and injury to the horse or handlers. To date, there are 5 neurologic diseases caused by known genetic mutations and several more are suspected to be heritable: lethal white foal syndrome, lavender foal syndrome, cerebellar abiotrophy, occipitoatlantoaxial malformation, and Friesian hydrocephalus. Genetic testing allows owners, breeders, and veterinarians to make informed decisions when selecting dams and sires for breeding or deciding the treatment or prognosis of a neurologic animal.
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Affiliation(s)
- Lisa Edwards
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA
| | - Carrie J Finno
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA.
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