OMIA:002846-9796 : Spinocerebellar ataxia, juvenile, FDXR-related in Equus caballus (domestic horse) |
Categories: Nervous system phene
Links to possible relevant human trait(s) and/or gene(s) in OMIM: 103270 (gene) , 620887 (trait)
Single-gene trait/disorder: yes
Mode of inheritance: Autosomal recessive
Disease-related: yes
Key variant known: yes
Year key variant first reported: 2025
Species summary: Willis et al. (2024) report a novel lethal spinocerebellar ataxia in 12 related young Quarter Horses "that is etiologically distinct from other clinically similar neurological disorders."
Species-specific name: Equine Juvenile Spinocerebellar Ataxia; EJSCA
Species-specific symbol: EJSCA
Molecular basis: Brown et al. (2025) reported in a conference abstract reduced FDXR expression in horses with equine juvenile spinocerebellar ataxia and propose that an intronic G>C SNP in intron 2 of FDXR is the likely causal variant (omia.variant:1914). The variant introduces a new splice site, resulting in a cryptic exon which is predicted to result in nonsense-mediated mRNA decay. Details of the postition of the variant were not provided in the abstract but were later published as chr11:6973334 G>C, FDXR-203 c.177 + 1778G > C (Brown et al. 2026).
Clinical features: Brown et al. (2026): "Affected [Quarter Horse] foals [appear healthy at birth and] display a progressive proprioceptive ataxia by 1–5 weeks of age, leading to recumbency and necessitating euthanasia. ... Clinicopathologic findings included elevated gamma-glutamyl transferase (GGT) and hyperglycemia on biochemical profiles, with normal muscle enzymes."
Pathology: Brown et al. (2026): "Postmortem evaluation identified dilated myelin sheaths with digestion chambers throughout the entire spinal cord but most severe in the dorsal spinocerebellar tracts of the cervicothoracic region."
Breed:
Quarter Horse (Horse) (VBO_0001057).
Breeds in which the phene or likely causal variants have been documented. If a likely causal variant has been documented, see variant-specific breed information in the variant table. (Breed information may be incomplete).
Associated gene:
| Symbol | Description | Species | Chr | Location | OMIA gene details page | Other Links |
|---|---|---|---|---|---|---|
| FDXR | ferredoxin reductase | Equus caballus | 11 | NC_091694.1 (6987670..6998005) | FDXR | Ensembl, NCBI gene |
Variants
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WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.
Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.
| OMIA Variant ID | Breed(s) | Variant Phenotype | Gene | Allele | Variant Type | Variant Effect | Source of Genetic Variant | AVCG Pathogenicity Classification* | Reference Sequence | Chr. | g. or m. | c. or n. | p. | Verbal Description | EVA ID | Year Published | PubMed ID(s) | Acknowledgements |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1914 | Quarter Horse (Horse) | Spinocerebellar ataxia, juvenile | FDXR | substitution | splicing | Naturally occurring variant | Not currently evaluated | EquCab3.0 | 11 | NC_009154.3:g.6973334G>C | XM_023652064.1:c.177+1778G>C | eighth base pair of a cryptic exon identified in spinal cord tissue of affected horses | 2026 | 42160398 |
* Variant pathogenicity for single-gene diseases as evaluated according to the Animal Variant Classification Guidelines (AVCG) by the Variant Pathogenicity Working Group of the International Society of Animal Genetics (ISAG) Animal Genetic Testing Standardization (AGTS) Standing Committee: P = pathogenic, LP = likely pathogenic, VUS = variant of unknown significance, LB = likely benign, B = benign. For more information (including details on the classification of each variant) see LINKS.
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Cite this entry
Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2026). OMIA:002846-9796: Online Mendelian Inheritance in Animals (OMIA) [dataset]. https://omia.org/. https://doi.org/10.25910/2AMR-PV70
References
Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
| 2026 | Brown, B.N., Dahlgren, A.R., Ghosh, S., Durbin-Johnson, B., Willis, A., Olivas, C., York, D., Grahn, R., Bellone, R.R., Cortopassi, G.A., Miller, A.D., Brown, C.T., Woolard, K., Finno, C.J. : |
| An intronic variant in ferredoxin reductase (FDXR) creates a cryptic exon in Quarter Horses with equine juvenile spinocerebellar ataxia. PLoS Genet 22:e1012158, 2026. Pubmed reference: 42160398. DOI: 10.1371/journal.pgen.1012158. | |
| 2025 | Brown, B.N., Ghosh, S., Miller, A., Cortopassi, G.A., Grahn, R.A., Bellone, R.R., Finno, C.J. : |
| Identification of a cryptic exon in FDXR associated with equine juvenile spinocerebellar ataxia in Quarter Horses. Journal of Equine Veterinary Science 148:137, 2025. DOI: 10.1016/j.jevs.2025.105561. | |
| 2024 | Willis, A.T., Dahlgren, A.R., Woolard, K.D., Ghosh, S., Donnelly, C.G., de la Concha-Bermejillo, A., Pacheco, A., Watson, K.D., Berryhill, E., Aleman, M., Wensley, F., Humphreys, S., Whitehead, A.E., Goldsmith, D., Chesen, B., Ragsdale, J., Tompkins, J.E., Nash, R., Plunkett, A.H., Qualls, H.J., Rodriguez, K., Hochanadel, D., Miller, A.D., Finno, C.J. : |
| Clinicopathological and pedigree investigation of a novel spinocerebellar neurological disease in juvenile Quarter Horses in North America. J Vet Intern Med 38:1808-1814, 2024. Pubmed reference: 38669583. DOI: 10.1111/jvim.17049. |
Edit History
- Created by Imke Tammen on 28 Apr 2024
- Changed by Imke Tammen on 30 Mar 2026
- Changed by Imke Tammen on 22 Jul 2026