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Dwarfism Miniature Horse Type
| Acronym: | DMHT |
| Gene: | ACAN D1, D2, D3*, D4 |
| Mutation: | c.245del, g.95284530C>T, c.1513G>C, c.7633_7653del |
| Inheritance: | Autosomal Recessive |
| Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Dwarfism Miniature horse type is an inherited growth disease that affects the Miniature horse breed. Miniature horses with dwarfism have severely shortened stature, bowed forelegs, shortened neck and limbs relative to overall body size, compressed faces with large bulging eye sockets, and low nasal bridge. Sometimes they can have cleft palate and protruding tongue, as well as a large abdominal hernia. Dwarfism Miniature horse type is caused by a genetic mutation in the aggrecan (ACAN) gene responsible for the proper functioning of the articular cartilage. Four different mutations (D1, D2, D3*, D4) in the ACAN gene cause this disease – two deletions and two missense mutations, all responsible for abnormalities in growth and development.
Dwarfism Miniature horse type is inherited as an autosomal recessive disease, meaning that two copies of the gene with the mutation are needed for a horse to be affected. Different combinations of the four mutations cause different clinical signs and severity of the disease. This type of dwarfism affects only the Miniature horse breed. The disease is incurable, but early detection by genetic testing can help find the right diagnosis, as well as in the prevention of further breeding by a selection of mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Andrade, D. G. A., Basso, R. M., Castiglioni, M. C. R., Silva, J. P., Machado, V. M. V., Laufer-Amorim, R., … Oliveira-Filho, J. P. (2020). Description of the D4/D4 genotype in Miniature horses with dwarfism. Journal of Veterinary Diagnostic Investigation, 104063871989816. doi:10.1177/1040638719898164
Eberth, J. E., Graves, K. T., MacLeod, J. N., & Bailey, E. (2018). Multiple alleles of ACAN associated with chondrodysplastic dwarfism in Miniature horses. Animal Genetics. doi:10.1111/age.12682