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Dwarfism Panel (ACAN + SA)

180,00 

→ Combo-Package testing ACAN and SA for Shetland Pony, Miniature Horses and related breeds.


Instructions for ordering:

  1. Enter the information of the first horse for which you want to order the test
  2. Add to cart
  3. Go to cart to check out, or
  4. Enter the information for a second horse
  5. For sample collection follow the instructions here.
  6. You can use this template to send in hair samples.
  7. Please also send the completed order form together with the samples.

For a breeder or veterinarian discount please contact us before ordering.

Any information you include here is optional, but will be included on the certificate of results (except “Additional Info”).

Enter the name of your animal
Enter your animal's date/year of birth
Enter the breed name
Enter the registration number if known
Enter the microchip number
Is there anything else you would like to tell us about your horse? Reason for testing, symptoms etc.?

ACAN Dwarfism/Chondrodysplasia

Abnormal cartilage growth leading to skeletal problems and dwarfism
General Information:

  • Four causative variants for ACAN dwarfism have been identified and validated so far: D1, D2, D3* and D4.
  • All variants show similar phenotypes and lead to dwarfism in Miniature Horses and Shetland ponies.
  • An affected pony may have two of the same, or two different variants. Any combination with D1 results in early spontaneous abortion of the affected foal (D1/D1, D1/D2, D1/D3*, D1/D4).
  • Other combinations show the phenotype described above. Symptoms may vary from mild to severe. Affected ponies are often euthanized because of poor quality of life.
  • Some combinations are very rare (D3*/D3*, D4/D4). The effects of these genotypes on the horse’s phenotype are yet unknown.
  • Originally five different variants have been reported to cause the ACAN dwarfism. The original D3 variant has been proven incorrect, and the fifth variant reported (Metzger et al. 2017) been named D3*. CAG tests for this corrected D3* variant.
  • Another form of dwarfism also results in health issues in Shetland ponies and Miniature Horses: Skeletal Atavism (SA, Del-dwarfism). It is possible for ponies to be carriers of both ACAN and SA.

Symptoms:

  • Globular head
  • Shortened torso/neck
  • Enlarged joints
  • Bowed forelegs
  • Underbite
  • Cleft palate (resulting in difficulties breathing)
  • Pain

Possible Genotypes:

Genotype: The horse is:
Effects:
N/N normal. The horse/pony has no copies of the mutations causative for ACAN dwarfism and therefore cannot pass it on to its offspring.
N/d a carrier. The horse/pony is a clinically normal carrier. The variant will be passed on to its offspring with a probability of 50%.
d/d affected. The variant will be passed on to all offspring. All offspring will be carriers (N/d). Any combination with the D1 variant will lead to early abortion of the affected foal.

 

Recommendations:

  • Carriers may be bred to normal animals (N/d x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • Breeding two carriers (N/d x N/d) is not recommended due to the possibility of 25% of the offspring being affected.
  • Affected animals (d/d) should not be used for breeding.

Testinformation: This test detects all four variants of the ACAN gene.

Eberth, J.E. : Chondrodysplasia-Like Dwarfism in the Miniature Horse. Theses and Dissertations–Veterinary Science. Paper 11. Entire thesis is available at http://uknowledge.uky.edu/gluck_etds/11:, 2013.

Metzger, J., Gast, A.C., Schrimpf, R., Rau, J., Eikelberg, D., Beineke, A., Hellige, M., Distl, O. : Whole-genome sequencing reveals a potential causal mutation for dwarfism in the Miniature Shetland pony. Mamm Genome 28:143-151, 2017. Pubmed reference: 27942904. DOI: 10.1007/s00335-016-9673-4.

Further information is available at Online Mendelian Inheritance in Animals.

SA Skeletal Atavism

Please be aware that by the conditions of the Skeletal Atavism (SA) patent license, the identity of the horse must be verified for CAG to perform the SA test. Samples may be collected by a veterinarian or studbook representative who can confirm the animal’s microchip identification. Alternatively, if the horse already has a DNA profile (on file with any laboratory or studbook), CAG can run a DNA profile from the submitted hair sample to confirm the animal’s identity


Abnormal bone growth in legs, resulting in dwarfism and leg deformities

General Information:

  • The term “atavism” originates from the latin word “atavus” (“ancestor”) and refers generally to the reoccurrence of ancient traits in recent species.
  • During the evolution of horses, the ulna and fibula fused, and modern horses have only one bone instead of two bones.
  • Skeletal atavism results in development of both fully sized bones again and causes severe deformation of bones and joints.
  • This disease leads to severe pain in the affected ponies and Miniature horses and hence to euthanasia due to poor quality of life.
  • Two mutations in the SHOX gene cause SA. Ponies may have both mutations and/or variants in the ACAN gene causative for the ACAN dwarfism.

Symptoms:

  • Malformation of legs and joints
  • Short, splayed legs
  • Progressive lameness
  • Impaired movement
  • Strong pain

Inheritance: autosomal-recessive

→ Only animals with two copies of the varaint (sa/sa) are affected. Animals with only one copy are clinically normal carriers (N/sa).

Possible Genotypes:

Genotype: The horse is:
Effects:
N/N normal. The horse has no copies of the genetic variant causative for SA and therefore cannot pass it on to its offspring.
N/sa a carrier. The horse is clinically healthy. The variant will be passed on to its offspring with a probability of 50%.
sa/sa affected. The variant will be passed on to all offspring. All offspring will be carriers (N/sa).

Recommendations:

  • Carriers may be bred to normal animals (N/sa x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • Breeding two carriers (N/sa x N/sa) is not recommended due to the possibility of 25% of the offspring being affected.
  • Affected animals (sa/sa) should not be used for breeding.

Test information: This test detects both deletions in the SHOX gene.

Rafati, N., Andersson, L.S., Mikko, S., Feng, C., Raudsepp, T., Pettersson, J., Janecka, J., Wattle, O., Ameur, A., Thyreen, G., Eberth, J., Huddleston, J., Malig, M., Bailey, E., Eichler, E.E., Dalin, G., Chowdary, B., Anderssson, L., Lindgren, G., Rubin, C.J.: Large Deletions at the SHOX Locus in the Pseudoautosomal Region Are Associated with Skeletal Atavism in Shetland Ponies. G3 (Bethesda) :, 2016. Pubmed reference: 27207956. DOI: 10.1534/g3.116.029645.

Tyson, R., Graham, J.P., Colahan, P.T., Berry, C.R.: Skeletal atavism in a miniature horse. Vet Radiol Ultrasound 45:315-7, 2004. Pubmed reference: 15373256.

Further information is available at Online Mendelian Inheritance in Animals.

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