Overo Factor / Overo Lethal White Foal Syndrome (OLWFS)
Acronym: | OLWFS |
Gene: | EDNRB |
Mutation: | c.353_354delinsAG |
Inheritance: | Autosomal dominant (OVERO), autosomal recessive (OLWS) |
Sample type: | WBE (Whole Blood EDTA), HA (Hairs - with roots) |
Genetics and characteristics
Overo lethal white foal syndrome (OLWFS) is an inherited disease that affects several breeds of horses. Horses with OLWFS have an all-white coat and intestinal tract abnormalities that result in colic and related symptoms within 12 hours of birth. OLWFS is caused by a genetic mutation in the endothelin receptor type B (EDNRB) gene responsible for various signalling mechanisms that transmit information from outside the cell to the inside. The missense mutation in the EDNRB gene disrupts the production of melanocytes that produce pigment for coat colour and the formation of nerves in the intestinal tract, leading to intestinal obstruction and death a few days after birth.
OLWFS is inherited as an autosomal recessive trait, even though the Overo coat colour is dominant to normal solid colour. Meaning that the only horses to show this disease are homozygotes for the Overo allele carrying two copies of the mutation. OLWFS affects several horse breeds, including American Paint Horse, Miniature Horse, Quarter Horse, and Thoroughbred. The disease is incurable, but early detection by genetic testing can help identify carriers of the mutation and prevent further breeding with careful selection of mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
Healthywith normal coat color |
Horse does not have the gene with OLWFS associated mutation. Horse is healthy and has a normal coat pattern. |
Healthy - carrierwith Overo coat pattern |
Horse has one copy of the gene with OLWFS associated mutation. Horse is healthy and has Overo coat pattern. |
Affected |
Horse has two copies of the gene with OLWFS associated mutation. Horse is affected and likely to die shortly after birth. |
References:
Ayala-Valdovinos, M. A., Galindo-García, J., Sánchez-Chiprés, D., & Duifhuis-Rivera, T. (2016). New test for endothelin receptor type B (EDNRB) mutation genotyping in horses. Molecular and Cellular Probes, 30(3), 182–184. doi:10.1016/j.mcp.2016.03.005
Metallinos, D. L. , A. T. Bowling, D. L., & Rine, J. (1998). A missense mutation in the endothelin-B receptor gene is associated with Lethal White Foal Syndrome: an equine version of Hirschsprung Disease. Mammalian Genome, 9(6), 426–431. doi:10.1007/s003359900790