Hydrocephalus in Friesian Horses
Hydrocephalus is a developmental disorder involving an accumulation of cerebrospinal fluid within the skull. This often results in foals born prematurely, stillbirth of affected foals and dystocia in dams. In Friesian horses, Hydrocephalus is inherited as an autosomal recessive mode. A nonsense mutation XM_001491545 c.1423C>T is associated with hydrocephalus in Friesian horses. Hydrocephalus is primarily a result of years of inbreeding in the Friesian horse population and the widespread use of some influential ancestors.
Foals can only be affected by Hydrocephalus if the foal inherits the disease from both parents. Parents that are carriers do not have any symptoms associated with the disorder. However, they will pass on a copy of the defective gene to their offspring 50% of the time. If breeding two carriers the foal has a 25% chance of being affected and a 50% chance of being a carrier
Testing for Hydrocephalus is valid for Friesian Horses.
Animal Genetics UK offers DNA testing for Hydrocephalus. The genetic test verifies the presence of the C>T mutation and presents results as one of the following:
|HC/HC||Affected||The horse carries two copies of the mutation and is homozygous for Hydrocephalus. The horse is affected.|
|n/HC||Carrier||Both the normal and mutant alleles were detected. Horse tested heterozygous for Hydrocephalus and is a carrier of the mutation associated with your breed.|
|n/n||Clear||Horse tested negative for Hydrocephalus and does not carry the gene mutation. The horse will not pass on the defective gene to its offspring.|
BMC Genomics. 2015 Oct 9;16(1):761. doi: 10.1186/s12864-015-1936-z. A nonsense mutation in B3GALNT2 is concordant with hydrocephalus in Friesian horses. Ducro BJ1, Schurink A2, Bastiaansen JW3, Boegheim IJ4, van Steenbeek FG5, Vos-Loohuis M6, Nijman IJ7, Monroe GR8, Hellinga I9, Dibbits BW10, Back W11,12, Leegwater PA13.