Congenital stationary night blindness 2 / CSNB2 (GRM6-related) - Horse

What does this test analyse?

This genetic test analyses the GRM6 c.533C>T variant in horses. The condition is described as Congenital Stationary Night Blindness 2, CSNB2, congenital stationary night blindness and non-progressive night blindness.

What does it mean for the horse?

GRM6 is involved in retinal signal transmission. Horses with two copies of the tested variant can see poorly or abnormally in low light, while daytime vision may be less obviously affected. This matters for safety, training, stable management and breeding decisions.

The test clarifies whether a horse is clear, carrier or has two copies of the CSNB2 variant. In breeds and lines where night blindness occurs, this information helps breeders plan matings and avoid unexpected risk combinations.

Practical value of this test

• Detects the known GRM6 c.533C>T variant.
• Helps identify carriers before two carriers are mated.
• Gives breeders clarity about the risk of foals with night blindness.
• Supports interpretation of uncertain behaviour or vision problems in low light.

Inheritance and result

CSNB2 is inherited as autosomal recessive. Carriers with one copy are usually not night blind due to this variant, but can pass it on. Horses with two copies develop the genetic CSNB2 condition.