Achromatopsia 2 / day blindness (CNGA3-related) - German Shepherd

Achromatopsia 2 in the German Shepherd

This genetic test assesses the CNGA3 c.1270C>T variant that causes achromatopsia 2 in the German Shepherd. The condition is also known as day blindness, cone degeneration, cone degeneration disease, CD, ACHM and hemeralopia.

CNGA3 is important for signal transduction in the cone cells of the retina. Cones support sharp daylight vision, colour vision and adaptation to bright light. When both copies of the tested variant are present, this system does not function properly and clear day blindness develops.

This German Shepherd variant is a missense variant that disrupts CNGA3 protein function.

What can the owner or breeder notice?

• Affected puppies usually show day blindness from about 8 to 12 weeks of age.
• Bright light can be uncomfortable or painful, so puppies may seek shade or darker areas.
• Vision in dim light remains much better than vision in daylight.
• Colour vision and sharp daytime vision are reduced because the cone cells are affected.

Practical value of this test

• The result clarifies whether the dog is clear, carrier or genetically affected for this CNGA3 variant.
• The trait is autosomal recessive: carriers are usually healthy but can pass the variant to offspring.
• By identifying carriers deliberately, breeders can avoid combinations that produce puppies with two copies and achromatopsia.