Retinopathy with vitamin E deficiency / RVED (TTPA-related) - Dog

What does this test examine?

This genetic test examines the TTPA deletion c.23_124del in dogs. This variant causes retinopathy with vitamin E deficiency, commonly abbreviated as RVED. The condition is also described as ataxia with isolated vitamin E deficiency, AVED, central progressive retinal atrophy, vitamin E deficiency retinopathy and retinal pigment epithelial dystrophy.

What does RVED mean?

The TTPA gene encodes alpha-tocopherol transfer protein, which is important for vitamin E transport in the body and to the retina. Dogs with two copies of the tested deletion can develop an inherited vitamin E transport disorder. The main effect is retinal damage with night blindness, pigmentary changes, progressive loss of vision and eventually blindness. Some dogs can also show neurological signs such as ataxia or reduced proprioception.

Practical value of this test

RVED is inherited in an autosomal recessive manner. Carriers usually look healthy, so the variant can remain hidden in a breeding line without DNA testing. The result gives breeders and owners clear information to avoid risk matings and to place dogs with eye signs or family history more accurately within the pedigree.

• Distinguishes clear dogs, carriers and genetically affected dogs.
• Supports breeding plans in English Cocker Spaniels, Field Spaniels and Polish Lowland Sheepdogs.
• Allows carriers to be managed responsibly without producing affected puppies.
• Adds clarity when night blindness, retinal changes or progressive vision loss occur in a line.

Result and inheritance

A dog with N/N does not carry the tested deletion. A dog with N/del is a carrier and can pass the variant on. A dog with del/del has the genotype that causes inherited RVED.