Test Detail

PRA-NECAP1 (Giant Schnauzer)

Ocular · Dog

Form of progressive retinal atrophy (PRA) of the Giant Schnauzer associated with a variant in the NECAP1 gene, which encodes a protein involved in endosomal trafficking of photoreceptors. It causes progressive photoreceptor degeneration with initial night blindness and progression to complete blindness. It is one of the breed-specific genetic variants of PRA.

Inheritance pattern	Autosomal recessive
Gene / Mutation	NECAP1 c.544G>A p.(Gly182Arg) (g.37468611G>A; OMIA002198-9615; missense variant, NOT frameshift). It was identified in a Giant Schnauzer with PRA of onset around four years of age. Do not confuse with human NECAP1 variants causing epileptic encephalopathy, which are a different phenotype.
Penetrance	In the homozygous animals described, PRA manifests (apparently high penetrance in the published cases), but the number of dogs characterised is small. Heterozygotes are asymptomatic carriers. Complete penetrance in homozygotes should not be stated categorically with the current evidence.
Code	swhi
Turnaround time	15 days
Price	52,60 €

Incidence

Giant Schnauzer is the characterised breed. The carrier frequency in the breeding population is not reliably published (limited data).

Breeder management

- Genotype breeding animals before mating
- Do not mate two carriers: 25 % risk of affected homozygotes
- A carrier may be mated to a clear animal; offspring intended for breeding must be tested
- Exclude affected homozygous animals from breeding
- After a confirmed case, do not repeat the parental mating and communicate the status to the buyer

Specialist notes

Differential diagnosis with other canine PRAs (PRA-PRCD, PRA-CRD1/2, PRA rcd1-rcd4) and with senile cataracts. The fundus and electroretinography guide; the NECAP1 molecular test confirms. Remember the molecular heterogeneity of canine PRAs: use a broad panel if the suspicion is not confirmed with the NECAP1 variant.

References

1. Hitti RJ et al. 2019. Whole Genome Sequencing of Giant Schnauzer Dogs with Progressive Retinal Atrophy Establishes NECAP1 as a Novel Candidate Gene for Retinal Degeneration. Genes (Basel). PMID: 31117272
2. Kang M et al. 2025. PCR-based detection of hereditary mutations in SLC2A9, BTBD17, and NECAP1 among native Korean dog breeds. J Vet Sci. PMID: 40765230
OMIA002198-9615.

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