DBE Nadeya (DBE-NAD)

Overview

DBE-NAD is a large genetic change affecting the region that contains the PAX3 gene, first described by Abitbol et al. (2026). It was identified in the Ermine Trace Nadeya line of British Shorthair and British Longhair cats, founded in Russia in 2016.

Unlike DBE-CEL or DBE-ALT, which are small changes located within PAX3, DBE-NAD involves a much larger section of chromosome C1.

Location

DBE-NAD affects a large region of chromosome C1 that includes the entire PAX3 gene. Part of this region is deleted and another part is reversed. The important point is that a DBE-NAD cat has only one intact copy of PAX3 instead of the usual two. The affected region also contains several other genes, so although PAX3 is considered the most likely cause of the DBE phenotype, researchers cannot completely exclude an effect from the other genes involved.

Molecular Mechanism

Cats normally have two copies of PAX3, one inherited from each parent. In a DBE-NAD cat, one copy is missing because of the large genetic rearrangement. The remaining copy is enough for the cat to survive, but having only one working copy of PAX3 can affect pigmentation and eye colour.

This is known as haploinsufficiency — simply meaning that one working copy of the gene may not be enough to produce the usual effect during development.

This makes DBE-NAD different from variants such as DBE-RE, DBE-AGO and DBE-MARU, where the PAX3 gene is present but its protein-coding sequence is altered.

Associated Phenotype

Cats from the Nadeya line have been reported with:

● bilateral blue eyes

● odd eyes

● little or no white spotting

● latent (non-expressing) cats

The amount of visible expression varies between cats. In the 2026 study, all 39 DBE cats from the Nadeya line that could be phenotypically assessed carried DBE-NAD.

The founder, Nadeya, also carried the variant.

Hearing

Hearing information for DBE-NAD is still limited. The authors reported three deaf cats among tens of DBE kittens produced in the line. Based on the information available from the breeder, they did not find evidence suggesting that deafness was unusually common in DBE-NAD cats. However, the study did not include a large group of systematically BAER-tested DBE-NAD cats. For that reason, it is too early to say that DBE-NAD is not associated with hearing loss. More BAER data are needed.

Current Evidence

No genetically confirmed living DBE-NAD/DBE-NAD homozygous cat has been reported. DBE × DBE matings were performed in the Nadeya line, but the number of kittens born was lower than expected if all possible genotypes had survived. The breeding results were consistent with the possibility that kittens inheriting DBE-NAD from both parents may die during embryonic development. This is therefore different from simply saying that homozygous kittens have never been seen. The available breeding data specifically suggest that DBE-NAD homozygosity may be embryonically lethal. However, no affected embryo was genetically tested, so this remains an interpretation of the breeding data rather than a directly confirmed homozygous case.

References:

  1. Abitbol, M., Eiselé, T., & Lipovenko, E. (2026). Additional PAX3 Variants for Dominant Blue Eyes in Cats. Animal Genetics, 57(5), e70199. https://doi.org/10.1002/age.70199