DBE Marusya (DBE-MARU)

Overview

DBE-MARU is a coding variant of the PAX3 gene, first described by Abitbol et al. (2026). It was identified in the Cyrridwen Marusya line, which began in Russia in 2019 with an outbred Domestic Shorthair female named Marusya. Exotic Shorthair, Persian and British cats were later used in the development of the line. DBE-MARU changes the part of PAX3 that contains the instructions for making the PAX3 protein.

Location

DBE-MARU is located in exon 5 of the PAX3 gene on chromosome C1. Exons are the parts of a gene that remain in the final genetic message used to make a protein. The DBE-MARU mutation creates an early stop signal within PAX3. This means the cell is instructed to stop making the PAX3 protein before the protein is complete.

Molecular Mechanism

DBE-MARU is a coding variant predicted to produce a shortened PAX3 protein. The mutation creates a premature stop signal at amino acid 262. As a result, the predicted protein is missing approximately 46% of its normal length. This distinguishes DBE-MARU from DBE-CEL and DBE-ALT. CEL and ALT are located in non-coding parts of the gene and are thought to affect how PAX3 is regulated.

DBE-MARU directly changes the instructions used to make the PAX3 protein.

Associated Phenotype

Cats from the Marusya line have been reported with:

● bilateral blue eyes

● odd eyes

● little or no white spotting

● latent (non-expressing) cats

Expression therefore appears to be variable, as it is with several other DBE variants. In the family studied, all 14 DBE cats born from DBE × non-DBE matings carried one copy of DBE-MARU. Marusya herself also carried the variant.

Hearing

There are currently no published hearing data for DBE-MARU. The 2026 study did not include BAER results for cats from the Marusya line. This means we currently do not know whether DBE-MARU increases the risk of unilateral or bilateral deafness. The absence of reported deafness should therefore not be interpreted as evidence that hearing is unaffected. BAER testing will be important as more DBE-MARU cats are studied.

Current Evidence

One particularly important case was reported from a DBE × DBE mating. An abnormal kitten was born and died at birth. Genetic testing showed that this kitten had inherited DBE-MARU from both parents and was therefore DBE-MARU/DBE-MARU homozygous. This makes it different from DBE-NAD, where homozygous lethality is suggested by breeding results but no homozygous kitten or embryo has been genetically confirmed. For DBE-MARU, the homozygous genotype itself was confirmed. However, this was only one kitten. It therefore shows that a homozygous DBE-MARU kitten can occur and can have a severe outcome, but one case alone cannot tell us the full range of effects caused by DBE-MARU homozygosity.

No genetically confirmed living DBE-MARU homozygous cat has been described in the scientific literature to date.

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