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These articles describe blue-eyed cats in colours other than white, bicolour or colourpoint (Siamese pattern). Some of the Russian breeds have variable spelling when the breedname or cat name is translated into the Roman alphabet. This information will be updated as more of the gene's effects become apparent. There are currently no DNA tests for the genes involved.
There is no single "DBE" mutation so it is important to know which gene you are discussing/working with as they should not be crossed to each other. There is "Altai DBE," "Barnaul DBE," "Australian DBE," DBE's identified by the region discovered or the foundation cat's name or "unknown DBE" etc. The modern blue-eye breeds are not Ojos Azules - that breed never made it out of America and the more recent mutations do not have the same side-effects.
Blue-eyed non-white cats were discovered almost 20 years apart and on almost diametrically opposite regionss of the globe: the California Ojos Azules and the Kazakhstan Altay Blue-Eyes. In both cases, outcrossing showed that the blue-eyed genes were dominant type over the ordinary yellow, copper or green colours. In both cases there is at least a tiny white marking, most often at the tail-tip, but it might also be a white locket, white back paws or a white smudge on the face. Due to incomplete penetrance of the gene, the size of the white marking ranges from just a few hairs to a large white patch (in homozygotes).
It is currently assumed - though DNA analysis is still ongoing - that the Altai blue-eyes gene is an allele of the white spotting gene and that it is "weakest" in comparison to the usual white spotting gene which causes the familiar bicolour range and it may also interact with the white spotting gene. Genes encode for proteins and any change to a protein can have other effects. In 2023 Marie Abitbol isolated mutations on one chromosome for 2 of the DBE lines (Roxi's and Seymour's); these mutations are not in exactly the same area. For a 3rd line of DBE cats, the gene is completely different. This is why the different mutations should not be bred together.
The first modern attempt to create a blue-eyed breed whose eye colour did not depend on having a white face was in the USA in 1984. This was the Ojos Azules which is unrelated to the modern DBE breeds.
In 1997, Lyubov Borisovna Zikeeva from Ust-Kamenogorsk (Kazakhstan) noticed blue-eyed cats on the street and decided to re-establish a truly blue-eyed breed.
The DBE gene in the Heavenly Eyes breeding programme comes from Seymour. He was bred to a British Blue Shorthair and produced Nikita'l Daisy (bred by Iryna Merzlenko, developer of the Topaz breed).
Elizaveta Lipovenko has a spontaneous mutation in her British Shorthairs, producing blue-eyed and odd-eyed chinchilla/silver shaded and tipped golden cats.
In August 2016, the LOOF (French registry) Committee of Standards approved the introduction of the blue eye colour in the British Shorthair/Longhair. In 2023 the Celestial was recognised as a breed.
In 2019, Nataliia Zalesskaia (Cyrridwen cattery) in Volgograd, Russia, found a blue-eyed domestic shorthhair named Marusya and started working with this mutation.
Patrice Tremblay introduced (Chatterie de l'Olynx, Québec, Canada) the DBE gene in Highlanders from Nikital Jaguar of Olynx under the Chats Canada Cats.
A blue-eyed strain initially believed to be from Rociri Elvis in the Netherlands, but DNA traces it to a latent gene derived from Justcoons Ha Shisch, and the latent gene again jumped generations and was traced to JW Olmocabe's Alastor, but can’t be traced any further back.
Blue eyes have been introduced into the Munchkin breed (self colours only) in Australia by David Karamatic. He imported Celestial British "Maidee" (Altai Gene).
Cats with vivid blue eyes were discovered in New Mexico among feral cat populations in the 1980s. In 1984, a blue-eyed tortoiseshell named "Cornflower" was bred to non-blue-eyed males resulting in litters of blue-eyed kittens. This showed the trait to be dominant. The breed was named "Ojos Azules," this being Spanish for 'Blue Eyes'.
In 2017, Josee Rodrigue of Gatineau, Quebec, Canada, imported Alaska's Ninja of RagaMania, an odd eyed male from Chloe Alaska (who had Nikita'l Gioia bred by Iryna Merzlenko), to introduce the Altai blue eyed gene into theRagaMuffin.
In 2020, Helen Fitton reported odd-eyed Ragdolls whose eyes were distinctly different shades, with one being blue because of the colourpoint gene, but the other being blue due to a spontaneous mutation (possibly in the white spotting gene) for Dominant Blue Eyes (DBE).
Elena Nekrasova (Slavicat cattery) acquired a blue-eyed tortoiseshell, Malvina, that became the ancestor of a line of DBE Siberian cats with a dominant gene for blue eyes
Dominant blue eyed mutations have been discovered in Queensland, Australia and Chengge, China. Blue eyed Burmillas, Burmese and Tonkinese have occurred.
Blue-eyed cats occur in the random population all around the world and many are neutered as pets. Until the development of the Ojos Azules, and then the Russian mutations, most were seen as curiosities and not bred. Those found by rescue organisations are neutered as a matter of course.
The Altai gene and the Seymour gene are the best studied at present. They have been bred and studied over multiple generations and breeders have tested their cats' hearing as well as observing any physical abnormalities. Most physical anomalies are cosmetic, but some have reported deformed or absent tear ducts. Whether this is associated with one gene or with mixed genes isn't yet known. Where it did occur, it was strongly linked to the blue eye as odd-eyed DBE cats were only affected on the blue side. More than 50 heterozygous French Celestial Shorthairs (Altai gene) had their hearing tested and none were found to be deaf. Only the homozygous Celestials showed bilateral deafness so blue-eye to blue-eye matings were prohibited in this breed.
In contrast, a German breeder of DBE Maine Coons (undisclosed mutation) has found that her DBE Maine Coons with full colour can be deaf and this is not uncommon. Other breeders have had deaf full-colour Maine Coons from the same line. The DBE Maine Coon from this line has the wider-spaced eyes or telecanthus when compared to one with normal eye colour. when I look at the photos of the two cats in blue, I have to say that the blue-eyed one looks different. The eye spacing is characteristic of the mutation which means it is unlikely to improve with each generation of breeding. Although the mutation used was not disclosed, this deafness in full-colour DBE cats has been seen in the Aktau blue-eyed mutation (tracing to a cat called Caspian Black Hole). Some Aktau lines were bred to Barnaul mutation lines (founded by Velvet Slavicat). There is also the Rociri Elvis mutation which seems to be a mutation (in the Netherlands) of the "normal" white spotting gene. Some breeders have used the Rociri Elvis gene (a "latent" DBE gene that originated in his mother's line) as the basis and sometimes mixing with Altai or another mutation to improve eye colour!
THE WFA "DBE PROGRAMME" (RUSSIA)
The Russian WFA expanded the number of breeds which are permitted to include the DBE trait. Initially their DBE breeding programme was restricted to British Shorthairs/Longhairs. It now includes Scottish Folds (non-folded Scottish Shorthairs/Longhairs are interbred with British Shorthairs/Longhairs) and Maine Coons (both original and polydactyl). It is evident from pedigrees that DBE cats have been introduced into the programme and allowed to interbreed even if they have different ancestors and different genes or unknown origins. The early issues with the Topaz breed prove this mixing of DBE genes to be risky. There appears to be little control over which DBE genes are being introduced, many appear to come from outcrosses to local domestic shorthairs with unknown mutations.
To prevent issues caused by DBE gene interactions the DBE version of an existing breed should be developed as a separate breed. Only one source of DBE gene should be used in the breed. Registries should prohibit mixing different DBE genes in a single breed. In Europe the most widespread DBE genes are the Altai and Seymour genes. Some registries require DBE versions of breeds to be given new breed names to keep their gene pool separate from their non-blue-eyed ancestor breed.
Many of the DBE versions of existing breeds are TICA-registered, but with no details of which DBE gene they have. The DBE ancestor might be a domestic cat with unknown origins. For the wellbeing of the breed in later generations, breeders need to declare which gene they are using to avoid mixing different genes into a single breeding line. The DBE version of an existing breed should have a separate name to avoid the gene entering the wider gene pool via a "latent" (a genetically DBE cat that does not have the blue eyes).
Under the Russian DBE programme, the DBE trait is being introduced into numerous breeds. There are multiple DBE versions of British Shorthair/Longhair cats in Russia and neighbouring countries and it is almost inevitable that these will be interbred later on with unknown consequences. In Canada, Blue-Eyed Maine Coons have both the Rociri Elvis gene and the Altai gene. Breeders plan to combine these genes and may see a repeat of the Topaz situation when 2 DBE genes were combined (poor immune systems, kitten deaths). There are also multiple lines of Munchkin with different DBE ancestors. At present they are widely separated - one in Russia (Karagaisky gene) and the other (Altai gene) in Australia - and unlikely to be bred together.
Since the discovery of the Altai gene, Dominant Blue Eyes has become "the next big thing" (previously the Munchkin gene had been the "big thing" in cats). Anyone who acquires any unneutered blue-eyed cat that isn't the result of the normal white spotting gene can create a DBE version of a breed. The Russian DBE programme has exploded and many of the breeds have untraceable DBE mutations.
DBE has appeared in the following additional breeds in Russia and neighbouring countries under the "DBE programme" umbrella: American Curl, Bambino, Cornish Rex, Devon Rex, Lykoi, Selkirk Rex, Siberian, Sphynx and DBE cats are advertised on Russian Facebook pages/groups as being available to mate to Singapura and Bombay breeds. None of these specify which gene is used. Altai DBE Lykoi are bred in the USA derived from Topaz cats.
DBE is also becoming popular in China, mostly using genes from Ukrainian cats.
CONSIDERATIONS FOR ALL BLUE-EYED BREEDS
There are various known and unknown genes involved in white spotting and in blue-eyes. In solid white and high white cats there is a link to deafness because melanin is involved in the development of the inner ear (the part that detects sound vibrations). BAER testing (acoustically evoked brain stem responses) is used by many European breeders to ensure that they don't deliberately breed deaf cats. The prevalence of deafness and partial hearing in an experimental colony of white cats was 67% (deaf - 0.55 coefficient of heritability) and 29% (partial hearing - 0.75 coefficient of heritability) which suggests a pleiotropic major gene (a gene that has 2 seemingly unrelated traits) and the likelihood of polygenes.
Geigy CA, Heid S, Steffen F, Danielson K, Jaggy A, Gaillard C (2007). "Does a pleiotropic gene explain deafness and blue irises in white cats?". Veterinary Journal. 173 (3): 548 553. PMID 16956778.
This was commented upon by Strain GM, in "Deafness in blue-eyed white cats: the uphill road to solving polygenic disorders."Vet J. 2007 May;173(3):471-2. Epub 2007 Feb 21.
Until you are able to test outcross cat(s) and they have the same DBE mutation as your current DBE lines, do not breed them together. Instead of improving eye colour you risk potentially serious problems in the descendants and risk ruining your breeding programme.
WHEN GENES INTERACT
The DBE mutations could be different mutations of the same region of a single gene, or mutations in different regions of a single gene, or mutations of different genes entirely. Genes come in paired alleles; each allele could have the same mutation or a different mutation (or no mutation at all). A cat might be heterozygous for 2 mutations at a single region AND heterozygous for mutations at a different region. It could be homozygous at both regions, or heterozygous at one region and homozygous at another region. A worst case scenario is that the gene is so badly damaged by the mutations that it cannot function, and no processes downstream of that gene can function properly (or at all) – resulting in deformity, disability or non-viable embryos. And that’s just for one gene! A cat might ALSO have a DBE mutation on a completely different gene, and the two different genes might also interact. Even if the genes are on a different chromosome, they might be involved in the same development pathway and again, their interaction could be disastrous.
This is why breeders should not mix multiple DBE mutations (mutations from different origins) into one breed. Breeders should avoid breeding different DBE breeds together unless both come from the same original cat and have the same mutation. A single "DBE Programme" that does not separate the genes is likely to end in disaster further down the line.
The "blue eyes is the next big thing" effect has become so widespread that a number of catteries now state they "do not work with the blue-eye genes" and that their blue-eyed cats are due to the colourpoint gene or the white gene.
