This case study is published in full, and kept current, in the Blue Eyes Directory as case study three. Read it in the Blue Eyes Directory.

Three: how a variant arrives in a breed

A breed can acquire the same trait more than once, by routes that do not meet. Where that happens, a rule written for the breed governs cats whose genetics differ. The Siberian is the clearest documented instance in this survey, because both the genotyping and the genealogy exist and they do not say the same thing.

What the research found in the breed

DBE^CEL (Roxi) is confirmed by genotype in the Siberian. Abitbol, Couronné A, Dufaure de Citres C and Gache V, Animal Genetics 2024;55:670-675, Table 1, records four Siberians heterozygous for the variant. In the same year Abitbol M, Dufaure de Citres C, Rudd Garcés G, Lühken G, Lyons LA and Gache V, Animals 2024;14:1845, Table 2, genotyped four Siberians with the trait and found them wild type for DBE^ALT. Wild type means the ordinary, unmutated version of a stretch of DNA, so a cat genotyped wild type for a variant does not carry that variant. No Siberian has been reported positive for DBE^ALT in any published series.

One mating carried two variants into the breed

Breeder-compiled genealogy C7, headed Blue-Eyed Siberians (Altai Gene), records a single point of entry. Kaena, out of March (Marta) by Seymour (Seimur) and so of the DBE^ALT lineage, was mated to Lazuli, born 2 April 2015, a son of Roxi and so of the DBE^CEL (Roxi) lineage. The mating took place on 18 July 2016 at the D'Aerlin cattery in France and produced seven kittens. Merlin comes out of that litter, and every Siberian below him on the chart descends from a cat with one carrier parent of each variant.

The link into the current population

The branch does not stay outside the breed. The litter of 14 November 2021 is by a Maine Coon sire, Kiwano's Rock-a-Hula, MCO n 09 22, born 29 September 2012. The litter of September 2023 is by a Siberian sire, Molaska Nouky, SIB ns 24, born 13 July 2017, out of Sabrina Legende des Alpes. Two of the five kittens of that litter are blue-eyed, Uill and Uindy. The descendants of the 2016 mating are therefore being bred to registered Siberians, and the trait is passing into the current population by that route.

Every cat below Merlin is registered XLH, experimental longhair, while the sire brought in for the 2023 litter is registered SIB. The register therefore records the branch as experimental at the same time as it records a Siberian stud in it. Which of the two variants these cats carry has never been established. Merlin is out of a carrier of each and has not been genotyped, and the chart assigns DBE^ALT throughout on no test. DBE^CEL (Roxi) is recorded in some cases below him on messybeast.com and remains officially unpublished.

The other blue eyes in the breed, and why they are not this trait

Breeder-compiled genealogy C3, headed DBE Siberians, unconfirmed if Altai gene or Barnaul gene from Altai Region, records a Russian population with a pedigree running back to Figaro Onix Gloria, SIB n 22, born 1 October 2006. It has been read as a second and older source of the trait in the breed. Its two earliest cats recorded as blue-eyed are white cats, and their certified pedigrees account for the blue eye without reference to PAX3.

Its oldest generations are ordinary registered Siberians. Figaro Onix Gloria and Blue Topaz Grilyazh, the chart's earliest dated cats, both appear as fourth-generation ancestors of registered Swiss Siberians of the Légende des Alpes cattery. Nine pedigrees of that line have been read: Ornella and O sole mio, littermates born 1 September 2018; Robin, 8 May 2020; Sherkan, 15 January 2021; Thaïs, 13 February 2022; U R Sunny Leo and Umbria, littermates of 17 September 2023; Umbriel, 6 September 2023, the dam of Abriel; and Abriel, 20 February 2025. Each is complete to four generations and the first eight are 0.0 per cent inbred with thirty unique ancestors of thirty possible. In those pedigrees they are SIB n 22 and SIB n 09 24, and no eye code is shown on any ancestor in any of the nine. That absence carries no weight on its own: the pedigree database does not record an eye colour on every entry, so where no code is shown nothing is recorded either way, and no cat is thereby established as not blue. What the nine pedigrees do establish is a matter of record rather than of recording: neither the chart's blue-eyed cats nor any cat of the Merlin branch appears in any of them. The early generations of C3 stand in these pedigrees as ordinary breed stock, drawn into the chart as ancestry.

• V*Grand Sineglaziy Angel, SIB w 61, born 20 April 2010. Four generations, twenty-eight ancestors of thirty possible, inbreeding 3.52 per cent. His sire, V*Rafaele Sineglaziy Angel, is NEM n 21, and the sire line is Neva Masquerade throughout, so he carries colourpoint. His dam, Lu-lu Beliy Sibirjak of Sineglaziy Angel, is SIB w 64, white with green eyes, out of CH Belosnezhka Sarji SIB w 64, out of IC Jhuliana Belosneghka SIB w 61, born 5 May 1999 to two foundation cats.
• Zephir Taiga Star, SIB w 61, his son. Four complete generations, thirty ancestors of thirty possible, inbreeding 8.01 per cent. White from his sire, and a Neva Masquerade dam, NEM n 21.

Neither pedigree holds a cat of any DBE line. Both were read from PawPeds, and both are complete enough to show it: the white and the blue eye descend the dam's line from foundation stock, skipping two generations of white green-eyed cats on the way, which is what dominant white does, and the other side of each pedigree is colourpoint.

The registrations are exactly what the breed's own standard provides for. FIFe permits a blue eye in the Siberian with EMS codes w, 01 and 02, and requires one in the Neva Masquerade, so a white Siberian coded 61 is a registration the standard anticipates rather than a finding. Both cats are recorded in this survey's register as blue eyes attributed to another cause.

Every remaining dated blue or odd-eyed cat on that chart is 2018 or later, after the mating of July 2016. A further group, the Malvina line, begins with a Siberian taken off the street in Barnaul in 2015 and has no variant established for it either. The survey therefore records one documented route by which a PAX3 variant reaches the Siberian, and it is the route through Merlin.

Every route to a blue eye recorded in the Siberian

A blue eye in a cat has more than one cause, and the Siberian holds most of them at once. Three of the causes are ordinary and have nothing to do with PAX3: the colourpoint gene, which every Neva Masquerade carries; dominant white, which makes a white cat; and white spotting, which makes a cat with white patches. Three more are routes by which a PAX3 variant, or a suspected one, has entered the breed. The table separates them, because a rule written for the breed reaches all six and a test settles only some.

The last row is why none of this can be settled by eye. Every cat on the Merlin branch and on the Barnaul route is a tabby or a tortie with white. None is pointed and none is white, so the colourpoint and dominant white rows do not explain them. What is left is white spotting or a PAX3 variant, and the Schneesternchen cats are five Siberians of that exact description that were tested and turned out to be neither DBE^CEL (Roxi), nor DBE^ALT, nor DBE^RE.

So the position for the breed can be stated exactly. DBE^CEL (Roxi) is in the Siberian and was confirmed by genotype. No Siberian has ever returned a positive test for DBE^ALT, and four were wild type for it, meaning they carried none of it. Everything else, the Merlin branch, the Barnaul route and the Great Joy litters, is a blue eye with a documented pedigree and no genotype. That is one question, and a panel test on a handful of named living cats would answer it.

The rule the breed is governed by

FIFe's Siberian rule, FI and SK Proposal 1, in force 1 January 2026, allows blue eyes in the Siberian only with EMS codes w, 01 and 02, and requires any other blue-eyed or odd-eyed Siberian to be registered as XLH * 61 (SIB) or XLH * 63 (SIB), with no re-registration and no breeding. Its motivation states that in Siberians blue eyes are “likely caused by a variation of the so-called Altai gene (DBE^ALT)”. That is the one variant for which no Siberian has ever returned a positive test, and the four Siberians genotyped for it were wild type, meaning they carried none of it.

The same shape in a second breed group: the Munchkin and the Minuet

The Siberian is not the only breed group this survey can show being reached more than once. The Munchkin group is reached twice, by routes that do not meet, and the two rest on different kinds of document: one on registration certificates, the other on a breeder's account of where cats were sold.

The two routes have nothing in common. One begins with a village cat in the southern Urals a decade before any variant was described and reaches a breed through household-pet registration. The other begins with Roxi and reaches a related breed through a documented sale. Only the second carries a variant, and it carries it because the line it came from was genotyped.

The Céleste route into the Minuet is documented twice, by two separate sales. The founding cattery's dispersal record has Muscari of Aerlin into the Minuet at the Leonprime cattery, and Mistral and Neytiri into the Minuet and the Scottish Fold at the Miss Kitty cattery in Canada. The Minuet is the Munchkin crossed to the Persian, so DBE^CEL (Roxi) is in the Munchkin group twice over, by sale, from a line that has been genotyped.

The Iberis Munchkins are not on that route. Certificates P3 and P4 and PawPeds pedigree P20 run them back to Semyon and to Russian household-pet foundation cats, and nothing in any of those documents touches the Céleste, Roxi, Lazuli or Nikita'l Seymour. Their blue eyes have no identified cause, and no Munchkin has ever been genotyped for this trait.

So the Munchkin group holds at least two separate sources of a blue eye, and the genealogies are what establish it. One is a named PAX3 variant with a commercial test behind it. The other is unidentified, and whether it is PAX3 at all is unknown. A DBE^CEL test clears a cat of the first and says nothing whatever about the second, which is the exact position a breeder in that group is in, and the exact position a rule written on eye colour cannot distinguish.

The founding cattery's own record of where the cats went

The routes above are traced from pedigrees. There is a second kind of evidence for the same question, and it comes from the breeders rather than from the registries: the founding cattery published its own account of which cats it sold, to which catteries, in which countries and into which breeds. It is reproduced here because it is the only document in this survey that shows a variant leaving one breed for six others as a deliberate act, with the receiving catteries named.

Two things follow from reading it as a whole. The variant reaches six breeds in about two years, and every step is a sale between named catteries, not a coincidence of separate populations. And the chart labels a variant on five of the six rows and a query on the sixth, which is the same pattern the genealogies show: attribution travels with the cats, faster and further than any test does.

The same shape in the Maine Coon, and the one route that has a genotype behind it

The Maine Coon is the third worked example in this case study and it is the strongest of the three, because it is the only one where the genotyping settles which of two variants passed. The founders and the dates come from case study two, which follows the same two cats into the British Shorthair; what is set out here is how the variant arrived in this breed.

This survey establishes the sequence, and it does so from dated records rather than from anybody's account of them. The animals below are named, coded and dated; the LOOF dates are the registry's own; the variant descriptions are the peer-reviewed literature. The steps were assembled by transcribing the genealogies into this survey's register and reading them against those records, so every row can be checked against a document rather than against a recollection. The dates settle the direction of transmission on their own, whatever anybody believes about it.

One statement in this section is the compiler's rather than the record's, and it is marked where it appears: the heading on the genealogy, “blue-eye line created using Roxi and Seymour genes”, which is how that compiler describes the programme. It is not relied on for any step in the table.

Blue-eyed Maine Coons carrying this variant were being bred four to five years before the breed the variant is named after existed as a breed at all. A Maine Coon of this line cannot have taken DBE^CEL (Roxi) from the Céleste. Both took it from Roxi, by separate routes, and the naming records the later of the two.

The two branches leave Roxi by two different offspring. The British Céleste descends from Roxi through his son Lazuli, a Topaz. The Maine Coon line descends from Roxi through his daughter Nikita'l Pheer-Ca, dam of Nikita'l Markiss. Both branches reach a recognised breed by an outcross, and both are dated in the register. Nikita'l Markiss, born 26 March 2016 and registered an experimental longhair, was mated to the Maine Coon Celebrity, born 20 November 2016 and not blue-eyed, and their son Blue Ridge Ynjir, born 8 January 2018, is the first Maine Coon of the line. The step is established from the genealogy transcribed into this survey's register, where each of the four animals carries its own entry, its date and its parents. Neither route passes through the other. Neither breed took DBE^CEL (Roxi) from the other. They are sibling branches from one founder, which is what the published account describes when it records the Céleste as “created in France using an outbred male born to the Roxi sire” and the Maine Coon lineage as “founded by a Topaz cat”.

And one consequence of the table has to be stated, because it bears on every Maine Coon of this line. Nikita'l Markiss is not simply downstream of both founders. He is the son of a Seymour-line sire and a Roxi-line dam, so he may carry one copy of each variant, and every Maine Coon on the genealogy descends from him through Celebrity. Cats of that line may therefore carry DBE^CEL (Roxi), or DBE^ALT, or one of each, and a cat with one of each is a compound heterozygote, which is the combination this survey records as producing deaf and dead kittens. That is why the Maine Coon row against DBE^ALT in the breed table is a testing priority rather than a settled attribution: no genotype for DBE^ALT in a Maine Coon has been published, and the question can be answered for any individual animal by a panel test.

Source: Blue Eyed Maine Coons genealogy, breeder-compiled, read 13 August 2026. Graded reported: no cat on it carries a genotype, and the genealogy marks the eye phenotype only. The LOOF dates are from the registry's own record. The published route, “the Maine Coon lineage founded by a Topaz cat”, is Abitbol et al., Animals 2024, 14(13):1845, which names no individual animals.

What this establishes about how a variant arrives in a breed

• A breed can hold the trait by more than one route, and the routes need not carry the same variant. One route into the Siberian is dated and traceable to a single mating on 18 July 2016 that held both DBE^CEL (Roxi) and DBE^ALT. A second is a Russian population documented from 2006 with no variant established. A rule written for the breed reaches all of them.
• A chart's title is not evidence of a variant. C7 is headed Altai Gene and assigns DBE^ALT to nineteen cats on the strength of that heading. The chart also enters Roxi, Nikita'l Seymour, Kaena and Lazuli as Siberians, which none of them is on any other record. A genealogy compiled before a variant was named carries the naming of its own date.
• An experimental register is not a barrier. The branch is registered XLH throughout and has taken a Maine Coon sire in 2021 and a Siberian sire in 2023. The register records the cats as experimental while the matings move the variant into two recognised breeds.
• Attribution belongs to the individual animal and is established by genotype. Twenty-six cats of this branch are recorded and none is genotyped, so this survey attributes no variant to any of them. What the pedigree does establish is narrower and firmer: Merlin is out of a carrier of each variant and is blue-eyed, so he carries one of them or both, and every cat below him may carry either, both or neither. A cat with one copy of each is a compound heterozygote, the state this survey records as producing deaf and dead kittens. The cats that would settle it are alive, registered and identifiable by name.

Sources: breeder-compiled genealogies C3 and C7, close-up tiles supplied to this survey on 13 August 2026; Abitbol, Couronné A, Dufaure de Citres C, Gache V, Animal Genetics 2024;55:670-675, Table 1; Abitbol M, Dufaure de Citres C, Rudd Garcés G, Lühken G, Lyons LA, Gache V, Animals 2024;14:1845, Table 2; FIFe General Assembly, FI and SK Proposal 1, sections 6.22 and 6.23, in force 1 January 2026.