KITLG and Coat Intensity: The Gene Behind Deep Red, Black, and Silver Poodles

Two poodles, same litter. One is a blazing, saturated mahogany red; her brother is a decent but unremarkable apricot. Two more, different litter: one black puppy stays a deep, ink-black adult, and his sister is a "black" that always reads a shade lighter, almost pewter, even though nobody in the pedigree is silver or blue. Breeders have always talked about these dogs as if depth of colour were its own trait, separate from which colour a dog is. A 2020 study out of UC Davis found a real piece of why: a single DNA variant near a gene called KITLG that tracks with pigment depth on both sides of the coat, phaeomelanin (red) and eumelanin (black) alike (Weich et al., 2020).

This article covers what that study actually found in poodles specifically, what it did not control for, and why — despite a striking result — it does not change anything about how this site tests, or does not test, for red intensity, dilution, or greying.

What KITLG Is, and What Kind of Variant This Is

KITLG (Kit ligand) is a gene with a long, well-established role in pigment cell biology across mammals. The variant the UC Davis team found is not a single-letter change (a SNP) of the kind that defines most loci on this site. It is a copy-number variant (CNV): a roughly 6,000-base-pair stretch of DNA, sitting about 152,000 bases upstream of the KITLG gene itself, that some dogs carry in more repeated copies than others. Think of it less as a switch and more as a dial — the more copies a dog carries, the more intensely its pigment tends to be expressed.

The Poodle Numbers

The researchers measured exact copy number with digital droplet PCR across dogs sorted by owner-reported colour. In poodles, the pattern held on both sides of the coat:

Both comparisons were highly significant (red vs. cream: p = 4.0 × 10⁻⁹; black vs. light grey: p = 1.5 × 10⁻⁸). For scale, every wolf the team tested carried exactly two copies — the low end of the range in dogs of any colour — which places the higher copy numbers as something domestic dogs accumulated, not an ancestral trait.

The red-side finding already appears in brief on this site's red intensity article; this piece exists because the black and grey side of the same study has not been covered anywhere on the site, and it is worth doing carefully rather than in passing.

What "Light Grey" Meant in This Study — Read This Part

This is the section that matters most, and it is the reason this article is filed as emerging evidence rather than folded into the established D-locus or G-locus pages.

The poodles in this study were sorted into colour groups by owner-reported colour only. The paper does not report genotyping any of the poodles at the D locus (dilution) or controlling in any way for progressive greying, the mechanism covered in depth in the G-locus article. That means the "light grey / silver" group of 22 poodles was, almost certainly, a mix of dogs that arrived at a pale coat by completely different, already-understood routes:

• True blues (dd), born pale and never black at any point.
• Cleared blues and silvers (Gg or GG), born black and greying with age by the mechanism this site already documents in detail.
• Possibly some dogs that are none of the above — just naturally toward the paler end of black, which is the very thing this KITLG variant might explain.

A study that does not separate those groups cannot tell you which of them the CNV effect belongs to, or whether it is doing something in addition to dilution and greying rather than in place of them. The honest reading is that KITLG copy number is a real, independently significant signal on colour depth, and it is very likely one more thread in a rope that already includes the D locus and the (still genetically unidentified) G locus, not a rival explanation for any of them.

It Is Not Universal Across Breeds

The same study looked for the same association in Golden Retrievers and yellow Labrador Retrievers, two more phaeomelanin-based breeds, and found nothing: no significant correlation between copy number and shade in either (p = 0.9977 and p = 0.7377). The authors' own conclusion is that "there are still additional pigment intensity loci or variants to be identified" — this variant explains part of the picture in the breeds where it was found to matter, poodles among them, and evidently none of the picture in some others.

That inconsistency is itself informative. It is further evidence that coat intensity is genuinely polygenic, the position this site's red intensity article already takes: several genes of partial effect, weighted differently breed to breed, rather than one master dial that works the same way everywhere.

The researchers also excluded cream dogs that were homozygous for a separate, already-identified pheomelanin gene, MFSD12, specifically so that gene's effect would not be mistaken for KITLG's. That is a good methodological sign: it means the KITLG signal reported here is not an artefact of a different, already-known intensity gene riding along in the same dogs.

What This Means for a Breeder Today: Nothing Actionable Yet

This is a genuinely interesting result and it is not a tool. As of this study, and as of this article:

• No commercial lab tests this variant. It is a research finding from one paper, measured by a specialised lab technique (digital droplet PCR), not a line item on any DNA panel a breeder can order.
• Even where the signal is real, it is a trend across groups, not a per-dog prediction. The paper reports median copy numbers, not the full spread within each colour group, so there is no way to say from this data alone how much overlap exists between, say, a deep black and a middling one.
• It cannot be reduced to a genotype and it will not appear in the calculator. Colour depth on this site is handled exactly as it always has been: red-spectrum shade and greying status are recorded from the dog, not guessed from a test result, because that is what the evidence currently supports doing.

The Honest Bottom Line

A single regulatory variant near KITLG tracks, with strong statistical significance, with how deep a poodle's pigment runs — on the red side and the black side both — and the effect looks like a genuine, evolutionarily interesting piece of domestication biology: wolves sit at the low end of the dial; dogs, poodles very much included, have drifted toward more copies and more intense colour. That is worth knowing.

What it is not, yet, is a test, a mechanism for silver or blue, or a reason to change anything about how this site or its calculator handles intensity, dilution, or greying. Depth of colour looks to be the sum of several genes working together, KITLG among them, on top of whichever base colour and clearing mechanism a dog already has — which is exactly why watching the adult dog remains the only reliable way to know what you are actually working with.

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See also: Why Red Poodles Fade for the phaeomelanin-side breeding practices this same intensity variable drives, and What Is the Graying Gene? for the D-locus and G-locus mechanics this article deliberately does not replace.