Thank this gene mutation for this endearing feline feature

Analysis by Dr. Karen Shaw Becker

Story at-a-glance -

  • Cats who appear to be wearing socks, or tuxedos, have piebaldism, a gene mutation that causes unusual patterns of pigmentation
  • Research suggests piebald patterning is the result of a process that occurs before birth featuring pigment cells that don't divide often enough to create a monochrome coat
  • There are several different bicolor patterns, including the tuxedo, the cow, and the cap and saddle
  • Other gene mutations influence the appearance of tabby cats, the Norwegian Forest cat, and the Siamese and Burmese breeds

Arguably one of the most endearing features of some kitties, including the famous (and infamous) online sensations Lil Bub, Maru and Grumpy Cat (RIP), is their adorable white paws that make them look as if they’re wearing socks. The technical term for those socks (aka mittens, booties, tuxedo) is piebaldism, which is a result of a mutation in the KIT gene that causes an unusual distribution of the cells (called melanocytes) that give eyes, skin and hair or fur pigment.

Other well-known piebald kitties include Mr. Mistoffelees, the tuxedo cat in the musical “Cats”; cartoon cats Tom of “Tom and Jerry”, Felix the Cat, Kitty Softpaws of “Puss in Boots” (the Shrek spin-off), Sebastian from “Josie and the Pussycats” and Sylvester; Dr. Seuss’s “Cat in the Hat”; the Clinton family’s Socks, who lived in the White House from 1993 to 2001; and Humphrey, the black-and-white “Chief Mouser” at 10 Downing Street, the official residence of the U.K. Prime Minister, for 18 years. Here’s how kitties with socks come to be, from the online magazine Popular Science:

“When a cat is still an embryo, all of its available melanocytes are bunched up toward its back, where its spinal column will eventually form. As the fetus develops into a mewling kitten, pigment cells spread throughout the developing body.

If the melanocytes are evenly distributed, the cat could have a unicolor coat, like Sabrina the Teenage Witch's all-black cat, Salem, or the all-white Hello Kitty. But in many animals, the cells spread irregularly. That's how you get a cat like Sylvester, who's black from his back to his legs, but white down to his toes.”1

The word "piebald" is a combination of “pie” (from “magpie”), and “bald,” which means a white patch or spot. It refers to the distinctive black-and-white plumage of the magpie. In addition to cats, other animals with piebaldism include horses, dogs, birds, pigs, cattle and even some snakes.

Pigment cells in piebald animals don't divide often enough to create a monochrome coat

Results of a 2016 study suggest that scientists have discovered the way in which piebald patches in black and white cats are formed during gestation.2 According to ScienceDaily:

“Researchers who set out to learn how pigment cells behave in mice found that they move and multiply randomly during early development rather than follow instructions. Their findings contradict the existing theory that piebald patterns form on animals' coats because pigment cells move too slowly to reach all parts of the embryo before it is fully formed.”3

Professor Ian Jackson, Ph.D., of the University of Edinburgh and study co-author offers this explanation:

“The black and white cat has a mutation and it was assumed that because we knew those cells moved through the skin, it was because the cells didn’t move fast enough, but what we have shown is actually the cells move faster in the black and white cat or spotted mice.

The problem is there’s not enough of them so they don’t divide enough, they divide more slowly. It was always imagined that there would be a signal that would tell them where to go, but they just move at random. It’s like diffusion — if you put a drop of milk in a cup of coffee that milk spreads through the whole cup of coffee. Eventually the cells spread through the skin.”4

The mathematical model used by the Universities of Bath and Edinburgh scientists may have application in other research to track different cells during early development. Their study results could potentially shed light on medical conditions that develop in utero, for example, holes in the heart.

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Other gene mutations that influence animal coat colors

According to Popular Science, tabby cat coats — which feature distinctive stripes, dots, lines or swirling patterns and a mark resembling an “M” on the forehead — are the result of the agouti gene, which programs the distribution of black pigment. This same gene is responsible for bay horses with their brown bodies and black manes, tails, ear edges and lower legs.

The Norwegian Forest cat has two gene mutations affecting the coat. The orange gene on the X chromosome produces a red coat in some kitties, and an alteration on the MC1R gene causes the breed to have one coat color at birth that morphs into a golden or amber color as the cat matures.

The Burmese and Siamese breeds have a form of selective albinism that allows their bodies to suppress melanin production based on temperature.

Piebald patterns

Kitties with piebaldism are found across several different breeds, from American Shorthairs to Turkish Vans. There are several commonly seen piebald patterns, including the following:

Tuxedo pattern — This is a predominantly black cat with white markings on the chest, tummy, paw and sometimes the chin and/or nose.

Mask-and-mantle pattern A cat with a black back, shoulders and head, and a white underside.

Cap and saddle pattern A cat with black over the top of the head, white shoulders, and a large black patch on the lower back, near the tail.

Locket pattern — A black cat with one small white patch on the chest or tummy.

Cow pattern A predominantly white cat with black spots or patches on the torso.

Van pattern A white cat with black markings on the head and tail only.

Piebald personalities

Whether the color of a cat’s fur influences his personality is a subject of much debate, and there has been no shortage of opinions offered over the years. In an 1895 book titled “The Cat”, author R.S. Huidekoper wrote the following about bicolor cats:

“It tends more than any other cat to be come fat and indolent, or ragged and wretched, as the case may be. […] The Black and White cat is affectionate and cleanly, but it is a selfish animal, and is not one for children to play with.”5

A study in Bavaria suggests that black and black-and-white cats tend to wander further from home than cats of other coat colors. The study involved a large geographical area, which suggests the tendency may have a genetic basis.6

According to Sarah Hartwell of Messybeast, while most cat color/personality reports are anecdotal, there have been studies in which owners or veterinarians were asked to associate particular colors with particular personality traits.7 The study participants reported that black-and-white Persians were “placid,” black-and-white British Shorthairs were “even-tempered and friendly” and black-and-white mixed breeds were “wanderers.”

In 1973, in a Pedigree Pet Foods book called “Your Guide to Cats & Kittens”, the author asserts that black-and-white Persians are “excellent ratters and mousers.”8 Early in the 21st century, George Ware, a British boarding cattery owner offered his own theory of colors and temperaments. Based on personal experience, Ware suggested that black-and-white cats are:

“True lap cats. Very loyal to their family, especially to a particular family member. Liable to be moody.”9