What Lil Bub’s Genetic Mutations Show About Her Lineage

Lil Bub, the second hardest working feline in the game (respect to Grumpy Cat), is in the process of getting her genome analyzed. A team of geneticists from the Max Planck Institute for Molecular Genetics in Berlin has taken a small sample of Bub’s blood — science, like Internet fame, has its costs — in an effort to suss out the source of her mutations.

Bub’s numerous unusual characteristics (and a great marketing team) are the reason for her 1.9 million Facebook followers: “She has extra digits on every paw, no teeth and a short snout, which is why her tongue hangs out,” the researchers wrote on their campaign to crowdfund the experiment. “Also, her skeleton produces too much bone tissue, a rare disease known as osteopetrosis.”

The German molecular geneticists haven’t delved terribly deep into Bub’s genome — only 0.00023 percent of a complete genome sequence so far, according to the scientists’ Reddit AMA — but within that tiny percentage, the scientists have already shed light into Bub’s DNA and ancestry. Bub has a tiny genetic quirk, a point mutation, in what’s called the zone of polarizing regulatory sequence (ZRS). A mutated ZRS causes the signaling protein known as Sonic Hedgehog, which controls the formation of embryonic limbs, to express in areas where it normally wouldn’t.

Ernest Hemingway’s cats famously had a similar ZRS mutation as Lil Bub's, resulting in added toes. But Lil Bub is even odder than Hemingway’s cats. “She has additional digits on ALL paws, whereas Hemingway cats are typically only polydactyl on 2,” the scientists wrote on Reddit. “We hope we can answer [how closely Bub and Hemingway’s cats are related] with the whole genome sequencing.”