A California pet shop began breeding Mr. Frosty, one of the hundreds of "Lemon Frost" Leopard Geckos that has since spiked in popularity and in price - and scientists have discovered where these lizards got their bright and unusual pigmentation.
Mr. Frosty, as he was known to the geneticists from the University of California, Los Angeles (UCLA), was characterized by bright yellow bands striping down his back, with white speckled skin painting its head and tails. After the leopard gecko was examined through a variety of genetic analyses, researchers discovered that the speckles and the pigmentation in Mr. Frosty were adapted from a gene associated with skin cutaneous melanoma, a form of cancer in skin cells often fatal for humans.
The researchers present their findings of the origin of the brightly-colored leopard geckos in the article "Genetics of white color and iridophoroma in "Lemon Frost" leopard geckos," published in the latest PLOS Genetics journal.
Breeding Leopard Geckos with Cancer Genes
In the same report, researchers disclose that the California pet shop that bred and sold Mr. Frosty began breeding the Lemon Frost Leopard Geckos back in 2016. The "Lemon Frost" was one of the available color variants, named after the spots colored like the popular citrus fruit.
However, the bred lizards had one flaw: almost four in every five of them develop white skin tumors from their first five years of life. Furthermore, some of the leopard geckos grow abnormally large cancer tumors that hinder their movement and could even expose them to infection if injured or ruptured. Researchers initially suspected that this trait was probably genetic in nature, probably a mutation in one of their genes.
"To identify the genetic basis of this trait in reptiles is really marvelous," says Douglas Menke, a developmental geneticist from the University of Georgia who was not a part of the recent work, in a news release from the Howard Hughes Medical Institute. Menke additionally explains that genetic studies in reptiles are not usual, and those that are biomedical in nature are even more so. He hopes that a reptile species, like leopard geckos, will become a staple model for scientific studies in the same way mice and zebrafishes are used today.
The leopard geckos have colorful names, in the same manner, that Mr. Frosty is of the Lemon Frost variety: Sunburst Tangerine, Granite Snow, Black Night, and more. However, scientists who saw them still didn't know the genetics that led to these colorful variants.
Understanding Genetic Predispositions Toward Bright Colors
Many brightly colored animals like fishes, birds, chameleons, and leopard geckos come from a special type of cell called iridophores. These cells produce their vibrant colors through small crystals embedded in them, with their shapes and structures affecting how they receive, bend, and reflect light to create a variety of vivid colors. Meanwhile, human skin cells get their natural color from melanin, a chemical pigment.
Researchers collected some 500 DNA samples from the leopard geckos and sequenced their genomes, looking for particular regions that might be responsible for their unique pigmentations and should be unique to their species.
They then found a single gene, called SPINT1, which has been previously linked to cancer in humans and animals. The improper development or lack of the SPINT1 gene has been known to cause tumors in mice and zebrafish.
Researchers are now planning to pursue the study but with two specific variants related to Mr. Frosty: the Blizzard and the Patternless - with the two prospective variants lacking colors and patterns.
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