Ball pythons shed new light on reptile coloration

Most of the research on skin coloration and patterning in vertebrates has been conducted on laboratory mice. However, since mice don’t share all of the same kinds of color-producing cells (known as chromatophores) with other vertebrates, there are limits to what mice can tell us about coloration in reptiles such as snakes, for instance. 

Now, by combining techniques such as whole gene sequencing, gene-editing, and electron microscopy, a team of researchers from McGill University in Canada has examined color variations and patterning in the skin shed by ball pythons (Python regius) bred in captivity. The analysis revealed that a particular gene (tfec) plays a crucial role these snakes’ pigmentation, more specifically in a classic color variant found across vertebrates and distinguished by blotches of white (the so-called “piebald coloration”).

The captive-bred reptile industry is currently booming, with over 4.5 million households in the U.S. alone keeping reptiles. Due to the spectacular color variations produced through captive breeding, a single ball python can now sell for tens of thousands of dollars.

“Ball pythons show incredible variation in skin coloring and patterning, which is part of their appeal for hobbyists, but also makes them really useful for researchers who want to understand the genetic basis of coloration,” said study senior author Rowan Barrett, an expert in Biodiversity Science at McGill.

“The pet trade has created a huge pool of color variation that would not have existed otherwise. This provides a catalogue for us to figure out the many ways that genes produce the amazing diversity of colors, spots, and stripes we see across different animals.”

In order to identify the genes responsible for particular traits, scientists usually examine genetic variants that are present in the animals that have the traits, and absent in those that don’t have them. By using shed skin samples collected from snake breeders, the researchers discovered that piebald snakes carried the same mutation in a gene called tfec.

However, since finding a correlation between a specific gene and a particular trait does not necessarily imply causation, the scientists used the genetic-editing technique CRISPR to modify this gene in a different species of reptile, the brown anole lizard. This intervention revealed that genetically modified lizards do indeed show altered coloration, thus proving that mutations to tfec cause changes to color-producing cells.

“Our research advances knowledge of the genetics of vertebrate coloration generally and particularly of the development of iridescent cells, which haven’t been studied as much as other color pathways,” said study lead author Alan Garcia-Elfring, a PhD student in Biology at McGill.

“It also highlights the potential benefits of working with non-academic communities like ball python breeders to accelerate discoveries in fundamental science. Our job, at this point, is to figure out what other mutations underlie all this variation seen in captivity, and how these mutations interact. It’s an exciting time for both researchers and reptile hobbyists.”

The study is published in the journal Current Biology.

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By Andrei Ionescu, Earth.com Staff Writer

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