For the first time ever, scientists have created genetically modified snakes. The CRISPR-edited reptiles are providing new insight into how corn snakes (Pantherophis guttatus) develop their precisely patterned scales.
Much like feathers on birds or hairs on mammals, snake scales are the result of placodes — small, thickened structures on the skin that develop at the embryonic level, according to a new study published Wednesday (June 14) in the journal Sciences Advances.
But unlike most other species including mice, where the placodes are random, a snake's placodes develop in a highly organized fashion, laying out the positioning of every single scale. Rather, the spatial organization of these placodes follows a pattern in nature first explained by mathematician Alan Turing, the researchers added.
Scientists from Geneva wanted to know exactly how and why these "near-perfect hexagonal pattern[s]" developed on the dorsal scales located on the snakes' backs and flanks, but not on the ventral scales that form as a single row on the animals' underbellies.
The researchers found that an embryo's ventral scales develop first and align with the position of somites — blocks of cells that determine the location of the vertebrae, ribs, muscles and dermis of the skin. Once the ventral scales are established, two separate "waves" of placodes develop, traveling toward each other.
The waves meet laterally, creating the tidy hexagonal patterns that are the hallmark of a snake's skin, according to a statement.
Related: Scientists changed scales on chicken feet to feathers by tweaking a single gene
"To confirm our work, we used computer simulations and received similar results," lead author Athanasia Tzika, a postdoctoral fellow in the Department of Genetics and Evolution at the University of Geneva, told Live Science. "This is surprising because the pathway is essential for proper development of skin appendages in birds, reptiles and mammals."
Tzika pointed to lizards with a mutated EDA gene, which were previously studied in her university's lab, as an example of a reptile that never developed scales.
This led researchers to create the world's first genetically modified snakes. Using CRISPR-Cas9, which edits genes by severing the DNA and letting the natural DNA repair itself, Tzika and her team successfully created "mutant" snakes that lacked dorsal-lateral (hexagonal) scales, but still had ventral scales.
She said that this proved that the scales aren't "self-organizing" and occur "without a functional canonical EDA pathway."
In total, the scientists created four corn snakes, all of which are currently two years of age and "are doing well," Tzika said.
"The animals we produced are exactly the same as the naturally occurring snakes; we were able to reproduce the same phenotype," Tzika said.
She said they plan to conduct another round of CRISPR edits on the genetically modified snakes in two years, once they reach sexual maturity, "to see if the mutation will transmit to the next generation."
