The Code That Turns Corn Snakes into Masterpieces

In many animals, skin color and patterns play crucial roles in camouflage, communication, and temperature regulation. Corn snakes, for example, exhibit various morphs with bright colors like red, yellow, or pink, and their dorsal spots may merge or form stripes. But what genetic and cellular processes drive these striking patterns? A team from the University of Geneva (UNIGE) has pinpointed a key factor: a single gene, CLCN2. Their research, published in Genome Biology, sheds new light on the genetic control and evolution of animal coloration.

The Role of Chromatophores in Shaping Corn Snake Skin Colors and Patterns

Corn snake skin colors and patterns result from the arrangement of chromatophores—cells containing pigments or light-reflecting crystals. Typically, they have red blotches outlined in black on an orange back and a black-and-white checkered belly. However, various morphs can exhibit a broad range of colors and patterns.

Two commonly seen morphs are the Motley and Stripe varieties. In the Motley morph, the typical dorsal spots are fused or fragmented, creating a more linear design. In the Stripe morph, continuous longitudinal stripes run along the snake’s back. Despite their differences, both morphs share a notable feature: their bellies are solid-colored, lacking the usual checkered pattern.

Uncovering the Genetic Basis of Corn Snake Coloration: The Role of CLCN2

A team led by Athanasia Tzika and Michel Milinkovitch at the University of Geneva studied the genetic basis of corn snake patterns. By breeding Motley and Stripe morphs and sequencing their offspring’s genomes, they discovered both are linked to mutations in the CLCN2 gene. This gene encodes a protein that forms a chloride ion channel in the cell membrane. The movement of chloride ions across the membrane creates an electrical potential, enabling cellular signals to be transmitted.

In Motley snakes, the variation arises not from a mutation in the gene itself but from a significant reduction in its expression. In Stripe snakes, however, a small DNA segment—a transposon—is inserted into the CLCN2 gene, rendering the protein non-functional.

“These findings were unexpected, as in humans and mice, the CLCN2 channel is crucial for neuronal activity, and mutations in this gene are linked to severe conditions like leukoencephalopathy, a disorder affecting the brain’s white matter,” explain Sophie Montandon and Pierre Beaudier, researchers in the Milinkovitch/Tzika lab and co-first authors of the study. “To further investigate, we conducted genetic experiments in corn snakes to deactivate the CLCN2 gene. The resulting mutants displayed the Stripe phenotype, confirming the gene’s role.”

Exploring the Role of CLCN2 in Corn Snake Coloration and Development

To understand CLCN2’s role, scientists analyzed its expression in corn snakes. They found it expressed in the brain and chromatophores during development. In mutants, chromatophores failed to aggregate properly, disrupting the typical color blotches. Instead, they organized into stripes, as observed in Stripe individuals.

“Our findings show that a mutation in the CLCN2 gene in corn snakes does not lead to neurological or behavioral issues. However, the protein plays a crucial and previously unrecognized role in the development of skin coloration patterns,” concludes Asier Ullate-Agote, co-first author of the study.

Investigating the Role of CLCN2 in Chromatophore Function and Coloration Patterns

The next phase of the research will aim to understand the role of the CLCN2 chloride ion channel in chromatophore membranes, specifically how it affects interactions between pigmented cells. The objective is to uncover the cellular mechanisms responsible for the wide variety of coloration patterns seen not just in corn snakes, but also in other reptiles.

Read the original article on: Scitech Daily

Read more: AI-Designed Proteins May Offer Protection Against Lethal Snake Venom