![]() ![]() In 1953, one amelanistic snake from North Carolina was incorporated into a small captive-breeding population and subsequent crosses demonstrated that the trait is determined by a single-locus recessive mutation 28, 29, 30. As they entirely lack black pigment, amelanistic corn snakes also exhibit pink eyes and do not show the characteristic black checkers on their ventral scales ( Fig. Amelanistic corn snakes exhibit a normal pattern of orange dorsal saddles and lateral blotches (made of uncharacterised pigments), but the black borders around these marks are replaced with white skin ( Fig. Amelanism is expected to be genetically heterogenous and may reflect mutations at different loci with a key role in melanogenesis as well as different rare mutations at the individual loci. Amelanism is the oldest colour trait variant to have been noticed in corn snakes 27 and it has been observed in Florida, North Carolina and Tennessee 28. Indeed, corn snakes are oviparous, harmless and sufficiently small (generally <1.5 m) to be easily maintained and bred in captivity and they exhibit multiple colour morphs, enabling systematic analysis of the molecular pathways controlling adaptive colour (and colour pattern) variation in reptiles.Īs in many other lineages 16, 17, 18, 19, 20, 21, 22, 23, melanin-based coloration in squamates is highly variable and likely plays crucial roles in thermoregulation, camouflage, UV protection and sexual selection (e.g. ![]() We are promoting the corn snake ( Pantherophis guttatus), a Colubridae species from the southestern United States of America, as an ideal snake model for evolutionary developmental studies 12, 13, 14, 15. Colour polymorphisms in squamates have been used as examples of adaptive evolution associated with habitat, behaviour, reproductive strategies, ageing, immune response and speciation 8, 9, 10, 11. Squamates (lizards and snakes) exhibit a remarkable set of pigmentary and structural elements generating a broad variety of colours and colour patterns ( e.g. ![]() Vertebrate skin coloration provides an effective model system for exploring the genetic determinism and developmental plasticity associated with phenotypic variation. Understanding the determinism of trait diversification is a key theme in evolutionary biology in general and evolutionary developmental biology (EvoDevo) in particular. In combination with research in the zebrafish, this work opens the perspective of using corn snake colour and pattern variants to investigate the generative processes of skin colour patterning shared among major vertebrate lineages. As amelanistic snakes exhibit white, instead of black, borders around an otherwise normal pattern of dorsal orange saddles and lateral blotches, our results indicate that melanocytes lacking melanin are able to participate to the normal patterning of other colours in the skin. Proceeding with sequencing the candidate gene OCA2 in the uncovered genomic interval, we identify that the insertion of an LTR-retrotransposon in its 11 th intron results in a considerable truncation of the p protein and likely constitutes the causal mutation of amelanism in corn snakes. Using our captive-bred colony of corn snakes, transcriptomic and genomic next-generation sequencing, exome assembly and genotyping of SNPs in multiple families, we delimit the genomic interval bearing the causal mutation of amelanism, the oldest colour variant observed in that species. The corn snake ( Pantherophis guttatus) is a new model species particularly appropriate for investigating the processes generating colours in reptiles because numerous colour and pattern mutants have been isolated in the last five decades. ![]()
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