Genetics Allow Animals to Produce their Own Sunscreen

Researchers have discovered that unique genome sequences allow fish, reptiles, birds and other animals to create a compound that acts as sunscreen.

The compound, called gadusol, naturally protects the animals from ultra-violet rays and acts as an antioxidant. Professor Taifo Mahmud of the Oregon State University College of Pharmacy, the lead author of the study, said his team was initially studying genes in bacteria while trying to synthesize other compounds.

“We have been working on the bio-synthesis of natural products in bacteria,” Mahmud said. “We wanted to understand how bacteria makes the compounds, so we are looking at the genomes, the genes and the proteins in the bacteria that are involved in making those compounds. Initially, we thought the genes were only in bacteria. Recently we have discovered the same genes present in animal genomes.”

While the discovery was surprising, gadusol is not a new compound. Scientists have found it in fish and fish eggs before, but previously believed they acquired it through their diets. Gadusol is found in algae and other organisms.

“Gadusol itself is not a new compound,” Mahmud said. “It’s been found before in fish eggs and in many different fish, but because gadusol and related compounds have been found to be produced by cyanobacteria and many marine microorganisms, the notion was that gadusol was not produced by fish but acquired by them through their diets.”

Mahmud said it’s likely the presence of the genes that make the compound goes back to early vertebrates and that evolution likely played a role in their presence.

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“If you look at animals before vertebrates, they do not have the genes,” Mahmud said. “The genes were probably introduced with the ancestral vertebrates and bony fish. We also found that different algae have the genes that can make gadusol which are very similar to those in the fish. The hypothesis now is that the origin of the genes in the animals comes from the algae through horizontal gene transfer.”

Humans and other mammals do not have the genes to produce gadusol, although Mahmud said there is an indication that they were once part of their genetic codes.

“Mammals do not have the gene, so apparently sometime during evolution, they lost them,” Mahmud said. “These genes are flanked by several other genes and in mammals only the two genes that make gadusol are missing, the others are still there in that area of the genome. Somehow, the gene has been deleted.”

Mahmud’s team used zebra fish for their research, but compared the genome sequence to those in other animals.

“We extracted the compound from zebra fish embryos and we found gadusol,” Mahmud said. “We looked at other genome sequences from birds and reptiles and all of them have the same set of genes suggesting all those animals are also able to produce gadusol.”

Gadusol has been used in the past in anti-aging products and has also been proven to block ultraviolet rays. It is also an antioxidant, and Mahmud said it might have other uses, including as a cancer fighting drug.

“People have been using it for anti-aging purposes and as a sunscreen,” Mahmud said. “It can also be used as an antioxidant because the compound has very good antioxidant properties. It could be a good cancer preventive agent. Because animals can produce this compound, it is presumably not toxic and quite safe.”