While they are often referred to as brown chameleons, the University of Georgia lab now has four gene-edited Anolis sagrei chameleon lizards that appear pale pink. They are albinos, which is said to be the result of the world's first successful production of genetically modified reptiles. The study could have implications for human medicine.
One of four albinos, and an unmodified example (Source: University of Georgia)
Chief scientist Douglas Menke chose the brown chameleon lizard for the study because on various islands in the Caribbean, isolated lizard populations are known for their unique traits that develop independently. However, genetically modifying any type of reptile presents some challenges.
Typically, when utilizing CRISPR gene editing tools, scientists inject gene editing solutions into freshly fertilized eggs or single-cell embryos of animals. This leads to mutations in the DNA, which are reproduced in all subsequently developing cells.
In reptiles, however, females are able to store sperm in their fallopian tubes for long periods of time after mating — which makes it difficult to determine when egg fertilization actually occurred. In addition, once the egg is fertilized, its flexible shell and lack of internal air space make it difficult to manipulate the embryo without damaging it.
To address these challenges, Menke and colleagues used the CRISPR-Cas9 tool to microinject the CRISPR protein into immature eggs (aka oocytes) that are still located in the anoles ovary. Then they just wait for those eggs to fertilize naturally. All told, the scientists injected 146 eggs into 21 species of reptiles, targeting the tyrosinase gene — which, when inactivated, produces albinism. A few weeks later, the end result was four pink lizards.
PhD student Ashley Rasys, one of the anoles, as an interesting side note, shows tyrosinase manipulated from copies of genes inherited from mothers and fathers. According to the scientists' research, this suggests that crispr proteins are more active in the mother than expected, mutating the paternal gene after fertilization occurs.
"It was a surprise," Menke said. "It allows us to see the functional needs of genes without having to reproduce mutated animals to produce offspring that inherit mutated genes from their parents." Significant time savings. ”
In addition, the study could improve treatments for eye diseases in humans. Although tyrosinase is necessary for human and eye development, it is not present in commonly studied animals such as mice. Now, it is possible to use analles for eye health research.