Scientists have created the world’s first genetically modified reptiles – four adorably tiny albino lizards. The achievement is a gene-editing breakthrough that could have applications for both reptile biology and human medicine.
To produce the little albino lizards, the team employed the CRISPR-Cas9 gene-editing tool, which has been used for all sorts of things from treating a rare blood disorder to making corals more resilient to climate change.
Until now, modifying reptiles using CRISPR has posed a bit of a challenge. Normally, when scientists use the technique to genetically modify an animal, they inject gene-editing solutions into a single-celled embryo or an egg that’s just been fertilized. This causes a mutation in the DNA, which is then present in all new cells produced as the embryo develops.
However, reptilian embryos make things a bit more complicated. Female reptiles have the ability to store sperm in their oviducts (the tube an egg passes through when it leaves the ovary) for long periods of time. This makes it tricky for scientists to know when an egg has been fertilized. What’s more, the fertilized eggs of reptiles have no air space inside, making it difficult to insert anything without damaging them.
“Reptiles are very understudied in terms of their reproductive biology and embryonic development,” University of Georgia (UGA) geneticist Douglas Menke said in a statement. “There are no good methods to manipulate embryos like we can easily do with mammals, fish or amphibians. To our knowledge, no other lab in the world has produced a genetically altered reptile.”
The lizards used in the study were brown anoles (Anolis sagrei), which, according to Menke, are the reptilian equivalent of the Galapagos finches made famous by Darwin. The anoles are found across the Caribbean islands, with unique adaptations evolving dependant on their habitats, such as running vs climbing legs.
Cleverly, the team managed to insert CRISPR proteins into immature unfertilized eggs within female lizards’ ovaries. This modified the genes received from the mother and, to the researchers’ surprise, the father too. It seems the CRISPR solution remained active longer than expected, changing the genetic makeup of both the egg and then the sperm when fertilization took place.
Specifically, the researchers modified the tyrosinase gene. When this gene is inactive, albinism occurs. They managed to inject 146 immature eggs from 21 lizards before natural fertilization took place. When the baby lizards hatched, the team discovered their experiment had worked. Among the characteristically brown critters were four distinctive pale pink ones.
“When I saw our first albino hatchling, it was truly awe-inspiring,” said first author Ashley Rasys. “I’m most excited about the possibility of expanding this approach into many other reptilian model systems, effectively opening the doorway for future functional studies.”
The albino lizards could inform scientists working on human eye health. The tyrosinase gene is involved in eye development, both humans and anoles have it, but creatures like mice that we use as model organisms do not. The findings are currently awaiting peer review, but you can view them on the pre-print server bioRxiv.
“This work could have far-reaching impact not only for the study of reptile genetics but also for the advancement of genomic medicine and application in humans,” David Lee, UGA vice president for research, explained.
2
