The mighty genome editor CRISPR isn’t so powerful in lizards and snakes: Never before has it been used to edit the embryos of these reptiles. Now, researchers have come up with a workaround—by editing the immature, unfertilized eggs of brown anole lizards.
Researchers typically edit with CRISPR by injecting it into a single-celled fertilized egg, creating a DNA change that is present in all subsequent cells. But female anoles are a special challenge: They store sperm in their oviducts for long periods, making it difficult to time the introduction of CRISPR to fertilization. They also form eggshells at fertilization, and it’s extremely difficult to insert a needle at that stage without damaging the embryo.
So researchers from the University of Georgia (UGA) in Athens instead injected the CRISPR complex into immature eggs still in the ovaries, targeting a gene that produces tyrosinase, an enzyme that affects pigmentation. After altering 146 immature eggs from 21 lizards, the scientists got their payoff: four albino offspring, they report in a preprint posted this week on bioRxiv. To produce the change in coloration, both maternal and paternal genes must have mutated, making the researchers suspect that CRISPR edited the egg genes and then stuck around, crippling the paternal genes after fertilization.
The new technique, which the scientists say will likely work in many other lizard and snake species, “is a game changer,” tweeted Tony Gamble, an evolutionary biologist who studies geckos at Marquette University in Milwaukee, Wisconsin. UGA’s Douglas Menke, the mouse developmental geneticist who led the experiment, was more to the point: “The whole field of developmental genetics has left reptiles in the dust.” Until now.