Scientists produce world's first gene-edited reptiles

Aug. 28 (UPI) -- For the first time, researchers have used the gene-editing technology CRISPR-Cas9 to produce mutant reptiles, four tiny albino lizards.

Scientists have previously manipulated the genes of mammals, birds, fish and amphibians, but never reptiles. The team of University of Georgia researchers described their breakthrough in a paper published this week in the journal Cell Reports.

"Reptiles are very understudied in terms of their reproductive biology and embryonic development," Douglas Menke, study co-author and an associate professor in the department of genetics at Georgia, said in a news release. "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."

To produce mutant offspring, scientists inject a gene-editing solution into a newly fertilized egg or single-cell embryo. The early intervention allows the gene-edit to be reproduced in all subsequent cells as the stem cells divide, multiply and differentiate.

Because female reptiles can store sperm in their oviducts for long periods of time, predicting when they will fertilize their eggs is difficult. The unpredictability of reptile egg fertilization made it difficult to properly deploy CRISPR-Cas9.

Menke and his colleagues were able to sidestep the hurdle by micro-injecting CRISPR proteins into multiple immature eggs inside the lizard's ovaries. Scientists injected a solution targeting the tyrosinase gene into 146 oocytes inside 21 female brown anoles, a common lizard species in the Caribbean.

Researchers waited for the eggs to be fertilized, laid and hatched to see if the effort was a success. Four weeks later, out came four lizards with albinism.

"When I saw our first albino hatchling, it was truly awe inspiring," said Ashley Rasys, a doctoral student and the study's first author. "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."

One of the reasons scientists chose to study albinism in brown anoles is that the condition is linked with vision problems in humans. The tyrosinase gene is known to control some aspects of eye development in humans and lizards, but not in more common animal models like mice. In followup studies, scientists plan to study the effects of tyrosinase gene manipulation on the development of the retina.

"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," said David Lee, vice president for research at Georgia. "I applaud Dr. Menke and his colleagues on this very significant achievement."