Genetically Modified Sex Selection Could Save Rats

Hayden Katz Animals /
mice rat lab animal
Marcos del Mazo Contributor via Getty Images

Scientists have found a way to decide the sex of mice through gene editing. Each year, thousands of rodents are experimented on. Researchers in England have found a way to rescue that number. The procedure is explained in Nature Communications, an academic journal.

mice lab rats experiment
China Photos / Stringer via Getty Images

In the first stage, the research team takes two mice, one with female chromosomes and another with male chromosomes. Next, a gene-editing molecule, Crispr-Cas9, is split in two and given to each participant. In the XX rodent, the molecule is inserted in the DNA, and for the XY mice, the gene editor is placed in either the Y or X chromosome. The outcome is presented after the mice mate with one another.

rat mice research genes
China Photos / Stringer via Getty Images

The decision of whether the gene modifier is placed in the father's X or Y chromosome is based on which sex was needed. If Crispr-Cas9 is put in Y, then that chromosome won't be activated, producing a female-only litter. The female fetuses mature regularly, but the male embryos end up having both parts of the gene-editing molecule, so they don't develop. This process is vice-versa, if the deactivating gene is found in the male X, then only XY fetuses will develop normally. Since gender is defined by the sex chromosome, the scientists were able to manipulate the genes to create an outcome they desired. By making the gene inactive, the offspring ceased developing past the point of having around 16 to 32 cells.

genetically modified baby mice
Smith Collection/Gado / Contributor via Getty Images

This technique could potentially save the lives of millions of rodents since most research needs specifically require either male or female mice. "The numbers of mice used in each case obviously varies," explained Dr. James Turner, who works at Londons' Francis Crick Institute, "but the total mouse usage would easily be in the hundreds of thousands. This work could have immediate and valuable impact in scientific laboratories." Peter Stevenson, the chief policy adviser at Compassion in World Farming agreed with research, "We support its use to improve animal welfare, such as ensuring that hens only produce female chicks, as this would prevent the killing of millions of unwanted male chicks in the UK each year. "But, the scientists aren't finished just yet, more research needs to be conducted before gene editing molecules can be used on lab animals."