Ancient mutation helped create delicious, fatty pork. Scientists just fixed it
Of all the frights you might experience between now and Halloween, this one might be the worst: Chinese scientists have genetically engineered pigs to be reduced-fat.
They meant well.
The engineering created hardier, leaner pigs that the scientists argue will improve pig welfare and cut losses and energy use on farms. Publishing data on their genetically modified pigs in PNAS, the scientists don’t mention anything about how the new pigs will taste.
The researchers got the idea for the genetic correction—or travesty, depending on your perspective—by noting a common problem in the pig industry:
Modern pigs struggle with poor thermoregulation, leading to significant neonatal mortality of piglets caused by cold stress at birth. This is a major welfare and energy expenditure issue for the swine industry in cold regions worldwide.
They speculated that the genetic root of the problem was the lack of a metabolic gene called uncoupling protein 1, or UCP1. This gene is involved in a process that lets energy—in the way of fat—get burned up to generate heat. Ancestral swine lost the gene about 20 million years ago while they were hamming it up in tropical and subtropical digs. The loss led modern piggies to be poor at regulating their body temperatures and lack functional brown fat tissue, which is composed of fat cells responsible for burning energy to produce heat.
To fix the mutation, the scientists—led by stem cell and reproductive biologist Jianguo Zhao of the Chinese Academy of Sciences—turned to a new gene editing tool, CRISPR/Cas9. The tool allowed the researchers to restore the UCP1 gene in embryonic pig cells using a copy of the gene from mice. The result was the birth of 12 healthy, less-porky porkers.
In subsequent tests, Zhao and colleagues found that the piglets were better at regulating their internal temperatures during a four-hour cold test. Their ratio of lean meat to total weight increased—from about 50 percent in normal pigs to about 53 percent in the engineered piglets. And the ratio of fat to total weight decreased by about 24 percent—from 20 percent in normal pigs to about 15 percent in the engineered piglets.
The study needs to be repeated with more animals to confirm the results and test the health—and taste—of the animals. And even if the findings hold, it’s unclear if the pigs would ever be allowed for food use in the US. The Food and Drug Administration has allowed genetically modified salmon, but that took decades.
But Zhao and his colleagues are optimistic that these sows will be sizzling in the future:
The development of this pig model is not only valuable for the alleviation of a major economic and welfare issue but also leads to the improvement of economically important pig meat traits.