A new study on thousands of rats suggests that the genes of social partners can shape an individual's gut microbiome through shared microbes. Researchers found stronger genetic influences when accounting for these social effects. The findings highlight indirect ways genetics affect health via microbial exchange.
Published on December 18 in Nature Communications, the research examined over 4,000 genetically unique rats from four cohorts housed at different U.S. facilities. These controlled conditions allowed scientists to isolate genetic impacts on the gut microbiome, which consists of trillions of microorganisms aiding digestion and health.
The team, from the Centre for Genomic Regulation in Barcelona and the University of California San Diego, identified three genetic regions consistently linked to specific bacteria across environments. The gene St6galnac1, which modifies gut mucus with sugars, correlated with higher levels of Paraprevotella bacteria. Mucin genes, forming the gut's protective layer, associated with Firmicutes bacteria, while the Pip gene, producing antibacterial molecules, connected to Muribaculaceae family members.
By modeling indirect genetic effects—where one rat's genes influence cage mates via microbe sharing—the study revealed that social factors amplified genetic influences four to eight times for these links. "This is not magic, but rather the result of genetic influences spilling over to others through social contact. Genes shape the gut microbiome and we found that it is not just our own genes that matter," said senior author Dr. Amelie Baud.
The results suggest genes can indirectly alter others' biology without DNA transfer. In humans, similar mechanisms might underestimate genetic roles in health issues like immune function or metabolism. The rat St6galnac1 relates to human ST6GAL1, previously tied to Paraprevotella and conditions such as COVID-19 susceptibility or IgA nephropathy. Dr. Baud noted, "We've probably only uncovered the tip of the iceberg."
Future work will probe these microbe-gene interactions further, potentially clarifying health links.
