Scientists in Japan have created genetically modified mice whose sperm glows, allowing researchers to watch male fertility inside the body in real time without surgery or killing the animal.
According to a report from Japan Science and Technology Agency, the breakthrough was developed by an international research team spanning Hokkaido University, Osaka University, and Queen’s University Belfast, and was published in the journal MedComm on January 4, 2026.
The new mice were genetically engineered, so their sperm cells emit light, letting scientists track fertility inside the body in real time. Using a special imaging camera, researchers can see how fertility is damaged or recovers over time in the same living animal.
Scientists have created mice with glowing sperm
Until now, testing whether drugs, radiation, or chemicals damage male fertility meant breeding animals and then dissecting them to study their organs. The JST says this breakthrough replaces much of that process with continuous, non-invasive monitoring, dramatically speeding up testing while producing more precise data.
The technology is expected to be used in drug development, environmental chemical safety, and cancer treatment research, where radiation and chemotherapy can severely impact male fertility. It also supports the global push to reduce animal testing, since fewer mice are needed when the same individual can be monitored over long periods.
It’s certainly one of science’s stranger research projects, but it’s hoped that it will lead to a serious breakthrough. So, thanks to some little rodents with their special glow-in-the-dark powers, the future of male fertility research is looking bright.
