Almost all living organisms possess internal biological clocks that oversee periods of sleep and wakefulness and ensure that these processes synchronize with the external environment. Now, researchers from the Max Planck Society have discovered that mice with deviant internal biological clocks stimulated by a genetic mutation have less offspring and shorter lifespans than mice whose internal rhythms follow the 24-hour day cycle accurately. This points to internal clocks as essential for not only coordinating the processes of life but also maintaining biological fitness.
The scientists utilized a mutation called tau, which is known to alter daily rhythms, and examined the effects of this mutation on biological fitness. Mice with this mutation possess deviant circadian rhythms and were observed in large outdoor enclosures for more than one year while being exposed to natural predators. Each group lived with an equal amount of mice without the mutation.
The results showed that mice without the tau mutation lived longer and produced more offspring than mice with the mutation that stimulated abnormal biological rhythms. This is evidenced in the fact that after more than one year in the housing, the prevalence of the tau gene dropped from 50 percent to 20 percent, leading the researchers to believe that there are strong natural selection pressures against the tau mutation.
"Our findings highlight the fundamental importance of circadian clocks for the biological fitness of living beings. This has never been shown that clearly," said Michaela Hau, senior author of the study, in a press release.
The findings were published in the Dec. 7 issue of the Proceedings of the National Academy of Sciences.
