Recording of elapsed time and temporal information about biological events using Cas9

DNA has not been utilized to record temporal information, although DNA has been used to record biological information and to compute mathematical problems. Here, we found that indel generation by Cas9 and guide RNA can occur at steady rates, in contrast to typical dynamic biological reactions, and the accumulated indel frequency can be a function of time. By measuring indel frequencies, we developed a method for recording and measuring absolute time periods over hours to weeks in mammalian cells. These time-recordings were conducted in several cell types, with different promoters and delivery vectors for Cas9, and in both cultured cells and cells of living mice. As applications, we recorded the duration of chemical exposure and the lengths of elapsed time since the onset of biological events (e.g., heat exposure and inflammation). We propose that our systems could serve as synthetic DNA clocks.''

Automated summary

The study discovered that indel generation by Cas9 and guide RNA can be used to measure absolute time periods in mammalian cells. The method was successfully applied in various cell types and living mice to record the duration of chemical exposure and the elapsed time since the onset of biological events. The system proposed in the study could potentially serve as synthetic DNA clocks.