Synthetic biology involves designing artificial DNA parts called gene circuits. These circuits go into cells to change their function, like turning stem cells into neurons or making proteins to fight diseases such as fragile X syndrome, a genetic condition that affects learning and behavior. Scientists often use safe viruses to carry these circuits into cells. The challenge has been getting all cells to produce the right amount of the target protein, since some cells absorb more circuit copies than others, and cells naturally vary in their output.
Engineers at MIT created a system called DIAL to fix this. It sets a specific protein level, or "set point," for the gene circuit. This set point can be adjusted even after delivery. The system works by controlling the space between the promoter - a DNA section where control proteins bind to start gene activity - and the gene itself. A longer spacer reduces expression by making it harder for those proteins to activate the gene. To raise expression, an enzyme named Cre recombinase cuts out spacer sections, pulling the promoter closer. This research is published in Nature Biotechnology.
Dialing up gene expression
This setup lets researchers pick levels like high, medium, low, or off. They tested it in mouse and human cells, delivering genes for glowing proteins or working ones, and got even output across all cells. Uniform control matters because uneven levels have slowed reliable synthetic biology tools. Natural cell differences and extra variables make stable systems hard to build.
In one test, the system delivered varying amounts of a gene called HRasG12V to mouse skin cells, or fibroblasts. This gene speeds up their change into neurons. Higher doses led to more successful conversions. Now, scientists can study how different amounts of transcription factors - proteins that guide gene switches - affect cell changes and what types result.
The DIAL system pairs well with another tool, ComMAND, which uses a feedback loop to avoid excess protein. Together, they could customize therapies for patients, ensuring steady protein levels in specific cells. This modularity means it fits many genes and cell types, opening doors to personalized treatments.