Researchers have created a biological switch that turns protein expression on at will using a cheap, non-toxic amino acid as the control, according to a paper published today in Scientific Reports. The switch enables control of genome editing tools that may be used to regulate desired genetic changes through entire populations for industries such as biomedicine or agriculture.
Unlike other switches, the method does not use antibiotics, which can select for bacterial antibiotic resistance, and it does not run the risk of being expressed in ‘off’ mode, such as in switches that rely on temperature or light. It relies instead on an amino acid called BOC, which is similar to lysine. BOC is cheap, plentiful, non-toxic, and environmentally-friendly according to the University of Bath and Cardiff University scientists.
The method was tested in transgenic mice carrying a gene that makes their skin glow green in UV light. The researchers included something called a ‘genetic code expansion toolkit’ in the mouse genomes at birth. The toolkit, which in this case turned off the green glow when turned on, was programmed to only work in the presence of BOC. The researchers were able to achieve BOC-dependent activation in the mouse embryos as well as cultured cells.
The researchers see many potential research and practical applications for this technology. For example, it could be used to investigate processes like aging in cells, offer a new tier of control in gene therapy, or in gene drive technology. Gene drive technology can use CRISPR-Cas9 editing to ensure all offspring in a sexually reproducing species inherit a particular genetic segment. Such characteristics can be used, for example, to make all female mosquitos infertile to control malaria spread, but proof of safety must be proven before such drives can be undertaken. The researchers believe BOC switches can help in such efforts.
"What sets our work apart is the potential for this as an environmentally friendly switch across large distances, which no previous method really enables. For example you can imagine controlling gene drive activity in livestock herds by adding or removing BOC from feedstuffs as required,” said Professor Tony Perry, who led the Bath team from the Department of Biology & Biochemistry. The researchers plan to continue their studies to further validate and refine their results.
Image: The left-side group of mice is a control—with neither the gene editing RNA, nor the BOC switch. The next group has BOC but no RNA, and the third has the RNA, but no BOC to switch it on. The final group on the right has the gene editing machinery and the BOC switch. BOC activates the switch and the pups are born without green fluorescence. Image courtesy of Tony Perry/University of Bath.