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New paper in which we built synthetic gene regulatory networks to control pneumococcal virulence in vivo. This project started in 2009 (!) so very happy to now see it out in @PNASNews. A short thread 1/12 https://www.pnas.org/content/early/2020/10/20/1920015117
When Robin Sorg joined my lab as a PhD student in 2009, at that time @univgroningen, we were very much inspired by the then up-and-coming field of synthetic biology. You know the 'what I cannot create you cannot understand' rhetoric. 2/12
So we thought we needed to be able to build synthetic gene regulatory networks in the major opportunistic human pathogen Streptococcus pneumoniae (our favorite bacterium) to be able to understand how it becomes virulent. 3/12
The problem was, at that time, we didn't even have good inducible promoters to work with. So Robin created a one-in-all selection/counterselection system to obtain a small library of synthetic promoters of variable strengths. 4/12
Using this library, we were able to functionalize E. coli TetR and LacI and create tight inducible promoters that show expression ranges of four orders of magnitude. Having this knowledge, allowed us to build more complex gene regulatory networks. 5/12
Various logic gates were made as well as toggle switches in which cells are either in the 'ON' state or in the 'OFF' state. Robin then graduated and moved on to do very exciting synthetic biology @Genencor. We moved countries to join @unil @DMF_UNIL. 6/12
Fortunately, @ClementGallay stepped in and showed that these toggle switches work as advertised in vitro. See below one of his movies demonstrating pneumococci randomly switching to either the 'ON' or 'OFF' state. 7/12
This was all great, and the systems were being used by my lab and many other labs very successfully, but we still were not much closer at controlling virulence. Using the now available toolbox, Clement rewired control of the capsule, the main pneumococcal virulence factor. 8/12
Because of a long standing collaboration with the team of @JCSirard @PasteurLille (look out for another cool paper coming out soon!), we were now even able to test whether these newly YES (ON with inducer) and IMPLY (ON wo inducer) networks would work in vivo. 9/12
Using an influenza A virus superinfection murine model of pneumonia, we could show that the networks can control the level of virulence. Induction of TetR in pneumo could be efficiently reached by using doxycycline-containing mouse food. 10/12
This was a long project with several achievements: -generation of a set of inducible promoters and synthetic GRNs in pneumo. -one of the first single copy toggle switches. -one of the first studies (perhaps the first?) in which a synthetic GRN controls virulence in vivo. 11/12
This work now opens up the field of using synthetic GRNs to test several outstanding questions in infection biology. It also shows that innovative science takes time and long term financial support. For that I'm grateful to @univgroningen @unil @snsf_ch @ERC_Research 12/12
