Security device

From 2007.igem.org

(Difference between revisions)
Line 8: Line 8:
* EVENT 1  
* EVENT 1  
-
In order to achieve massive induction of recombination,, we could add inducible promoter in regulation of Cre expression (pBad for example). It could allow us to differentiate every cell into somatic cell. The generation of a substantial number of somatic cells should be possible if we let the system work alone (positive feedback by pDAPA). And once this number is enough we could add arabinose to express Cre in every germ cell (long and strong induction), leading to massive G to S differentiation.  
+
In order to achieve massive induction of recombination, a dormant copy of Cre site specific recombinase could be added to the SMB system. This copy would be plasmid born & would placed under control of an inducible promoter.
-
But a certain proportion of G cells would however persist.
+
But a certain proportion of G cells would most certainly persist undifferentiated.
* EVENT 2
* EVENT 2
-
The solution to second challenge could be coupling the high recombination switch to a retarded suicide switch in the gem line cells. This could be the expression of ccdB suicide gene in the germ line cells.
+
The solution to second challenge could be coupling the high recombination switch to a delayed suicide switch in the gem line cells. include the expression of ccdB suicide gene in the germ line cells.
-
This could be the opportunity to practically apply one of the founder principles of synthetic biology: modularity in systems assembly.
+
This could be the opportunity to practically apply one of the founding principles of synthetic biology: modularity in systems assembly & organisation.
Indeed, a time delay circuit has already been described, constructed & theoretically studied (Sara Hooshangi et al. 2005, Sara Hooshangi et al. 2006 and Juan M. Pedraza et al. 2006).
Indeed, a time delay circuit has already been described, constructed & theoretically studied (Sara Hooshangi et al. 2005, Sara Hooshangi et al. 2006 and Juan M. Pedraza et al. 2006).
Using such a time delay circuit could allow using a single signal to induce event 1, followed after a delay by event 2.
Using such a time delay circuit could allow using a single signal to induce event 1, followed after a delay by event 2.
Line 22: Line 22:
In addition
In addition
-
Size based screening could be perfomed before envoronmental release. Indeed, S cells having lost FtsK expression present an interresting phenotype: they grow in size without division taking place. The size threshold used in the cell sorting process should be determined by studying size distribution within germ cell and somatic cell populations. This could to improve security. <br>
+
Size based screening could be performed before environmental release. Indeed, S cells having lost ftsK expression present an interesting phenotype: they grow in size without division taking place, they "filament". The size threshold used in the cell sorting process should be determined by studying size distribution within germ cell and somatic cell populations. This could to improve security. <br>
Line 28: Line 28:
-
 
+
In the figure above, the recombination procress accompanying differentiation would lead to the transcription of a ccdB lock in somatic cells. This should protect the somatic cells from the suicide event that germ line cells go through. This lock could be a post transcriptional regulatory mechanism as this class of regulation requires less  latency time before appearing. 

Revision as of 20:51, 26 October 2007

Back to Paris/Applications


As indicated earlier, in order for the modified SMB to behave as a secure source of sterile somatic cells, two events should be initiated upon activation of a switch. This could be done in the following manner:

Security scheme.jpg
  • EVENT 1

In order to achieve massive induction of recombination, a dormant copy of Cre site specific recombinase could be added to the SMB system. This copy would be plasmid born & would placed under control of an inducible promoter. But a certain proportion of G cells would most certainly persist undifferentiated.

  • EVENT 2

The solution to second challenge could be coupling the high recombination switch to a delayed suicide switch in the gem line cells. include the expression of ccdB suicide gene in the germ line cells.

This could be the opportunity to practically apply one of the founding principles of synthetic biology: modularity in systems assembly & organisation. Indeed, a time delay circuit has already been described, constructed & theoretically studied (Sara Hooshangi et al. 2005, Sara Hooshangi et al. 2006 and Juan M. Pedraza et al. 2006). Using such a time delay circuit could allow using a single signal to induce event 1, followed after a delay by event 2.


In addition Size based screening could be performed before environmental release. Indeed, S cells having lost ftsK expression present an interesting phenotype: they grow in size without division taking place, they "filament". The size threshold used in the cell sorting process should be determined by studying size distribution within germ cell and somatic cell populations. This could to improve security.


Security device.jpg


In the figure above, the recombination procress accompanying differentiation would lead to the transcription of a ccdB lock in somatic cells. This should protect the somatic cells from the suicide event that germ line cells go through. This lock could be a post transcriptional regulatory mechanism as this class of regulation requires less latency time before appearing.


References

  • Ultrasensitivity and noise propagation in a synthetic transcriptional cascade

Sara Hooshangi, Stephan Thiberge, and Ron Weiss PNAS March 8, 2005 vol.102 no. 10 p3581–3586

  • Noise Propagation in Gene Networks

Juan M. Pedraza and Alexander van Oudenaarden SCIENCE March 25, 2005 vol.307

  • The effect of negative feedback on noise propagation in transcriptional gene networks

Sara Hooshangi and Ron Weiss CHAOS 16, 026108 (2006)