Security device

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Back to [[Paris/Applications]]
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As indicated earlier, in order for the modified SMB to behave as a secure source of sterile somatic cells, three events should be initiated upon activation of a switch. This could be done in the following manner:
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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:
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[[Image: security device.jpg|center|500px]]
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[[Image: security scheme.jpg|center|400px]]
* EVENT 1  
* EVENT 1  
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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.  
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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.
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But a certain proportion of G cells would however persist.
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But a certain proportion of G cells would most certainly persist undifferentiated.
* EVENT 2
* EVENT 2
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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.
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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.
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This could be the opportunity to practically apply one of the founder principles of synthetic biology: modularity in systems assembly.
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 +
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.
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* EVENT 3
 
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We could also be able to screen the somatic cells by the size. Indeed S cells that have lost FtsK expression present a strange phenotype: they grows without dividing. We also could keep big cells (Cell sorting). The threshold should be determined by studying the size repartition of germ cells and somatic cells to improve sensitivity and specificity of our test. <br>
 
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In addition
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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>
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[[Image: security scheme.jpg|center|400px]]
 
 +
[[Image: security device.jpg|center|500px]]
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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==
==References==
 +
 +
===Time delay circuit===
*'''Ultrasensitivity and noise propagation in a synthetic transcriptional cascade'''
*'''Ultrasensitivity and noise propagation in a synthetic transcriptional cascade'''
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Sara Hooshangi and Ron Weiss
Sara Hooshangi and Ron Weiss
CHAOS 16, 026108 (2006)
CHAOS 16, 026108 (2006)
 +
 +
 +
===RNA based regulation in Synthetic Biology===
 +
 +
*'''RNA synthetic biology'''.
 +
Farren J Isaacs1, Daniel J Dwyer2,3 & James J Collins3.
 +
NATURE BIOTECHNOLOGY Review VOLUME 24 NUMBER 5 MAY 2006.
 +
 +
 +
'''Engineered riboregulators'''
 +
 +
*'''Engineered riboregulators enable post-transcriptional control of'''.
 +
Isaacs, F.J. et al.
 +
gene expression. Nat. Biotechnol. 22, 841–847 (2004).
 +
 +
 +
'''Ribosome mRNA pairing'''
 +
 +
*'''network of orthogonal ribosome-mRNA pairs'''.
 +
Rackham, O. & Chin, J.W. A.
 +
Nat.Chem. Biol. 1, 159–166 (2005).
 +
 +
*'''Cellular logic with orthogonal ribosomes'''.
 +
Rackham, O. & Chin, J.W.
 +
J. Am. Chem. Soc. 127, 17584–17585 (2005).
 +
 +
 +
'''Engineered ligand-controlled riboregulators (Riboswitches)'''
 +
 +
*'''Controlling gene expression in living cells through small
 +
molecule-RNA interactions'''.
 +
Werstuck, G. & Green, M.R.
 +
Science 282, 296–298 (1998).
 +
 +
*'''theophylline responsive riboswitch based on helix slipping controls
 +
gene expression in vivo.'''.
 +
Suess, B., Fink, B., Berens, C., Stentz, R. & Hillen, W. A.
 +
Nucleic Acids Res. 32, 1610–1614 (2004).
 +
 +
*'''Programmable ligand-controlled riboregulators of eukaryotic
 +
gene expression'''.
 +
Bayer, T.S. & Smolke, C.D.
 +
Nat. Biotechnol. 23, 337–343 (2005).
 +
 +
Back to [[Paris/Applications|Perspectives]]

Latest revision as of 23:59, 26 October 2007

Back to Perspectives


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

Time delay circuit

  • 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)


RNA based regulation in Synthetic Biology

  • RNA synthetic biology.

Farren J Isaacs1, Daniel J Dwyer2,3 & James J Collins3. NATURE BIOTECHNOLOGY Review VOLUME 24 NUMBER 5 MAY 2006.


Engineered riboregulators

  • Engineered riboregulators enable post-transcriptional control of.

Isaacs, F.J. et al. gene expression. Nat. Biotechnol. 22, 841–847 (2004).


Ribosome mRNA pairing

  • network of orthogonal ribosome-mRNA pairs.

Rackham, O. & Chin, J.W. A. Nat.Chem. Biol. 1, 159–166 (2005).

  • Cellular logic with orthogonal ribosomes.

Rackham, O. & Chin, J.W. J. Am. Chem. Soc. 127, 17584–17585 (2005).


Engineered ligand-controlled riboregulators (Riboswitches)

  • Controlling gene expression in living cells through small

molecule-RNA interactions. Werstuck, G. & Green, M.R. Science 282, 296–298 (1998).

  • theophylline responsive riboswitch based on helix slipping controls

gene expression in vivo.. Suess, B., Fink, B., Berens, C., Stentz, R. & Hillen, W. A. Nucleic Acids Res. 32, 1610–1614 (2004).

  • Programmable ligand-controlled riboregulators of eukaryotic

gene expression. Bayer, T.S. & Smolke, C.D. Nat. Biotechnol. 23, 337–343 (2005).

Back to Perspectives

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