Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome
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Creation of a Bacterial Cell Controlledby a Chemically Synthesized Genome
Dan Gibson, +21, Ham Smith and Craig Venter
Science (2010) 329: 52
New Directions: The Ethics of Synthetic Biology and Emerging Technologies
December 2010
20.020(S11) 02.09.11
Presidential Commissionfor the Study of Bioethical Issues
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Summary
• Synthesis and transplantation of M. mycoides genome into closely related species, M. capricolum– Rationally designed some DNA elements– Tools used to generate transplanted DNA include
chemical DNA synthesis, cloning in E. coli, recombination in S. cerevisiae
– Tools used to transplant into recipient cell include in vitro processing of DNA, agar plug purification of large DNA assemblies and inactivation of host restriction system
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Background: writing DNA vs reading DNA
Productivity measured in bp of oligos/person/day
Cost measured in $/bp of genes
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Background: reading DNA vs writing DNA
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Goal: build a working cell that uses a synthetic genome
• Design, synthesis and assembly of largest functional genome to date
art from Drew Endy
aka “Darwin is dead”
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Goal: build a working cell that uses a synthetic genome
• Design, synthesis and assembly of largest functional genome to date
aka “Darwin is dead”
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Goal: build a working cell that uses a synthetic genome
• Design, synthesis and assembly of largest functional genome to date
“JCVI-syn1.0”
Previous successes* Gibson et al. Science 2008
Complete Chemical Synthesis, Assembly, and Cloning of a Mycoplasma genitalium Genome ( ~600, 000 bp in yeast)
* Lartigue et al. Science 2007Genome Transplantation in Bacteria: Changing One Species to
Another
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Approach
• Writing DNA
Itaya Nature Biotechnology : (2010) 28: 687–689
2 polished M. mycoides genomesCP001621 CP001668 (aka YCpMmyc1.1)
4 “watermark” sequences
Also wrote in TetR and LacZ
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Approach
• Writing DNA• Assembling DNA
Itaya Nature Biotechnology : (2010) 28: 687–689
Chemical synthesis of ~1kb sequences
Cloning + recombination for
10, 100 kb and 1Mb fragments
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Approach
• Writing DNA• Assembling DNA• Transplanting DNA to M. capricolum
Itaya Nature Biotechnology : (2010) 28: 687–689
In vitro methylation and deprotonation
inactivated restriction enzyme gene (MCAP0050)
Agarose plug isolation of DNA
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Technical Achievement (1): Assembly
Figure 1Science (2010) 329: 52
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Technical Achievement (1): Assembly
Figure 2 Science (2010) 329: 52
Method: mixed 10X 1080 bp cassettes 10 kb 80-bp overlaps to adjacent cassettes
Recombined in S. cerevisiae~10 candidates transferred to E. coli
Success rate varied (10-100%)
19/111 assemblies were corrected for sequence errors
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Technical Achievement (1): Assembly
Figure 2 Science (2010) 329: 52
Method 10X 10 kb assemblies 100 kb, with 10 specific primer pairs
Muliplex PCR Recombined in S. cerevisiaeUnstable in E. coli
Success rate usually 25%
Incorrect instances include partial deletions and duplications
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Technical Achievement (1): Assembly
Figure 2 Science (2010) 329: 52
Method: 100 kb assemblies 1.08 Mb Spheroplast S. cerevisiae (~1ug DNA/400 ml cells)
Separate circular from linear, release 100 kb insert from circular, pool and co-transform, check assembly junctions
1/48 “sMmYCp235”produced all 11 amplicons seen in WT genome (Fig. 3A)
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Technical Achievement (2): Transplantation
http://www.nytimes.com/imagepages/2007/06/29/science/20070629CELL_GRAPHIC.html
Lartigue (2007)
Modify recipient restriction system
Scored for TetR and blue on X-gal
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Technical Achievement (2): Transplantation
1.0
WT
Figure 4 and 5 Science (2010) 329: 52
PCR for watermarksDigests of genome plugs
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Conclusions
• According to JCVI:“The synthetic cell is called Mycoplasma
mycoides JCVI-syn1.0 and is the proof of principle that genomes can be designed in the computer, chemically made in the laboratory and transplanted into a recipient cell to produce a new self-replicating cell controlled only by the synthetic genome.”
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Conclusions
• According to Venter on CNN:“We built it from four bottles of chemicals.”“So it's the first living self-replicating cell that we
have on the planet whose DNA was made chemically and designed in the computer.”
“So it has no genetic ancestors. Its parent is a computer.”
http://www.cnn.com/2010/HEALTH/05/21/venter.qa/index.html
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Conclusions
• According to Jim Collins (BU):“This is an important advance in our ability to
re-engineer organisms, not make new life from scratch…Although some of us in synthetic biology have delusions of grandeur, our goals are much more modest."
http://www.nature.com/news/2010/100520/full/news.2010.255.html
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Perspectives
• “Build a cell”(1) mycoides and capricolum nearly identical(2) “synthetic genome” is knock-off
• Cost ($ and time)
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5 ethical principles
Relevant to considering the social implications of emerging technologies:
(1) public beneficence(2) responsible stewardship(3) intellectual freedom and responsibility (4) democratic deliberation(5) justice and fairness
Intended to illuminate and guide public policy choices
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18 recommendations
Public beneficence: maximize public benefits and minimize public harm
(1) Public Funding Review and Disclosure(2) Support for Promising Research(3) Innovation Through Sharing
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18 recommendations
Responsible stewardship: concern for those who are not in a position to represent themselves, and for the environment
(4) Coordinated Approach to Synthetic Biology(5) Risk Assessment Review and Field Release Gap Analysis(6) Monitoring, Containment, and Control(7) Risk Assessment Prior to Field Release(8) International Coordination and Dialogue(9) Ethics Education(10) Ongoing Evaluation of Objections
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18 recommendations
Intellectual freedom and responsibility: use creative potential in morally accountable ways
(11) Fostering Responsibility and Accountability(12) Periodic Assessment of Security and Safety Risks(13) Oversight Controls
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18 recommendations
Democratic deliberation: collaborative decision making that embraces respectful debate of opposing views and active participation by citizens
(14) Scientific, Religious, and Civic Engagement(15) Information Accuracy(16) Public Education
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18 recommendations
Justice and fairness: distribution of benefits and burdens across society
(17) Risks in Research(18) Risks and Benefits in Commercial Production and Distribution
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