Download Document

Ethical Issues of Genomes,
Genetics, and Genetic Engineering
1
Examples of Questions that can now
be raised as a result of HGP
• Genetic testing, health insurance, and privacy
– heart attack gene recently found in Iowa family (would you want
this known?, would your descendents?)
– Genetic marker for IQ (Gattaca)
– Deafness -- may be increase in IQ
• Genetic engineering
• Cloning and therapeutic cloning
– primates, pigs, fish?
• Basic research in virulent or infectious organisms (anthrax)
• Stem cell research
– Economic and moral issues
– Offshore?
2
Genetic Engineering
• Definition: alteration of genetic code by “artificial means”
– Examples? (within the system?):
• dog breeds
• corn selectively bred for 1000’s of years
– More “artificial”
• goats with spider gene to create spider silk in milk
• GFP (green fluorescent protein – jellyfish) into many different
organisms (trypanosomes, zebrafish) and luciferase
– More practically, in medicine (gene therapy)
• introduction of a normal copy of a gene for a diseased, missing, or
non-functional gene
• insulin
3
Gene Therapy Challenges
• Have to know and understand the cause
– “You cannot fix something unless you know it is
broken.”
• Safety and unexpected consequences
• Delivery method.
– How do you get a “good” copy of a gene to replace a
“bad” copy of a gene in all tissues of an organ?
– Engineering challenge
4
Genetic Engineering
• Ethical and legal issues
– is it appropriate to splice “unnatural” genes into
organisms?
• Concern is that this could lead to a catastrophe
–
–
–
–
"environmental" damage?
"un-natural" organisms (infectious organism)
good news is that it has not happened yet
bad news is that an absence of evidence is not evidence
of absence.
– lateral gene transfer: the transfer of genes between
organisms
– there is evidence that suggests gene transfer has
occurred between organisms (mitochondria in humans) 5
Case Study: Genetic Engineering
(Gene Therapy)
• Cavazzana-Calvo M, Hacein-Bey S, de
Saint Basile G, Gross F, Yvon E, Nusbaum
P, Selz F, Hue C, Certain S, Casanova JL,
Bousso P, Deist FL, Fischer A., “Gene
therapy of human severe combined
immunodeficiency (SCID)-X1 disease.”
Science. 2000 Apr 28;288(5466):669-72.
6
SCID-X1 - Overview
• severe combined immunodeficiency X1
(SCIDX1, aka IL2RG) www.ensembl.org
• X-linked inherited disorder
• OMIM – disease information
– www.ncbi.nih.gov/entrez/query.fcgi?db=OMIM
• recessive disorder
– consequences for males VS females
7
Male VS Female
SCIDX1
SCIDX1
X Y
X X
8
SCID-X1
• 1-2 in 100,000 (30-40% of all SCID in US)
medicine.ucsd.edu/peds/Pediatric%20Links/Links/AllergyImmunology/T%20Cell%20Immunodefici
encies%20Ped%20Clin%20of%20NA%20Dec%202000.htm
• characterized by block in early T and “natural
killer” (NK) lymphocyte cell differentiation
• caused by mutations in “gama-C” gene, aka
SCIDX1
• usually fatal in first year of life
• severe infections (no immune response)
• The Boy in the Plastic Bubble
9
SCIDX1
• bone marrow transplant can be successful,
but requires compatible donor (applies to
less than 1/3 of cases)
10
SCIDX1 Gene Therapy
• retro virus (modified murine/mouse RNA
virus) as vector
– delivery method
– alternative delivery methods???
• implantation of devices
11
Modify the
virus so
that it
infects, but
does not
replicate.
http://www.accessexcellence.org/AB/GG/retrovirus.gif
12
SCIDX1 Therapy
• Anticipated that transformed lymphoid progenitor
cells will have selective advantage
– transmits “survival” and “proliferative” signals to
progenitor cells
• known that wild-type retroviruses can contribute
to cancerous changes if insertion perturbs a gene –
“insertional oncogenesis”
• accepted as unlikely but possible risk
13
SCIDX1 Therapy
• Initial study – 2 boys in France
– removed bone marrow
– modified vector
• inserted gama-C gene
• disabled reproductive capability of virus
– “infected” bone marrow “ex-vivo”
– virus inserts into genome carrying therapeutic gene
– re-implanted infected bone marrow (and all progeny
cells) which should supplant the defective cells
14
SCIDX1 Therapy
• 747 analogy
– human body is complex system, components,
networks, control, regulation, feedback, etc.
– know a component is non-functional, but have
incomplete understanding of relationship to the
rest of the system
15
Results
• April 2000
–
–
–
–
–
–
skin lesions disappeared
both left protective isolation after 95 days
at home for 10 and 11 months
normal growth and motor development
no side effects
study expanded to 3rd recipient, with similar
results
16
Results (Part 2)
• Sustained correction of X-linked severe combined
immunodeficiency by ex vivo gene therapy -- NEJM
• April 18th, 2002
– 2.5 years
– no adverse results
– “Ex vivo gene therapy with gamma(c) can safely correct the
immune deficiency of patients with X-linked severe combined
immunodeficiency.”
•
•
•
•
This is outstanding!!!
Paving the way for other disorders
Multiple studies underway, including US
$250 M per year on genome (US) well spent
17
Gene Therapy
Challenges Revisited
• Have to know and understand the cause
– SCIDX gene defective
• Safety and unexpected consequences
– “Appears to be okay*.”
• Delivery method.
– How do you get a “good” copy of a gene to replace a “bad” copy
of a gene in all tissues of an organ?
– Engineering challenge
– Answer: borrow an existing mechanism from nature -- the
retrovirus
18
Results (Part 3)
• 3 years
• 10/11 successfully treated
• October, 2002
– “French gene therapy group reports on the adverse
event in a clinical trial of gene therapy for X-linked
severe combined immune deficiency (X-SCID)” –
Journal of Gene Medicine
– 30 months after treatment
– leukemia
– chemotherapy
– history of leukemia in family
19
Results (Part 4)
• January 14, 2003
– Report of a second serious adverse event in a clinical
trail of gene therapy for X-linked severe combined
immune deficiency (X-SCID) – Journal of Gene
Medicine
– 3 year-old (2 years, 9 months after treatment)
– leukemia (no history)
– chemo
– study halted
• 30 studies in US halted by FDA
• 3 years better than nothing? (what percentage?)
20
What Happened?
• Mapping integration site
– appears to have integrated near LMO-2 gene in both
individuals (in tumors)
– still under review
• Other groups have shown that the AIDS virus
tends to insert in genes that are actively expressed
– theory -- DNA has to be unpackaged to express genes,
and viruses may rely on this mechanism for integration
21
Take Home Messages
• Recent advances in science is forcing policy
makers to try and make difficult decisions
– Genetic engineering
– Cloning
– Stem cell research
• Important to understand the basics of the science
in making these decisions
• Many of the policies have yet to be determined
and may significantly influence basic science,
research, the economy, and human health
– example: stem cell research ban prior to Clinton
administration
22
Where's the Bioinformatics?
• Groups have started exploring different vectors
–
–
–
–
–
–
–
identify integration sites
know the vector sequence
may design "primers" to "amplify" vector
read resulting sequence directly
align to human genome – and "see" where it integrates
manually – may do 10, 50? 100?
800
23
Analysis Pipeline
Perl
Sequence
Read
Quality
Processing
BLAST
Sequence
Characteristics
Statistics
and Reports
Genome
Indices
Acquire Gene
Positions (Ensembl)
24
Other Efforts
25
26
Ali, Bainbridge
27
End
28
NIH RoadMap
• toolbox (small molecules)
– procedure for when interesting target or marker
is identified
– currently, academic labs don't have the
resources to pursue targets
– "open source" drug discovery
29