Download using the crispr/cas9 gene editing tool to develop a cure for

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USING THE CRISPR/CAS9 GENE EDITING TOOL TO DEVELOP A CURE
FOR DUCHENNE MUSCULAR DYSTROPHY
Kris Keppel, [email protected], Vidic 2:00, Brendan Lettrich, [email protected], Vidic 2:00
Abstract- CRISPR, short for Clustered Regularly Interspaced
Short Palindromic Repeats, is a revolutionary gene editing
system that has the power to cut and paste any section of DNA
and potentially cure many genetic diseases. CRISPR consists
of two parts, with its partner enzyme “cas9” performing the
cutting and pasting, and CRISPR being an RNA sequence that
guides the enzyme to the proper location in the cell. It can be
programmed to locate any gene, and can cut hundreds of
bases or just a few. While CRISPR has also been applied to
agriculture and other fields, the focus of this paper is on the
use of this technology in the search for a cure for Duchenne
muscular dystrophy (DMD), which affects one in every 3500
men. This paper will be organized into four main sections.
The first two will cover background information on CRISPR
and DMD, delving into topics such as the technicalities of
how CRISPR works, as well as past attempts to cure DMD.
The next section will investigate how CRISPR is being applied
to muscular dystrophy by looking closely at one specific
experiment which used a germline editing method to show
muscle redevelopment in mice with DMD. Finally, the last
section will cover the ethical and sustainability concerns
related to CRISPR, and this will be followed with a conclusion
that demonstrates why CRISPR is important to the conference
and to engineering.
Key Words—CRISPR/Cas9, Duchenne muscular dystrophy
(DMD), ethics, gene, muscle development, mutation, RNA
A REVOLUTION IN GENE EDITING
The field of genetic engineering has seen many
explosive discoveries over the past few decades, but few have
carried with them the potential that is harbored by a
technology known as Clustered Regularly Interspaced Short
Palindromic Repeats, better known as CRISPR. This gene
editing tool can remove any desired section of DNA, and then
insert a replacement and repair the strand just like new. It has
taken the field of genetics by storm due to its virtually
limitless potential. CRISPR’S usage in agriculture and
industry has already begun, but the focus of this paper will be
on its development as a cure for genetic diseases, specifically
Duchenne muscular dystrophy (DMD). For many of these
diseases, DMD included, the mutation that causes the disease
University of Pittsburgh, Swanson School of Engineering 1
3.3.2017
is well known, but unfortunately science has yet to discover a
mechanism by which to fix it. CRISPR has the potential to
be that mechanism, and the way in which it could do so will
be the focal point of this paper.
DUCHENNE MUSCULAR DYSTROPHY
In order to fully comprehend the significance of
applying CRISPR to find a cure for Duchenne muscular
dystrophy, some background knowledge on the disease itself
is necessary. The Muscular Dystrophy Association defines
Duchenne muscular dystrophy as “a genetic disorder
characterized by progressive muscle degeneration and
weakness” [1]. Duchenne is one of nine types of muscular
dystrophy, but it is the most common form among children.
Duchenne muscular dystrophy occurs almost exclusively in
boys, although there have been very rare cases in which it has
been documented in girls. This is because DMD is due to a
mutation in the gene that codes for the dystrophin protein,
which is located on the X chromosome. Since women carry
two X chromosomes, carriers of the disease have one proper
form of the gene and one damaged copy, but only one is
needed in order for production of dystrophin to be carried out
effectively.
In men, however, having only one X
chromosome means that if they inherit the mutated form of
the gene, they will express DMD [1].
Symptoms and Prognosis
According to the Muscular Dystrophy Association, for
children afflicted by DMD, muscle weakness typically begins
between the ages of three and five, beginning in muscles
located in the hip, thigh, and shoulder area, and later
spreading to the extremities. This will continue to progress at
a varying rate, but typically the child is forced into a
wheelchair between the ages of seven and twelve. Outside of
the physical ailment, it should be noted that DMD patients
typically have no other issues, and are both cognitively and
socially normal. However, as they progress into their teen
years, it becomes increasingly difficult to maintain a normal
life. During the teen years, the process of muscle degradation
becomes more severe in the respiratory and cardiovascular
systems, both of which tend to bring about more serious
Kris Keppel
Brendan Lettrich
problems. Respiratory complications make it difficult to
cough and thus leave patients prone to serious infection, and
heart failure is typically the ultimate cause of death in DMD
victims. Overall, the prognosis for those diagnosed with
Duchenne muscular dystrophy is an average life expectancy
of approximately twenty-five to thirty years, but recent
advances in medicine have increased longevity of life, and
there have even been some rare cases of patients living into
their forties and fifties [1].
These two findings led to the conclusion that CRISPR
actually served as an immune system of sorts within bacteria,
working with Cas9 to help protect the organism against
deadly viruses. The mechanism was simple: whenever a
previously encountered virus entered the bacteria, the
CRISPR DNA sequence that was produced from the first
encounter recognized the virus, and produced an RNA
molecule with a complementary base sequence to the viral
sequence. This molecule then paired up with a Cas9 enzyme
and lead it to the invader, where it could be destroyed.
Following this development, scientists around the world
immediately recognized the potential of this technology as a
new gene-editing device for animals and potentially humans.
Per Heidi Ledford of Nature magazine, the popularity of
CRISPR began an exponential climb, as the number of
articles published about CRISPR grew from zero in 2006 to
over 600 in 2014, and its U.S. funding jumped from
nonexistent in 2007 to over $80 million in 2014 [5].
Other Treatment Methods
While there is no cure yet developed for DMD, there
have been a few methods developed over the years that have,
at the very least, provided some relief for patients. According
to Dr. Jerry Mendell of Nationwide Children’s Hospital,
corticosteroids are the only medications that have been shown
to provide any benefit, but with them come many unpleasant
side effects. Prednisone, for example, has shown the ability
to prolong ambulation by about one or two years, but also
causes weight gain, osteoporosis, and cushingoid appearance
(swelling of the face), amongst other things [2]. Thus,
treatment with corticosteroids is not often a popular choice.
Per Dr. Chengzu Long of the University of TexasSouthwestern, aside from medication, other gene therapy
methods similar to CRISPR, such transcription activator-like
effector nucleases (TALENS) and zinc finger nucleases, have
also been attempted. These methods have shown to be
unreliable, however, because they have added a functional
copy of the gene while also retaining the mutated gene, which
leads to unreliable and often unsuccessful return of function
[3]. CRISPR, meanwhile, replaces the mutated gene with a
fully functional copy.
How CRISPR Acts as Molecular Scissors
Due to the incredibly fast rate at which the CRISPR
technology was adopted, the scientific community has
quickly improved the use of CRISPR, although there are some
variations in how it is used. The most important component
is the CRISPR RNA molecule, which includes two types of
RNA: programmable guide RNA and tracer RNA. These two
parts typically function as two separate molecules, but
Jennifer Doudna, a researcher at the University of California,
Berkeley, was able to combine these two into one complete
molecule—one that is now the most commonly used form of
CRISPR [6]. The other component is the Cas9 enzyme,
which binds to the location determined by the guide RNA, and
then performs the cutting of the target gene.
The first step in the process of removing a target gene is
to combine these two separate components into one main
complex, which can be done in one of two ways. The original,
more common way, is to simply inject both components at
once into the target animal, and allow them to form the
complex on their own. However, a new method has been
developed by Randall Platt of the Broad Institute, who
injected the Cas9 enzyme into a mouse embryo, thereby
making it a permanent part of the genome [4]. The method
by which the two are combined ultimately does not make a
difference, but Platt’s method simplifies the process and
produces many “ready-to-edit” subjects.
Once the RNA and Cas9 are combined and injected into
the cell, the complex immediately begins locating the specific
gene to bind to. This specific location is determined by the
guide RNA, a series of about twenty nucleotides, previously
programmed by scientists, which correspond to one particular
target sequence in the cell. Per Addgene, a company
specializing in the production of genetic materials, this target
sequence must meet two conditions: that it is “unique
compared to the rest of the genome,” and that “the target is
present immediately upstream from a Protospacer Adjacent
BACKGROUND INFO ON CRISPR/CAS9
CRISPR was first discovered in E. coli bacteria at the
Research Institute of Microbial Diseases in Osaka, Japan in
December of 1987 [4]. While the scientists responsible for
the discovery were able to detect these strange repeating
sequences in E. coli DNA, along with the Cas9 enzyme, they
were unable to determine their function; thus, CRISPR was
disregarded as an insignificant side note for many years. In
fact, it was not until 2005 when the next milestone was made
in the development and understanding of this technology. It
was at this time that Francisco Mojica from the University of
Alicante compared CRISPR’s DNA to that of thousands of
other organisms, and was astonished to find that each
sequence within CRISPR was in fact a fragment of DNA from
an invading virus. This was followed up in 2007 by the work
of two scientists at the Danisco food company, who found that
while many of their yogurt cultures were destroyed by
bacteria, the only ones that were saved all contained CRISPR
sequences within their genome [4].
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Brendan Lettrich
said, “In the past it was a student’s entire thesis to change one
gene, CRISPR just knocked that out of the park” [6]. This
statement displays how much CRISPR has simplified the
process of editing a gene.
Another one of CRISPR’s many advantages is the speed
at which it works, and consequently the speed at which
experiments or studies using it can be completed. In the past,
it could take scientists up to two full years to successfully
change just one gene in a population of mice. This slow pace
led to an extremely lengthy process of finding cures for
diseases, and greatly hindered the progress of the field of
genetics as a whole. With CRISPR, this has all changed. In
October 2015, researchers at Harvard University were able to
successfully alter 62 different genes simultaneously in pig
embryos with the use of CRISPR, and the whole process took
less than a year [6]. This ability provides an opportunity to
gather huge amounts of information in a relatively short
amount of time, an opportunity not presented by any other
technology.
Lastly, CRISPR is so different from other gene therapy
methods because of its low cost. Past advances in gene
editing technology, such as TALENS and zinc fingers, often
cost $5,000 or more to order [5]. Meanwhile, with CRISPR,
the total cost of the customized RNA guide strand and Cas9
together is a mere $30 [5]. This vast difference in price,
coupled with the speed, simplicity, and effectiveness of
CRISPR makes it the obvious choice for scientists involved
in genetic engineering.
Motif (PAM)” [7]. This PAM sequence is a series of only a
few bases that is vital to the cutting process, as it serves as an
activator for the Cas9 enzyme, directing the bonding between
it and the gene and initiating the cutting of the desired
sequence.
FIGURE 1 [8]
CRISPR/Cas9 complex bound to specified location in
gene
The whole complex of the Cas9 enzyme, guide RNA,
tracer RNA, and PAM sequence can be seen in Figure 1 above
from Tamar Laboratory Supplies. According to Ledford,
after the CRISPR/Cas9 complex finds the correct location
with a proper PAM sequence, it binds to the location and
“unzips” the DNA strand, so that the guide RNA sequence
can bond with its corresponding base pairs. As long as there
is sufficient homology between the RNA and DNA
sequences, the Cas9 enzyme will begin cutting and removing
the desired gene from the DNA sequence [7].
HOW CRISPR/CAS9 CAN CURE DMD
With the general idea of how CRISPR acts as a gene
cleaving tool, this knowledge can now be applied specifically
to the gene that causes Duchenne muscular dystrophy. This
investigation will delve deeper into the technical details and
experimental techniques involved in working with CRISPR
and DMD, and provide insight into how research experiments
being conducted today might ultimately lead to a cure in the
future.
WHY CRISPR IS THE PREFERRED TOOL
There have been many genetic engineering tools
discovered over the past few decades, many of which have
worked using a similar mechanism to that used by CRISPR.
Thus, it is fair to ask the question, what makes CRISPR/Cas9
so special, and why is it the overwhelmingly preferred method
among scientists today? The answer is that CRISPR is faster,
simpler, and cheaper to use than other previously discovered
technologies.
One of the main reasons CRISPR is preferred is its
simplicity in comparison to other tools. Essentially all that is
required is for one to acquire the necessary components, most
of which can be purchased very easily, and then inject them
together into the target animal. While there would clearly
need to be much planning put into the design of the
experiment, once inserted into the subject, the technology
does the rest. The best way to express just how simple this
process can be, however, is through the opinions of the
researchers themselves. In one article published by the New
York Times Magazine, author Jennifer Kahn did just that,
asking scientists working with CRISPR about the simplicity
of the technology. Bruce Conklin of the Gladstone Institutes
Mechanism by Which CRISPR Repairs the Damaged
Dystrophin Gene
Dr. Chengzu Long from the University of TexasSouthwestern became one of the first to pioneer the use of
CRISPR on DMD when he injected the system into mice
affected with the disease, and then measured the
consequential levels of muscle development. While there
have been many other similar experiments completed,
approximately the same methodology is used in each, and
thus the focus in this section will be directed only at Long’s
work.
The objective was to use the CRISPR/Cas9 system to fix
the point mutation located in exon 23 of the dystrophin gene
in mice, which causes Duchenne muscular dystrophy, and
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Brendan Lettrich
then measure how effective the procedure was in stimulating
muscle generation in the mice [3]. Long further states in his
report that the exact mutation is the misplacement of a T
nucleotide where a C nucleotide is supposed to be, which
consequently causes a premature stop codon that halts
expression of the dystrophin gene as a whole. The mutation
can be seen in greater detail in Figure 2 below.
zygotes, the zygotes were reimplanted into surrogate mothers,
who produced the offspring that Long desired. The entire
germline editing process can be summarized in Figure 3
below.
FIGURE 3 [3]
Summary of the germline technique used to produce
desired offspring
FIGURE 2 [3]
Diagram of the point mutation in exon 23 that creates
stop codon
Once in the zygote, the CRISPR/Cas9 complex acted
exactly as described earlier. The guide RNA lead the system
to the proper location, where the cas9 enzyme recognized the
PAM and bonds, and then began the cutting process. After it
has cut the DNA and removed the faulty base, either through
NHEJ or HDR, the DNA is repaired and the proper C base is
put into place [3].
The first step in the procedure was to produce a
population of mice with Duchenne muscular dystrophy. To
do so, Long used the germline technique, whereby he crossed
a female with two copies of the mutated DMD gene with a
male housing the mutated DMD gene on its only X
chromosome, thus ensuring that the parents would produce
offspring with DMD. He did not allow these two parents to
directly produce offspring, however, but rather gathered
sperm and eggs from the pair before combining them to
artificially form zygotes, which he labeled “mdx”. This
technique allowed Long to produce many offspring, while
also ensuring that each had the desired characteristic.
Additionally, Long prepared zygotes of wild-type mice,
which did not contain the mutated gene. This population of
wild-type mice served as the control group in the experiment.
After the zygotes were prepared, the next objective was
to inject the proper materials into each zygote. For this
experiment, the required materials were the guide RNA
molecule, the cas9 enzyme, and in some cases a template
RNA strand for homology-directed repair (HDR).
Homology-directed repair is a more accurate way of “sewing”
the DNA back together after it has been cleaved, as opposed
to its counterpart, nonhomologous end-joining (NHEJ),
which can at times lead to more mutations when repairing the
cut DNA. In this experiment, Long chose to use both
methods, and the results of the experiment later showed no
significant difference in muscle regeneration between the two
techniques. With the proper materials gathered, Long
injected these materials into only certain zygotes for the
purpose of creating four distinct groups of mice. The four
groups were: wild-type mice, wild-type mice with
CRISPR/Cas9, mdx mice, and mdx mice with CRISPR/Cas9.
After the CRISPR/Cas9 system was injected into the desired
Results of the Experiment
Upon completion of the experiment, the team compared
the various groups of mice based on many aspects of muscle
strength and development. Specifically, the scientists
performed histological analysis when the mice were between
seven and nine weeks old on four different types of dystrophic
muscle: quadriceps, soleus (hindlimb muscle), diaphragm
(respiratory), and heart. Notably, as a subpart of the
histological
analysis,
the
scientists
performed
immunostaining on these areas of muscle in each of the four
groups of mice, which essentially made the dystrophin protein
fluoresce so that levels of the protein could be easily
observed. Long compared pictures of each of the four muscle
groups from a wild-type mouse, an mdx mouse, two HDRrepaired mice with 17% and 41% gene correction,
respectively, and an NHEJ-repaired mouse with 83% gene
correction. As expected, the wild-type mouse showed full
dystrophin expression in each of the four areas, and the mdx
mouse displayed virtually no dystrophin expression in each of
the areas [3].
The important finding, though, was that in all three cases
in which an mdx mouse had been injected with the
CRISPR/Cas9 system, there was substantial muscle
development, to the point that, in the cases of the HDR 41%
and NHEJ 83% samples, dystrophin expression was
essentially even with that of the wild-type mouse.
Furthermore, even the other HDR sample with just 17% gene
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Brendan Lettrich
correction showed muscle regeneration that far outweighed
the level of correction at the molecular level [3]. The findings
are summarized in Figure 4 below.
arise when this is attempted on fully developed cells. There
is hope, however, as recent studies involving the adenoassociated virus (AAV) transport system have been shown to
be effective in delivering materials to somatic cells, and more
importantly have been shown to be most effective in regions
severely affected by DMD, such as skeletal and heart muscle
[3]. In fact, in a recent experiment performed by Dr.
Christopher Nelson at Duke University, the AAV system was
used to successfully deliver CRISPR/Cas9 into adult mice
suffering from DMD, and the results showed noticeable
muscle regeneration within the mice [9]. This was another
huge milestone along the path to a cure for humans.
Another problem still exists, though, in that even if
CRISPR can be safely transported into somatic cells, it will
still be very difficult to alter enough cells in order to make a
difference overall. With trillions of cells in the body, altering
the gene in just a couple hundred or even thousand will not
provide any real benefit to DMD patients. However, this is
where the satellite cells discussed earlier will come into play.
If scientists are able to direct the CRISPR/Cas9 system to the
satellite cells only, this could lead to progressive muscle
regeneration in all areas of the body, which could in turn
reverse the effects of Duchenne muscular dystrophy.
Although this is a real possibility, with all of the issues stated
above, this idealistic goal is still at least a few years away
from coming to fruition. Additionally, these are just the
scientific issues, which will not be the only obstacle standing
in the way of CRISPR.
FIGURE 4 [3]
Comparison of immunostaining of the dystrophin
protein in four different muscle types for each group of
mice
This last result was arguably the most significant finding
made by Long and his team. With just 17% gene correction
yielding up to 60% of muscle growth, clearly there must be
some way in which partial muscle development contributes to
an even greater level of regeneration. Long’s proposal for this
involved satellite cells, which are the skeletal system’s supply
of stem cells. He hypothesized that even when a small
percentage of cells contain the corrected dystrophin gene, if
some of these are satellite cells, then these can stimulate
growth in other muscle cells around them, causing
progressive regeneration of the dystrophic muscle overall [3].
It should be noted that, as a side experiment of sorts,
Long and his team also recorded the number of off-target
mutations produced by the CRISPR/Cas9 system while it was
repairing the dystrophin gene. After analyzing the data, it was
deemed that there was no higher frequency of off-target
mutations in the CRISPR modified mice when compared to
control group wild-type and mdx mice. This finding was also
quite notable, as one of the most common fears of the use of
CRISPR is that it is, at times, dangerously inaccurate [3].
SUSTAINABILITY OF CRISPR
When dealing with any emerging technology, concern must
be directed not only at its current progression, but also at its
future development, to ensure that it exhibits all the qualities
of a sustainable product. To be considered sustainable a
technology must check many boxes, but in general, according
to the UN’s 1987 Brundtland Report, sustainability can be
defined as “satisfying the needs of the present generation
without compromising the ability of future generations to
meet their own needs” [10].
Placing the focus specifically on CRISPR, however, this
definition can be whittled down to a more explicit goal:
ensuring the continued health of humans and the surrounding
environment. Many uses of genetic engineering in the field
of agriculture have generated controversy over the effects that
genetically-modified products might have on the
environment, as at times scientists are essentially creating
new species through all the genetic modifications [11]. While
there is a small chance that the use of CRISPR could have
similar negative effects, it is unlikely that such targeted and
small-scale genomic changes will have any ecological
consequences. Another common environmental concern with
technologies in just about any field of engineering is the waste
products associated with the process. Again, CRISPR poses
no issue when it comes to this. The components of CRISPR
Future Testing with CRIPSR/Cas9 and DMD
While Long’s experiment was a great success and
provided much hope for the future, his germline method of
editing the mice genomes is still not currently feasible in
humans. Thus, there are still a fair amount of hurdles this
technology must overcome before it can be used as a way to
cure DMD in people. Since the germline method is not a
realistic possibility, one of the biggest issues when applying
this technology to humans is finding an easy way to direct the
materials needed into somatic cells. There is very little issue
when injecting the system into a zygote, but more problems
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Brendan Lettrich
that will be injected into subjects are common biological
elements, and will be destroyed in the cell not long after
completing their task, consequently posing no threat to the
environment or to the humans themselves. Additionally, it
should be noted that production and storage of CRISPR carry
no threat as well, as the materials are collected from viral
DNA, and if not stored properly will simply denature [4].
While there little to no environmental risks associated
with the use of the CRISPR/Cas9 system, some viable
concerns have been raised over how the technology’s use
could bring about some unexpected negative health effects in
people. CRISPR is still early in its development, so much
more testing needs to be completed to ensure that no off-target
mutations occur, as these could potentially lead to severely
damaging health defects. Scientists are already making great
progress on this front, however, as seen by the negligible
amount of mistakes made by CRISPR in Dr. Long’s
experiment [3]. It is not just the off-target mutations that have
raised concern, though, as many critics are beginning to worry
about the unintended effects of the desired DNA cuts as well.
It is well known that many genes are pleiotropic, meaning
they can influence the expression of more than one phenotype
[12]. This means that in cutting a strand of DNA to achieve
one goal, we could accidentally lead to another change in gene
expression that was not accounted for. While this change
could be something insignificant, it could also cause a more
dangerous change that could put someone at a higher risk for
cancer, Alzheimer’s, or other diseases. With hundreds of
thousands of genes in the human genome, researchers do not
fully understand all of the functions of each and every gene,
and thus this concern is something that could lead to real
problems.
This issue is already in the process of being addressed,
however, as researchers like those at the National Human
Genome Research Institute are currently working to discover
all of these functions in order to gain a better understanding
of our genetic code as a whole. With more efficient gene
editing tools being produced, such as CRISPR, this research
can be done much faster, and thus the day when we can fully
map the function of each gene may be someday soon [13]..
As long as these issues are dealt with, the CRISPR/Cas9
system should be a sustainable genetic engineering tool that
can be used for the foreseeable future. Once again, however,
there are still more issues that must be addressed, as the
CRISPR/Cas9 system has raised a few ethical concerns as
well.
now the risk of gene editing is considerably higher than the
reward because more research and testing still needs to be
done. The CRISPR/cas9 system is no exception to this [10].
Scientists have just recently begun testing on human embryos
and many scientists like Jennifer Doudna, one of CRISPR’s
biggest supporters, still think that it’s too early to start human
testing [6]. However, coupling the limitless potential of
CRISPR with the vast quantities of money that could be
profited from it, there is a very strong chance that some
wealthy, powerful people could begin pushing for it to be used
in practice.
An Imperfect Technology
According to the Journal of Clinical Research and
Bioethics, the first major concern with the CRISPR/cas9
system is the risks and consequences compared with the
reward. The CRISPR/cas9 system is relatively new to the
scientific world and is in the process of still being developed.
With that being said, if the system were put to commercial use
today, the results would be very unpredictable and likely
dangerous. However, the potential for the system is immense
and growing each day. The CRISPR/cas9 system has the
potential to cure several genetic diseases, such as DMD,
diabetes, and many types of cancer, maximize the food
consumers get from crops and livestock, form animal
chimeras for organ transplants, and enhance the human
genome. The vast potential of CRISPR has led to an explosion
of interest by scientists to perfect the system. However, this
can cause some scientists to disregard the safety concerns and
push for its use [14].
For instance, within the last year, a group of Chinese
researchers announced that they began their first trials on
human embryos. This shocked the science community
because most scientists believed that human testing was a few
years down the road. One specific critic, Keith Joung, who
studies gene editing and specializes in methods of tracking
down cas9’s off-target mutations, believes that CRISPR
needs to be developed more before it can be tested on human
embryos. Joung learned through his studies that the frequency
of these off-target mutations that result in genetic mutations
range from 0.1% to 60% of the time [5].
Along with the high frequency of off-target mutations,
scientists have some concern with the possibility of gene
editing in the human germline, according to the Journal of
Clinical Research and Bioethics. The main problem with
editing the germline is that even if the CRISPR/cas9 system
is used correctly and there are no mutations at the time, there
is no way to determine how the edited genome will affect
future generation. Another problem with using the
CRISPR/cas9 system to edit the germline is there is no way
to enforce informed consent. If a person agrees to having
CRISPR used on them to edit a gene in their germline causing
a disease, then a genetic mutation caused by the edited gene
could occur in a latter generation and that person suffers the
consequences of the first person’s choice. Using the
ETHICAL CONCERNS WITH CRISPR
As engineers continue to develop more advanced
technology, ethics is becoming a large aspect of engineering.
A lot of controversy spurs around gene editing in general, not
just the CRISPR/cas9 system. Per Renuka Sivapatham of the
Buck Institute for Research on Aging, many people feel as
though it is immoral to change a person’s genome. As of right
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Brendan Lettrich
CRISPR/cas9 system to edit a gene in the human germline is
still being questioned by the scientific community [14].
Accessed
1.25.2017.
http://www.nature.com/cr/journal/v26/n5/full/cr201628a.htm
l
[3] C. Long, et al. “Prevention of muscular dystrophy in mice
by CRISPR/Cas9-mediated editing of germline DNA.”
Science.
9.04.2014.
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http://science.sciencemag.org/content/345/6201/1184.full
[4] M. Specter. “The Gene Hackers.” The New Yorker.
11.16.2015.
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http://www.newyorker.com/magazine/2015/11/16/the-genehackers
[5] H. Ledford. “CRISPR, the disruptor.” Nature. 6.03.2015.
Accessed 2.08.2017. http://www.nature.com/news/crisprthe-disruptor-1.17673
[6] J. Kahn. “The Crispr Quandary.” The New York Times
Magazine.
11.09.2015.
Accessed 2.09.2017.
https://www.nytimes.com/2015/11/15/magazine/the-crisprquandary.html?_r=0
[7] “CRISPR/Cas9 Guide – Overview of CRISPR/Cas9.”
AddGene.
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2.16.2017.
https://www.addgene.org/crispr/guide/
[8] “Edit-R CRISPR-Cas9.” Tamar Laboratory Supplies, Ltd.
2017. Accessed 2.14.2017. http://www.tamar.co.il/crisprcas9/
[9] C. Nelson, et al. “In vivo genome editing improves muscle
function in a mouse model of Duchenne muscular dystrophy.”
Science..
1.22.2016.
Accessed
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http://science.sciencemag.org/content/351/6271/403
[10] G.H. Bruntland. Chapter 2. Our Common Future:
Report of the World Commission on Environment and
Development.
3.20.1987.
Accessed 3.24.2017.
http://www.un-document.net/ocf-02.htm
[11] E. Rodriguez. “Ethical Issues in Genome Editing Using
Crispr/Cas9 System.” Journal of Clinical Research and
Bioethics.
3.24.2016.
Accessed
1.10.2017.
https://www.omicsonline.org/open-access/ethical-issues-ingenome-editing-using-crisprcas9-system-2155-96271000266.php?aid=70914
[12] “Pleiotropy.” Natural Living Center. 2011. Accessed
3.26.2017.
http://www.naturallivingcenter.net/ns/DisplayMonograph.as
p?StoreID=b571dewxvcs92jj200akhmccqa7w8v75&DocID
=genomic-pleiotropy
[13] “An Overview of the Human Genome Project.” National
Human Genome Research Institute. 12.27.2012. Accessed
3.25.2017.
https://www.genome.gov/12011241/thecompletion-of-the-sequence-and-remaining-goals/
[14] R. Sivapatham. “Ethical Implications of Human Genetic
Engineering.” SAGE Buck Institute. 8.19.2015. Accessed
2.10.2017. http://sage.buckinstitute.org/ethical-implicationsof-human-genetic-engineering-2/
The Creation of a Superior Few
A second major concern with the use of CRISPR/cas9
to edit a person’s genome is the effect it would have on society
as a whole. Gene editing tools would be very expensive to
use, so people tend to believe that CRISPR is only accessible
to the wealthy. The gap then between the poor and the wealthy
would increase because only the wealthy would be able to
afford using CRISPR to cure a disease. Also, at first CRISPR
is mainly used for curing genetic disease, but it has the
potential of editing genes that detail other aspects of a
person’s body. CRISPR could be used to enhance a person’s
athletic ability, height, eye color, hair color, etc. [11]. This
worries people because the price of gene editing would be
very high and only available to the wealthy. Although this
may seem far-fetched to some, this could eventually lead to
the creation of a superior few or race of sorts. Those who
could afford it could use CRISPR’s abilities to enhance
themselves genetically, perhaps by developing greater
intellectual capacity [11]. While the technology is years away
from potentially being able to accomplish such a task, even
the distant future must be considered when weighing the
benefits and consequences of something as revolutionary as
CRISPR.
FUTURE OF CRISPR
Although other gene editing tools have been used in an
attempt to develop cures for genetic diseases, CRISPR has the
potential to be one of the most impactful systems in the
biomedical engineering field. Dr. Long’s experiment could
potentially set the foundation for the endless possibilities for
the CRIPSR/cas9 system. If Dr. Long is able to develop a way
to cure DMD with CRISPR, it could be modified to then cure
several other complex genetic diseases such as Alzheimer’s
disease, cancer, AIDS/HIV and many more. However, the
uses of CRISPR do not stop at just curing diseases, CRISPR
could potentially be used for genetically modifying crops and
livestock to reap the maximum amount of food and nutrients.
Along with that, CRISPR can be used to genetically modify
animals to carry human organs that include hearts, kidneys,
and lungs, all of which are in high demand. In the end, the
uses of CRISPR are endless and the impact it can have on the
medical world is unmeasurable.
SOURCES
[1] “Duchenne Muscular Dystrophy (DMD).” Muscular
Dystrophy Association. 2017.
Accessed 2.15.2017.
https://www.mda.org/disease/duchenne-muscular-dystrophy
[2] J. Mendell.
“Duchenne muscular dystrophy:
CRISPR/Cas9 treatment.”
Cell Research. 3.01.2016.
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Kris Keppel
Brendan Lettrich
ADDITIONAL SOURCES
D. Kostos. “CRISPR Gene Editing: The Future & Ethics of
Engineering in our World.” 8.31.2016. Accessed 1.09.2017.
http://www.jove.com/blog/2016/08/31/crispr-gene-editingthe-future-ethics-of-engineering-our-world
J. Kozubek. “How Gene Editing Could Ruin Human
Evolution.”
Time Magazine.
1.09.2017.
Accessed
1.24.2017.
http://time.com/4626571/crispr-genemodification-evolution/
H. Ledford. “CRISPR: gene editing is just the beginning.”
Nature.
3.07.2016.
Accessed
1.09.2017.
http://www.nature.com/news/crispr-gene-editing-is-just-thebeginning-1.19510
ACKNOWLEDGEMENTS
We would like to acknowledge our writing instructor
Diane Kerr and our co-chair Andja Potknojak for their
assistance in creating this paper. They provided great
feedback throughout the process that allowed us to make this
paper the best that it can be. Additionally, we would both like
to thank our respective floor mates and engineering peers for
providing support and empathy for the last few months.
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