Kendal Gast
3-22-16
ENGL 355
CRISPR/Cas and the Crispy
Road Ahead
The
human race has reached a tipping point.
Or one could argue that we humans have reached several tipping points (realizations)
and already forgotten them, only to continue and perhaps, remember, again. The ability to edit the human genome is
hailed by some as the next step in human evolution or a gross overestimation of
our hasty, naïve ambition. Clustered
Regularly Interspaced Short Palindromic Repeats (CRISPR) is a bacterial defense
mechanism that has been altered in a way to effectuate genetic engineering
(eugenics). This technology should only be
utilized to cure genetic disease, but not used to enhance humans or modify
diseases. CRISPR calls into question
what it means to be human, and in the future will need a necessary
redefinition.
CRISPR
was first identified as a bacterial acquired immunity function. Scientists noticed repeated segments of DNA,
the palindromic portion of the acronym, in bacteria. These repeated segments were separated by
different, unique patterns. These unique
patterns (protospacers) were observed to be copies of viral DNA the bacteria
encountered (Addgene). A short distance
away from these repeats, genes that code for proteins called “CRISPR associated
proteins” or Cas were found (Addgene). The
process of defending against known viruses begins by transcribing part of the
CRISPR system (or several protospacers), into which becomes pre-CRISPR RNA
(Addgene). The pre-crRNA is then
separated into individual crRNAs by trans-activating crRNA (tracrRNA), which in
turn brings along RNase III (a ribonuclease) and Cas enzymes to help separate
the pre-crRNA (Addgene). The tracrRNA and Cas enzymes combine with the
individual crRNA strands to form unique complexes (Addgene). These complexes then look for complimentary strands of the crRNA, or
known sequences of viral DNA. In order
for the complexes to bind to the viral DNA, Protospacer Adjacent Motifs (PAM) must
be after the crRNA site (Addgene). Once
the crRNA is matched, the Cas nuclease snips the DNA in both places after the
PAM. (Addgene). Put a little more
simply, a large section of the CRISPR system in the bacterial DNA is
transcribed. Similar protospacers (not a
part of the original DNA) work with a ribonuclease and Cas enzyme to break up
the large section of this CRISPR system into smaller segments. These segments then bind with the similar
protospacers and Cas enzyme to identify the portion of viral DNA to break it,
rendering it unusable. This process
occurs naturally in prokaryotic cells, while the cleverness of human scientists
(eukaryotic organisms), in modifying this process, but has been adapted to work
in mammalian cells - and even fertilized eggs.
Scientists
can edit DNA sequences in eukaryotic cells by combining crRNA and tracrRNA into
a single guide RNA as Rath et al. point out in Biochimie (125). This allows
for a double strand break in DNA when the new guide RNA and target DNA match up
(Rath et al. 125). There are then two
ways in which the DNA strand can be repaired: Non-Homologous End Joining (NHEJ) or Homology
Directed Repair (HDR). NHEJ simply joins
the two ends together with a few pairs or deletes other bases to continue the
pattern (Rath et al. 125). This can
result in poor functioning of the cell or render the DNA strand obsolete. HDR, on the other hand, uses another strand
of DNA that matches up with both broken ends of the strand (Rath et al. 125). CRISPR is also able to facilitate multiple
strand breaks at once, thus giving scientists the ability to insert several
different pieces of DNA or removing large portions of the sequence
altogether. Although this method is much
more efficient and precise, compared to just four years ago, it is nevertheless
limited by the need of specific PAM sites to direct the Cas enzymes (Rath et
al. 125). CRISPR has fundamentally changed
the way scientists conduct everyday eugenic research, yet accrediting the
proper individual or group for inventing the technology has proven difficult.
The
Broad Institute and University of California Berkeley are the two main institutions
trying to patent the CRISPR/Cas system. As
Tony Fong writes, “In April [2014], the US Patent and Trademark
Office issued the first patent, No. 8,697,359,
for the CRISPR-Cas9 system to the Broad Institute” (Genomeweb). Because of this, Feng Zhang of the Broad
Institute founded Editas Medicine in November 2013 with UC Berkeley scientist
Jennifer Doudna, among others (Fong).
Having cooperating scientists claim that they each invented the
technology makes it harder to award patents, difficult to utilize the
technology, and also not make any sense. On top of all this, Doudna gave a TED talk at
the end of last year and explicitly stated that she was the inventor of the
CRISPR technology. Things get even more
confusing because Doudna and Emmanuelle Charpentier, professor of Hannover
Medical School in Germany, co-authored a paper in August 2012 after working
together and sharing data on Cas enzymes (Fong). Then, of course, Charpentier told The Independent that she came across the
technology first (Fong). A number of
other institutions have filed patents parallel to the CRISPR system before any
of these notable scientists came on to the scene (Fong). The Broad Institute’s application could be
limited by an approval of UC Berkeley’s application, which will have effects in
how CRISPR develops and is distributed for wider use after the USPTO decides
what to do. Garden-variety scientists
know more about how this system functions in such a short amount of time and
somehow immediately see the profitable applications a technology this powerful
has to offer. Because of CRISPR’s far-reaching
and relatively unknown future, Doudna and other think tanks have voiced their
concerns about human applications, especially anything to do with human
embryos.
Perhaps
what is most disturbing about a gene editing technology is the uncertainty it
brings. Human beings have only recently
discovered the ability to manipulate DNA directly, and luckily it has been too
difficult to change human DNA. Gretchen
Vogel writes that in 1975, scientists, policymakers, and lawyers gathered at Asilomar,
California to “craft[ed] guidelines for research
that altered the DNA of living organisms” (1301). Back then, the idea of altering human DNA
seemed too extraordinary for the current moment then. In January of this year, Doudna organized a
similar meeting, albeit smaller, of experts to discuss guidelines for the safe
and ethical use of CRISPR methods (1301).
Two group commentaries published in Science
and Nature both asked for serious
consideration of action before any scientist attempts to modify human DNA for
clinical uses (1301). In the Nature commentary, the authors asked for
a complete prohibition “on any experiments that involve editing genes in human
embryos or cells that could give rise to sperm or eggs” (1301). Doudna and co. on the other Science hand, do not insist on an
all-stop measure, but instead “strongly discourage” any attempts at human DNA
modification for “clinical applications” – with the exception of some human
cells allowed as long as no one tries to get pregnant (1301). In fact, there are no laws in the United
States or China that ban germline genetic engineering (1301). However, if one wishes to establish a pregnancy
in the U.S. using this method, it needs approval from the FDA (1301). Think tanks like the Hinxton Group have
already proposed guidelines for this type of research. Last September they released their “Consensus
Statement on Genome Editing Technologies and Human Germline Genetic
Modification” (hinxtongroup.org). It
describes very clearly 12 issues that scientists and governments need to
address if they are to continue moving forward with DNA modification
technologies, which, as the authors are already aware, will happen
(hinxtongroup.org).
But these journal articles and grand statements of issues
are too shortsighted. They miss the
point of a few years longer down humanity’s road, probably about 20 years. Several of the citations used in this paper
mentioned how easy it would be for an individual with amateur biology, genetic,
and lab knowledge to utilize CRISPR and modify nearly any cell or prokaryotic
organism they desire. That is the world
of 2016. The world of 2036 will most
likely have altered human beings at a fundamental level, and diseases as
well. Sure, scientists would have
already cured most genetic diseases by then, but why should they stop
there? At some point the human race will
have crossed the threshold of God-power.
No longer will there be a clear distinction between “humankind/man” and
“nature”. There very likely will only be
“humankind/man”. A valid argument can be
made that this is the obvious next step for humans. No longer can they plod along, wondering if
they will ever evolve into something different, better, greater. Humans will take it upon themselves to make
sure their species embodies “progress” in the absolute, most magnificent sense
of the word. Like the narrator says of
Jimmy in Oryx and Crake, “Perhaps he
failed to take seriously his own despair” (344). As do humans.
Works Cited
Addgene. Addgene.org. Oct. 2015. Web. 1 Mar 2016.
Atwood, Margaret. Oryx and Crake. New York: Anchor Books,
2004. Print.
Fong, Tony. “As CRISPR-Cas9
Technology Sets to Take Off, Uncertainty Swirls Around
IP Landscape.” Genomeweb.
Ed. Ed Winnick. 18 Jun 2014. Web. 9 Mar 2016.
Hinxton Group, The. Hinxtongroup.org. Johns Hopkins Berman
Institute of Bioethics.
3 Sept 2015. Web. 8 Mar 2016.
Rath, D. Amlinger, L. Ruth, A.
Lundgren, M. “The CRISPR-Cas Immune System:
Biology, Mechanisms, and Applications.” Biochimie 117: Special (2015): 119-
128. Web. 8 Mar 2016.
Vogel, Gretchen. “Embryo
Engineering Alarm.” Science 347.6228
(2015): 1301. Web.
8 Mar 2016.
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