Sunday Article 04: Women In CRISPR
The 2020 Nobel Prize in Chemistry was awarded to Emmanuelle Charpentier and Jennifer A. Doudna ‘for the development of a method for genome editing.’ This was not only in recognition of the accomplishments of these scientists, but represents a victory and possibly a beginning of a new era for all female scientists.
The CRISPR-cas9 system is a precise, elegant, sophisticate, and yet efficient genome-editing tool. It left in its wake, a whole host of female-led Biotechnology companies and start-ups that have been estimated to reach a market value of $5.3 billion by 2025, according to Ahead Intelligence.
Before I continue, I should highlight a disclaimer that this in no way diminishes the accomplishments and milestones achieved by our male counterparts in the development of CRISPR. In fact, both Charpentier and Doudna has relentlessly attributed this win to the work done by all the students and researchers in their labs, regardless of gender. What makes this win stand out is, of all 916 Nobel Laureates, only 56 have been women, with the majority being literature and peace prizes, only 19 have been women scientist. The implications of this reality can be difficult to comprehend but nonetheless has cemented itself as a beacon of inspiration in an industry that has struggled to address its lack of gender diversity.
What is CRISPR?
The CRISPR-cas9 system comprises of 2 components:
The Cas9 protein that forms double-strand breaks in the genome and,
the guide RNA that interacts with, and guides the cas9 molecular scissors to ‘cut’ at the precise, pre-determined position.
By altering the sequence of the guide RNA, researchers are able to target different regions of the genome. The flexibility and its precise ability to determine where the cut will be placed in the genome are qualities that have never been seen, to such a high standard, in other genetic tools.
Diagram: © Johan Jarnestad/The Royal Swedish Academy of Sciences
Discovery of CRISPR, and the Women behind it
Jennifer A. Doudna (left), Emmanuelle Charpentier (right)
The CRISPR sequence was first identified in 1987 in E.coli, but it was Charpentier that discovered the crucial final piece to the CRISPR-cas9 system, the tracrRNA. However, the simple elegance of CRISPR-cas9 is not mirrored in the path of its discovery. It was the work of many other prominent scientists in the field that enabled Charpentier and Doudna to exploit what was once a bacterial immune response, into one of the most powerful genome-editing tools today.
Charpentier’s group was performing small RNA sequencing on the pernicious human pathogen, the Streptococcus pyogenes. This bacteria is commonly known as ‘flesh eater’ infects millions of people, causing infections such as tonsillitis and impetigo. They discovered a very well expressed RNA, which they termed tracrRNA. This RNA seemed to be encoded in the vicinity of the cas (CRISPR associated) protein-coding gene, that has two nuclease domains. The trans-activating CRISPR RNA or tracrRNA is able to form a duplex with the CRISPR RNA (crRNA) and guides Cas9 to its targets.
As a seasoned veteran in the field of regulatory proteins and RNA research in bacteria, Charpentier was well aware of the lack of precise tools in genetics and often had to improvise to develop new tools as she went along. Hence, when she saw the potential of the CRISPR-cas system, she immediately recognized the importance and impact that it would have in the field.
This prompt a meeting between Charpentier and Doudnawhile both of them were attending a conference in Puerto Rico. The collaboration resulted in the conception of the gene-editing tool we know today. Fast forward a few years, and they successfully fused the crRNA and tracrRNA, simplifying the system and producing what we now call the ‘guide RNA’.
The CRISPR-Cas system, an Ancient Immune System
The CRISPR genetic sequence was first identified as a repetitive DNA sequence that is surprisingly well preserved in a vast assortment of different bacteria and archaea. This code appeared over an over again, separated by different unique sequences that matched the genetic code of various viruses. It has been described as ‘the same word being repeated between each unique sentence in a book’. The arrays of repeated sequences were termed clustered regularly interspaced short palindromic repeats, abbreviated as CRISPR.
It was later discovered that CRISPR was part of an ancient bacterial immune system that succeeded in fending off viral infection by adding a piece of the virus’ genetic code into its genome as a memory of the infection.
The repeating CRISPR sequence interspaced by various viral DNA forms the CRISPR DNA (crDNA), and it is transcribed into a pre-crRNA. The tracrRNA (discovered by Charpentier) then binds to the repeating sequence, promoting the recruitment of the ‘molecular scissors’ Cas9. This is followed by an activation process, that includes the cleavage of the pre-crRNA into shorter fragments, by RNase Ⅲ.
The final genetic scissors consists of a CRISPR array and a single viral DNA sequence which guides the cas proteins to the invading virus upon the second infection. The cas protein will then disarm the virus by inducing a double-strand break.
There is no end to the applications of this technology, especially with the emergence of personalized medicine. The CRISPR/Cas9 genetic scissors are able to rewrite the code of life with extremely high precision and have greatly reduced the cost and time needed in therapies that revolve around gene-editing. Examples include 1. the elucidation of new cancer therapies, 2. the potential of curing genetically inherited diseases such as sickle cell anaemia, 3. developing crops that can withstand pest, mould and drought more effectively, and 4. the ease in investigating the functions of different genes and their possible role in the progression of diseases.
Women in CRISPR
As mentioned earlier, there is an unusual phenomenon where the world saw an explosion of women in leadership positions in CRISPR-based projects worldwide.
(left to right) Rachel Haurwitz, Nicole Gaudelli, Janice Chen
Some examples include Nicole Gaudelli, the senior scientist at Beam Therapeutics. The technology behind Beam Therapeutics (a modified CRISPR system) was designed by Nicole as a postdoc. Her company aims to correct diseases that are caused by point mutations, such as β-thalassemia, sickle cell disease and other hematologic and liver diseases. Nicole told C&EN that due to the history of the development of CRISPR, “people drawn to the field are more comfortable with women in leadership.”
Another stand-out in the field is Janice Chen, the Chief Technology Officer of Mammoth Biosciences. Her focus is on producing a CRISPR-based diagnostic system that has a readout as simple as a pregnancy test. The development of such technology will have large targeted implications in forensics, environmental monitoring and the detection of infectious disease agents. Additionally, Rachel Haurwitz, the cofounder of Caribou Biosciences, a company spun out of Doudna’s lab in 2011, uses CRISPR to engineer immune cells called T cells, to attack cancerous cells.
Altogether, the three companies accumulated an estimation of 331 million dollars of funding as of March 2020. When prompted, Janice also told C&EN that seeing women succeed has changed the way she looked at opportunities. However, Rachel points out that this may be a chance of circumstance. As “there isn’t 30 years of history [of CRISPR], so there isn’t 30 years of experienced white men to be hired into these positions, that leaves the door open.”
Charpentier and Doudna’s accomplishments are not unlike that of Beth Harmon, the protagonist in the Netflix original series ‘The Queen’s Gambit’. The coming-of-age story commemorated with Beth mercilessly emerging victorious in a room overwhelmingly filled with men, earning the respect of her peers and garnering the adoration of a whole new nation of fans.
This victory in no way belittles or condemns the contribution of male scientists, but rather achieves something that’s should have been established decades ago. Charpentier and Doudna have given young girls something even more valuable than a Nobel prize, they have given us the courage to dream.
Ashley, a gay black man and a poet, who grew up in the rural south of the United States in the 1930s once said, “ If you never seen someone who looks like you being who you could be, it’s very difficult to dream. It’s very difficult to imagine yourself as a poet, it there are no poets in your world.”
References:
https://www.nobelprize.org/prizes/chemistry/2020/press-release/
https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/crispr-timeline
Illustrations
© Johan Jarnestad/The Royal Swedish Academy of Sciences
This article is prepared by Emily Ng.