In September 2018, just a few weeks after receiving the Kavli Prize in Oslo, Charpentier flew to New York to deliver a memorial lecture at Columbia University.29 As usual, her appearance attracted a packed house, as hundreds of students and faculty crammed into the auditorium including the gangly figure of Nobel laureate Richard Axel. Arriving late, the eminent neuroscientist folded himself into a front row seat, as intrigued as everyone else to hear the petite Frenchwoman on course to follow his journey to Stockholm. After an interminable introduction, Charpentier politely chided her host for exaggerating her resume. “I did not publish that many papers!” she said. “I’ve always been more on the perfectionism side—I focus more on the quality than the quantity.”
In her book, Doudna said her first impression of Charpentier was “soft-spoken and retiring.” That was a fair reflection of Charpentier’s lecture, a surprisingly subdued account of her CRISPR journey, framing her work in the context of legendary French molecular biologists like François Jacob and Jacques Monod. She dwells on a quote from Monod in 1970:
Modern molecular genetics offers us no means whatsoever for acting upon the ancestral heritage so as to improve it with new features—to create a genetic “superman”: on the contrary, it reveals the vanity of any such hope: the genome’s microscopic proportions today and probably forever rule out manipulation of this sort.30
Charpentier seldom looks up at the audience and strikes me as guarded, reluctant to let loose and share stories. Axel fidgets in the front row. She wonders if her own mobility “helped me to understand the way bacteria defend themselves against mobile elements.” It’s more a statement of fact than an attempted joke. But if humor is in short supply, humility is not. Charpentier acknowledges a crucial slice of fortune. For years the pet organism in her lab was a bacterium called Streptococcus pyogenes, which can cause life-threatening infections. This was the source of the Cas9 protein. “Cas9 in Strep pyogenes is very efficient,” Charpentier said. “We’ve tested other Cas9 proteins, some are close in efficiency, but if we’d identified mechanisms in another bacterial species, I’d not be here in front of you.”
After her lecture, Charpentier fields questions from the audience: She bemoans a recent European court ruling on GMOs (“a big disappointment for scientists in Europe”) and dismisses concerns about CRISPR’s safety. “Delivery is a bigger bottleneck than the CRISPR mechanism itself,” she says confidently. Students line up to take selfies with her; she is a bona fide scientific celebrity after all. I join the queue to invite Charpentier for an interview before she heads to dinner with some university VIPs.
The next morning, we rendezvous on Manhattan’s Upper West Side. She arrives looking chic in blazer and jeans, two months shy of her fiftieth birthday. By contrast, I am sporting fresh Central Park pigeon excrement down my laundered white shirt. “It is good luck, I think,” she smiles, as we head to a nearby French bistro.
Charpentier was born fifteen miles south of Paris in 1968, six months after the student protests and civil unrest. From an early age, she was intent upon going to college, inspired by her older sister. Her father taught her the Latin names of plants, which might have inspired her to pursue biology. At age twelve, Charpentier came home from school one day and told her mother that she would eventually study at the Pasteur Institute. Ten years later, she made good on her promise. “I got my worst grade for [microbiology] and it became my specialty!” she laughs. She earned her PhD in microbiology in 1995, writing her thesis in a library overlooking the Cathedral of Notre-Dame.
Charpentier recognized that life as a research scientist “would fit the many aspects of my personality—my curiosity, intellectual drive for knowledge, enjoyment of communicating knowledge to others, and working as a team, and my desire to turn complex scientific discoveries into practical applications that would help society.”31 She spent the next six years in the United States, beginning at the Rockefeller University in New York. She studied bacteria responsible for skin infections in mice, searching for new biochemical pathways and drug targets. After working with Streptococcus pneumoniae, she turned to S. pyogenes, which became her favorite organism. Her experience in America introduced her to many talented researchers, many with a strong entrepreneurial spirit. That lesson, too, was not lost on her.
There were no openings at the Pasteur when she was ready to return to Europe, but she landed at the University of Vienna in laboratories named after the Nobel laureate Max Perutz, a contemporary of Crick and Watson.IV “It was important to be independent and to not have anyone around me,” she said. I’m intrigued by Charpentier’s willingness to travel in search of freedom and funding. Without missing a beat, she says: “In twenty-seven years, I’ve worked in five countries, seven cities, ten institutions. Fourteen different offices, thirteen different departments, and fourteen apartments. It’s a very big turnover!” Each move was motivated by an incentive or a better position.
Charpentier’s first exposure to CRISPR came in 2006. Two of her students, Maria Eckert and Karine Gonzales, were performing computer searches for DNA sequence matches similar to the studies reported by Mojica one year earlier. This time CRISPR was not the bait but the prize. Eckert and Gonzales were scouring the S. pyogenes genome for traces of small RNAs (encoded by genes that produce RNA molecules rather than proteins). One of the most abundant hits was a novel trans-activating CRISPR RNA (tracrRNA). The gene encoding this tracrRNA sat in the vicinity of the CRISPR array, although the significance of that location wasn’t immediately obvious. Charpentier’s major interest was not CRISPR or bacterial immunity, but her tracrRNA had a certain je ne sais quoi. It would prove a critical piece of the genome editing puzzle.
In 2008, Charpentier decided to leave the history of Vienna for the hinterland of northern Sweden and Umeå University. The weather was bleak but Charpentier warmed to the atmosphere and people at the Laboratory for Molecular Infection Medicine Sweden. She focused on tracrRNA, collaborating with German biochemist Jörg Vogel, planning experiments on the flights back and forth to Sweden.
The next year, her group established a link between the CRISPR-Cas9 system and tracrRNA. “It was a very simple experiment,” she recalls. When the group knocked out tracrRNA, they found that the CRISPR RNA (crRNA) was not made, and vice versa. The logical conclusion was that Cas9 formed a physical complex with these two RNA molecules. When Charpentier’s team compared tracrRNA sequences from a variety of bacteria, they found one thing in common: a sequence that forms a duplex with crRNA. While other groups were describing more complex types of CRISPR systems, the beauty of the type II system in S. pyogenes was that only a single gene, Cas9, was necessary for viral interference, along with crRNA. And then there were three. Charpentier and Vogel had brought the third component—tracrRNA—into the story. “Yes, it is an essential component, because Cas9 is an enzyme guided by two RNAs,” she said.32
One month after Charpentier submitted her polished account of the discovery of tracrRNA to Nature in September 2010, she traveled to the Netherlands to give a talk at the annual CRISPR conference, which had ballooned to about two hundred CRISPR aficionados. Few members of the CRISPR club knew about the French scientist working in Sweden with colleagues in Austria and Germany. But now, Charpentier recalled with a smile, “they discovered the famous story of tracrRNA.” It was the pinnacle of Charpentier’s career to date. “The pioneers all came up to me and shook my hand and said, ‘I think you got the story!’ ” One notable absentee was Doudna, whose research wasn’t consumed by CRISPR just yet.