The Fevers of Reason. Gerald Weissmann

defense mechanism used by many organisms against double-stranded RNA (dsRNA) viruses. Interfering RNAs have provided us with a means of selectively shutting down one or another genes in a cell and given us clues to antiviral therapies to come.

      A few months later, the names of Fire and Mello joined those of other American laureates carved into a pink granite monument at the corner of Columbus Avenue and 81st Street in New York. The monument, dedicated to Alfred Nobel and to American Nobel laureates past and present, stands behind the American Museum of Natural History in a park named after Theodore Roosevelt, the first American laureate (Peace Prize, 1906). The names of 290 other American Nobel prize–winners have been inscribed on the sides of the monument, and there is ample space for more to come.

      The monument in New York came to mind as I read Craig Mello’s conversation with Adam Smith of the Nobel Foundation, who called Mello right after a call from Stockholm had given Mello the news of his award on October 2, 2006.

[ADAM SMITH]:	Well first of all many, many congratulations on being awarded the prize.
[Craig Mello]:	Thank you so much.
[AS]:	Where were you when you heard the news?
[CM]:	I was checking my daughter’s blood sugar. She has type 1 diabetes so I was actually up, one of the few, I guess, in the North Americas who was awake.
[AS]:	Yes, I imagine so.
[CM]:	We check her frequently and I just happened to be up, checking her blood sugar. And she had a good sugar actually, 95, which is normal.
[AS]:	That’s good news, yes.
[CM]:	I was on my way back to bed and the phone rang.
[AS]:	So two good pieces of news at once! I imagine you were thinking of other things but what was your first thought on being told?
[CM]:	Well, you know, gee, that’s a really hard question! You know first it’s disbelief, and I don’t think it sinks in quickly. I felt I was sort of too young to get it this soon and thought, if it happened . . .

      “This soon” and not later, 46-year-old Mello joined other striplings whose names were carved in granite, among them Joshua Lederberg and James Watson (ages 33 and 34, respectively, when they received their notifying telephone calls).

      The Nobel monument was a recent addition to the New York scene. The slab was unveiled on a damp October day in 2003 by Mayor Michael Bloomberg, with appropriate remarks by Swedish and Norwegian dignitaries, choral music, and a stirring address by Eric Kandel (Physiology or Medicine, 2000), who paid tribute to the city’s public school system, of which he was a product. In the audience were many Nobel prize–winners, their guests, consular and civic officials, and platoons of students from high schools in the neighborhood.

      As the flock of VIPs dispersed, a teenaged couple made its way to the monument. Arm draped around his girlfriend’s shoulder, a gangly youth pointed up at the open space under all those names: “I’m going to be the first black guy up there in science!”

      That’s why we have prizes and monuments, I thought at the time. To carve something in stone for a kid to look up to.

      THE STORY OF dsRNA-MEDIATED gene silencing wasn’t always carved in stone for a kid to admire. The work of Mello and Fire bears the hallmarks of a “seminal discovery,” a term usually applied in retrospect and of three aspects. First, the unexpected often comes from a field far removed from the scientist’s own field of expertise. Next, it stares one in the face, unexpectedly, like Mendel’s sweet peas or Darwin’s finches. Finally, it tips its hand when the seminal publication uses key words like “unexpected” or “surprise” in title or abstract. Here’s how siRNA (small interfering RNA) was announced in the 1998 paper that Fire, Mello, and others published in Nature: “To our surprise, we found that double-stranded RNA was substantially more effective at producing interference than was either strand individually.”

      While the role of siRNA-mediated gene silencing is now written in stone, the path to its discovery was by no means straightforward: it began with petunias, led to worms, then finally on to yeast and beast. Andrew Fire recalled in his conversation with Adam Smith, “Well, we were led to it pretty much by our experimental noses. The people in the plant field had done tremendous work on gene silencing and so we, sort of, were following in their footsteps in trying to sort out what was responsible for this weird silencing phenomenon in the worm.”

      Their experimental noses had a long trail to sniff. Deciphering what George Sen and Helen Blau called “the silence of the genes” began with decoding the color purple in petunias and has wound up producing compounds of promise in disease. In 1990, plant scientists Carolyn Napoli, Christine Lemieux, and Richard Jorgensen were studying the formation of anthocyanin, the pigment that makes petunias purple. Testing whether the enzyme chalcone synthase was the protein critical for the color purple, they overexpressed chalcone synthase (CHS) in petunias. In their paper they wrote, “Unexpectedly the introduced gene created a block in anthocyanin biosynthesis,” and 42% of the plants became white or had chimeric purple–white patterns. They had silenced the gene for CHS, and this silencing proved to be heritable: “progeny testing showed that the novel phenotype co-segregated with the introduced CHS gene.” Purple no longer, by heredity.

      Sure enough, “unexpectedly” was the operative word in the petunia paper, and the work it described led directly to Fire and Mello’s “surprise” at finding double-stranded RNA interference in worms. Many viruses contain double-stranded RNA, which, when injected into a cell, binds to a complex series of proteins (one called Dicer) that degrade viral RNA, and so the cell survives the infection.

      These days, when I pass by that monument on Columbus Avenue, I’m reminded of petunias, and all those messages sent by “phone lines, email connections, and delivery services between Baltimore and Worcester.” Going viral, indeed.

      PLANNING FOR THE NOBEL MONUMENT in New York began with discussions in December 2001, when the Nobel Foundation celebrated its centenary in Stockholm. Most of the living Nobel laureates in Physiology or Medicine (including a good number of Americans: Joshua Lederberg, Barry Blumberg, Alfred Gilman, Joseph Goldstein, Michael Brown, Eric Kandel, among others) showed up to revisit their grandest moment. The occasion was celebrated by lectures, symposia, concerts and the grandest of all banquets in Stockholm’s splendid Town Hall. My wife and I were guests, and we were lucky enough to have been seated at the banquet table with the senior American laureate present, Tom Weller of Harvard (1915–2008). He told a story that described one way to make a great discovery: make a great error, and correct it.

      Over wines of not inconsiderable vintage, Weller reminded his dinner companions that the first time American scientists had been feted in this hall, it was for a dazzling cure based on luck and error. In 1934, two Harvard clinicians, George R. Minot and William Murphy, joined George C. Whipple, a Rochester pathologist, on the podium in Stockholm. From the wrong animal model, they had found a cure for pernicious anemia.

      George Richards Minot, a patrician Bostonian, had been a professor of medicine at Harvard since 1928. He also maintained an active private practice oriented to hematology. William Parry Murphy, on the other hand, was a Westerner of decidedly nonpatrician stock. After one year at the University of Oregon Medical School he won a scholarship to Harvard Medical School, graduated in 1922, and in the midst of his Boston residency Minot made Murphy an offer he could not refuse.

      Minot, as the story goes in Medicine at Harvard, was accustomed to picking young physicians of Peter Bent Brigham Hospital as associates to run his office practice, which consisted in good part of patients with diseases of the blood—and with homes on Beacon Hill. As senior resident, Murphy was next in line for this plum job, but it was customary for the young men to earn their