Peiwei Chen Wins Harold M. Weintraub Graduate Student Award

Peiwei Chen, who will receive his PhD in biology from Caltech in June 2024, has been awarded the Harold M. Weintraub Graduate Student Award by the Fred Hutchinson Cancer Research Center. A total of 12 graduate students in the United States and abroad received the honor in 2024.

The Weintraub Award honors Harold "Hal" Weintraub, a molecular scientist at the Fred Hutchinson Cancer Center, who passed away in 1995 and was known as an "extraordinary mentor, colleague, collaborator and friend," according to the center's press release.

Chen grew up in mainland China and went to college in Hong Kong. He has spent the past seven years at Caltech working in Professor of Biology Alexei Aravin's lab on genome defense against selfish genes, such as transposons, the so-called "jumping genes."

"We usually think of genes as good, and only when they mutate are we faced with diseases or other problems," Chen explains. "But there is actually a lot of conflict within our DNA. These selfish genes persist not to benefit the entire organism, but just to propagate themselves."

Selfish genes "cheat" to enhance their survival in one of two ways: by increasing their copy numbers and proliferating more than other genetic elements, or through a mechanism called transmission distortion. "Normally, you get one copy of DNA from your mother and another from your father, and then when you have children, you pass one of the two copies randomly, so there is about a 50/50 chance that these genes make it to the next generation," Chen says. "But if genes are selfish, they can try to sabotage the inheritance of the other copy, to outcompete it. If they succeed, they will be inherited almost all the time."

This phenomenon can occur anywhere on the genome. For example, half of a typical man's sperm will carry an X chromosome, and the other half will carry a Y chromosome. But if a selfish gene arises on the X chromosome, it may destroy all the sperm cells carrying Y chromosomes. "This is detrimental to the host—the man, in this case—because the number and the diversity of his progeny is cut in half," Chen says. "But it's good for the selfish gene's survival."

Selfish genes are almost always present in DNA, but most of the time they are silenced or controlled, including through what is known as the piRNA pathway, which Chen studies. The piRNA pathway is a short stretch of RNA that recognizes selfish genes and guides them along a path that will eventually silence their expression. Consequently, although the selfish gene may be successfully transcribed, it never becomes a fully functional protein because it is stopped halfway through by the piRNA pathway.

Chen will begin a postdoc at Cornell University this fall, where he will explore selfish genes and the mechanisms that protect against them in a broader variety of species. He hopes to study insects in the future, such as ants. "As scientists, we often look at so-called model organisms, like mice or flies, where we've gained some very deep mechanistic insights," Chen explains. "But we lose the breadth and diversity of biology if we don't look beyond these organisms. I'm hoping that by looking elsewhere on the tree of life, places that haven't received as much attention, we may gain insights that are more broadly applicable to understanding biology."

Chen says he is "over the moon" with respect to winning this award. "We are all trying to do good, interesting work, but when you're recognized, you begin to think that you're not the only one who finds it interesting, and that's a wonderful feeling," Chen says. "It can be easy to forget how important curiosity-driven science is. This award has helped me remember what a privilege it has been to pursue my curiosity without worrying about much else. I feel very lucky to be in a position to ponder, to wonder, to get lost thinking about things I've never thought about before. That's when the magic happens."