Photograph by: Michael Schmelling
Aleksandra Walczak has come full circle. The young researcher was, from the beginning, fascinated by biology, but felt overwhelmed by "its vastness and its details." So years ago she decided to pursue a career in physics instead. As she advanced in her studies, what most interested her was studying the physics of systems with many different interacting parts. Ironically, Walczak found a system to explore in biology. Today, Walczak is using her physics expertise to shed light on the operations of gene networks—the systems through which proteins coded by some genes control the activity of others. Their complex interactions govern life itself, and Walczak's unconventional approach to them could help scientists unravel fundamental mysteries about how the genetic code gets expressed and regulated.
Gene expression is based on the binding of proteins to nucleic acids. Because there are a small number of proteins and binding sites, gene networks are noisy systems, and their behavior is hard to predict. "Whenever you have a small number of elements, it's not certain that they will interact," says Walczak, a postdoctoral fellow at the Princeton Center for Theoretical Physics. The standard chemical descriptions of these networks simplify them by ignoring some of the sources of randomness, and Walczak believed that they might not always be a very good description of their behavior. So she decided to describe the potential interactions of proteins and genes using a model she borrowed from statistical physics, adding in more of the variables present in a living cell.
The approach allowed her to better account for and approximate cellular noise. And it made clear that gene networks can exist in far more possible states than other models had predicted. For instance, a genetic toggle switch can also exist in intermediate states, she showed, because the kinetics of the transition from "on" to "off" are so slow. Her approach to studying the molecular basis of these gene systems could help scientists paint a far more accurate picture of the intricate workings of a given network and the patterns they produce. Further yet, Wolczak's work could help reveal how these regulatory systems evolve, refuting the notion that scientists have been unable or afraid to understand the workings of what some critics have called Darwin's black box.
Listen: a discussion with Aleksandra M. Walczak
