Yasushi Saka: Stirring a melting pot of math and morphogens

I n a developing embryo, seemingly identical cells are directed to different fates by the combination of signals they receive. When the signals come from morphogens—extracellular molecules that spread from a localized source—the effect on a cell depends on the amount of morpho-gen it receives, with cells closer to the source receiving a higher dose. The change in morphogen concentration across a population of cells is gradual, but the boundary between one tissue type and another is not. Cells must therefore interpret the morpho-gen signals in terms of thresholds. How cells do this is the question that drives Yasushi Saka's research. As a post-doc in Jim Smith's lab—fi rst at the National Institute for Medical Research in London, and later at the Gurdon Institute in Cambridge, UK—Saka worked on frog morphogens (1, 2) and used mathematical modeling to understand how cells respond to them (3). Saka strongly believes in the benefi ts of looking beyond one's fi eld of study for answers. Before his incarnation as a developmental biologist, he was a successful yeast geneticist (4), and recently he's returned to the unicellular organism. Yeast might not be the obvious choice for answering questions about morphogen biology, but Saka believes that it could be very useful for fi lling in the gaps between frogs and math. Saka now runs a lab at the Interdisci-A fi tting home indeed. How did you get interested in science? There were no scientists in my immediate family, so I'd say I'm a bit of an oddball. My science experience was limited during childhood, although my father once bought me a cheap microscope, which I loved. I looked at things like my hair, or sand, or soil. Once I found something moving in the soil, and in retrospect, I think it was a nematode. Aha! A young C. elegans researcher! Yes, if I may say so. You went to Kyoto University. Did you study biology? Yes, but it was a peculiar system at the time. I don't know what it's like now, but back then, we could pick all sorts of subjects: biology, mathematics, physics, or whatever. Then, gradually, we focused more on one particular subject. In my case, that was biology, because I didn't really understand equations. Mathematics is not my strength. You stayed on at Kyoto for your Ph.D.? Yes, I studied the fi ssion yeast cell cycle with Mitsuhiro Yanagida. Actually, I …