Science-2011-Leslie-The_Power_of_One - NEWSFOCUS Small...

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7 JANUARY 2011 VOL 331 SCIENCE 24 1) Measure out a heaping portion of cells. 2) Grind until thoroughly mixed. 3) Analyze. Cellular studies still pretty much stick to this traditional recipe, whether the goal is prob- ing bacterial metabolism, following differen- tiation of stem cells, or tabulating gene activ- ity in tumors. But mashing up a multitude of cells—one common method of studying gene expression typically requires more than 10,000—obliterates key differences between cells, researchers have come to realize. “If you take an average of a large number of cells, you get an average answer,” says analytical chem- ist Renato Zenobi of the Swiss Federal Insti- tute of Technology in Zurich. That’s why more and more scientists are opting for the alternative approach of tak- ing the measure of individual cells. Although much of this work is in its early stages, “there is an increasingly diverse set of examples where single-cell studies have provided quali- tative insights that couldn’t be obtained from population-level studies,” says biophysicist Michael Elowitz of the California Institute of Technology in Pasadena. Scientists have already recorded the most accurate measurements of how much an indi- vidual cell weighs and gauged how much oxygen one requires. They’ve flagged spe- cifi c cancer cells resistant to chemotherapy and developed ways to pinpoint rare, disease- causing bacteria among swarms of harmless microbes. Developmental biologists have tallied gene activity as a fertilized egg starts its course of division and specialization, work that might help clarify the factors that spur a cell in the embryo to become one tissue and its seemingly identical next-door neighbor to become something else. And Elowitz and other researchers have spelled out how indi- vidual cells not only cope with but actually benefi t from “noise,” random fl uctuations in their internal and external conditions. Of course, scientists have paid atten- tion to single cells ever since the fi rst micro- scopes were invented. What’s changed is that researchers are now applying to indi- vidual cells the powerful techniques, includ- ing genome sequencing, mass spectrometry, and gene expression analysis, that formerly required batches of cells. “Real biological tis- sues are complex, and if you want to dissect that complexity and heterogeneity, you have to have tools to do it at the single-cell level,” says biophysicist Stephen Quake of Stanford University in Palo Alto, California. Good technique Single-cell research tools range from old standbys to cutting-edge inventions (see side- bar for a sample of methods). Many of them allow researchers to get into what Quake calls “production mode,” analyzing large num- bers of individual cells in parallel or over a short period of time. The technology he calls
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This note was uploaded on 02/15/2012 for the course BIO 551 taught by Professor Hsai during the Spring '12 term at USC.

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Science-2011-Leslie-The_Power_of_One - NEWSFOCUS Small...

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