Problem

To truly understand the human genome, we need better insight into how individual cells differ. While every cell in a person’s body has basically the same DNA blueprint, there’s great variation in the way that genetic information is actually acted on, or expressed, at any given time. It’s the reason one cell becomes a neuron that plays a role in memory, while another cell becomes part of a person’s toenail. Even a given organ, like the brain, encompasses different types of cells, and individual cell types, too, have variations. Inadequate knowledge about how genes are expressed in different cells is greatly hampering progress in genomic medicine.

Solution

Evan Macosko has helped invent a technology called Drop-Seq, which allows a researcher to look at thousands of cells, one by one, to determine how each is carrying out its genetic instructions. Such analysis of a single cell can be done with existing tools, but it is typically painstaking, expensive work that involves dropping individual cells into tiny wells. “If you get two cells in a well, you’re screwed,” says Macosko.

To greatly speed up the process, Macosko figured out how to take each cell he wanted to analyze, break it apart, and attach the expressed genes to a tiny bar-coded bead. Once material from each cell is labeled, the genes can be analyzed rapidly—all for a cost of just seven cents a cell.

Macosko says he and his team have nearly finished profiling hundreds of thousands of cells spanning most of the mouse brain. Next stop: the 86 billion neurons and innumerable other cells that make up the human brain. By analyzing the great variation in the cells in our brains, he hopes to identify the rogue cells that are malfunctioning or interfering with normal function in disorders like schizophrenia, autism, and Alzheimer’s.

—Michael Reilly