Predictably, the essential genes tend to be involved in fundamental biological processes, like copying DNA, transcribing genes, and building proteins. Perhaps less predictably, Sabatini found that we have no idea what 18 percent of the essential genes on his list are doing—a testament to how much we still have to learn about the most critical parts of ourselves.
The two teams are also trying to discover genes that are essential in specific contexts. Moffat likens this to a daisy: The core represents genes that are always necessary, while the petals represent those that are important, say, when cells are growing or reproducing, or in one type of cell but not another. CRISPR makes it easy to analyze both the core and the petals. “Anything we can detect in a dish, like whether a cell is square or red, we can find the genes that underlie that,” says Sabatini. “And if you’re interested in cancer, you can say: Give me the genes that each type of cancer, and only that type of cancer, cares about.”
Cancer is foremost on his mind. His team has already catalogued the essential genes in four cancer-cell lines, taken from patients with leukemia and lymphoma. Meanwhile, Moffat analyzed cell lines grown from cancers of the brain, colon, skin, and cervix.