Julia Joung

Julia Joung, 32, arrived at the Broad Institute, in Cambridge, Massachusetts, and the lab of gene-editing expert Feng Zhang in the early days of the excitement over the gene-editing tool CRISPR. There, Joung dove into “genome-scale screening,” or using tools such as CRISPR to alter each of the 20,000 genes in the human genome—and then watching to see what happens.

Such genetic screening, often carried out on stem cells, is a top priority for data-driven labs seeking to explore biology’s logic from a wide angle. 

In theory, stem cells can be coaxed to develop into any type of cell. In practice, though, many types are hard—even impossible—to generate in the lab.  

Proteins called transcription factors can determine what cells decide to become. But which ones? There are more than 1,500 factors in our bodies.

Initially, Joung found a single factor that would turn stem cells into nervous system cells. But her research evolved into a larger project. Why not add every single transcription factor to stem cells and measure the effect each factor had on how those cells behaved?

The result of her survey, published in January, is an “atlas” of how individual transcription factors affect the identity of stem cells. The ultimate goal, she says, “is to be able to make any cell type, and in a very controlled way.”

Supplies of specific cells could be useful for testing drugs or new types of therapies. Other scientists studying transcription factors hope to find combinations that will form human eggs in the lab or even provide the key to rejuvenation treatments. “We aren’t just generating lists when we screen. It’s a list with a purpose,” says Joung. “There’s always that end goal.”