Infertility affects more people than you might have expected. After a year of timing menstrual cycles, taking steps to boost sperm quality and count, and countless doctor’s visits, about 15 percent of couples still aren’t able to get pregnant. There are treatments, but those don’t always work either, and they sometimes end in multiple pregnancies. A new treatment for infertility may be on the horizon, however, as researchers from the University of Cambridge were able to use stem cells to develop primordial germ cells (PGC), which can eventually develop into either egg or sperm.

“Germ cells are ‘immortal’ in the sense that they provide an enduring link between all generations, carrying genetic information from one generation to the next,” said Dr. Azim Surani, a professor of physiology and reproduction at the university, in a press release.

Primordial germ cells are some of the first cells to be developed when an egg cell is fertilized by a sperm. As the egg divides into a cluster of cells called a blastocyst, some cells remain inside so they can eventually develop into the fetus while others on the outside become the placenta. While most of the inner cells become stem cells, capable of turning into any kind of specialized cell, a small number of them become PGCs, which hold genetic information that will one day be passed down as sperm or egg.

Using human embryonic stem cells and even skin cells, the researchers were able to create these PGCs. But in their research they also discovered something they hadn’t found in mouse studies, for which they had already done these experiments: Humans had a unique gene, called SOX17, that was responsible for determining whether a PGC turned into a sperm or egg cell.

It’s unclear whether SOX17 can be manipulated to change these cells into sperm or egg as a fertility treatment, as more research is needed. Nevertheless, the scientists said the current findings were enough to take the research in various directions, not only with regard to infertility but also cancer and epigenetics — a field of research that investigates the effects of environmental chemicals on our genes’ expressions. In doing so, the researchers may shed light on “age-related disease, which in part might be due to cumulative epigenetic mutations,” Surani said.

Source: Irie N, Weinberger L, Surani A. SOX17 Is a Critical Specifier of Human Primordial Germ Cell Fate. Cell. 2014.