British scientists have discovered a genetic mechanism in the development of the nervous system that they say might one day be part of new treatments for stroke, Alzheimer's disease or brain tumors.

In a study in the journal Nature Neuroscience, the scientists found that a gene, named Sox9, is key to the development of neural stem cells in the human embryo – master cells that in turn develop into brain or spinal tissue.

In experiments in mice, they found that by using the gene they could kick-start the development of these cells, raising the prospect of one day being able to replace or regenerate damaged brain cells in humans.

"With the knowledge that the gene Sox9 plays a central role in the development of our nervous system, we are one step closer to being able to control stem cells in the brain and regenerate different kinds of nerve cells," said James Briscoe from Britain's Medical Research Council, who led the study.

"Being able to correct damaged nerve cells would be a huge leap forward for the millions of people with Alzheimer's, stem cell-related brain tumors or who have suffered from a stroke," he said in a statement, although it is likely to be many more years before such treatments for humans are developed.

Human embryos begin to develop their nervous systems just after two weeks from conception, the researchers explained.

From this stage until about five weeks, the nervous system is largely made up of so-called neuroepithelial cells, which grow rapidly and lay the foundations for brains and spinal cord.
It is only after this stage that the various types of nerves and supporting cells that make up the central nervous system begin to appear. These come from stem cells.

In their study, Briscoe's team found that Sox9 is needed for the neuroepithelial cells to turn into these stem cells.

It also continues to be needed to allow stem cells in the adult brain to retain their properties, such as the ability to self-renew and differentiate.

The scientists also found that a gene known as Shh is needed for Sox9 to work.

By artificially adding Sox9 or Shh to neuroepithelial cells in mouse embryos, they found they were able to kick-start the process of converting them into neural stem cells.

They also found that if there was a genetic defect in Sox9, it was much harder for the mice in their experiments to be able to renew damaged nerve cells later on.

The potential of different kinds of stem cells is being examined by experts around the world for many diseases. But the technology is controversial, in part because some stem cell lines are derived from embryos or fetuses.