Researchers at the Stanford University School of Medicine have found that human skin cells can be converted directly into functional neurons in a period of four to five weeks with the addition of just four proteins.

The researchers applied a technique to human cells previously used with mice called the “BAM” treatment (for transcription factors called Brn2, Ascl1, and Myt1l). This treatment previously worked well to turn embryonic and induced pluripotent stem (iPS) cells into functional neurons, but the resulting cells were unable to generate the electrical signals that neurons use to communicate with one another.

The researchers found they needed to add a fourth transcription factor called NeuroD.

These skin-cell-derived neurons expressed electrical activity and interacted with mouse neurons grown on a laboratory dish.

The finding is significant because it bypasses the need to first create iPS cells, and may make it much easier to generate patient- or disease-specific neurons for study in a laboratory dish, the researchers said.

The researchers also said it may also circumvent a recently reported potential problem with iPS cells, in which laboratory mice rejected genetically identical iPS cells, most likely on the basis of the proteins used to render them pluripotent.

Marius Wernig, et al., Induction of human neuronal cells by defined transcription factors, Nature, 2011; DOI: 10.1038/nature10202