In an exciting paper by from a group from Stanford, researcher Andrew Yoo and colleagues have demonstrated that fibroblasts can be transformed into neurons using RNAi to coax these skin cells into becoming functional neurons.

Different cell type (skin cells, neurons, osteoblasts, etc.) start out from less specialized cells, called stem cells. What a cell will become (its characteristics and functions) is also known as the cell’s “fate.” It may seem odd that seemingly simple skin cells can be transformed into cells that make up the thinking brain. However, all cells have a common set of DNA instructions, and it is the collection of instructions that are being actively “read” that determine what fate a cell well adopt.

In this study, two microRNAs (miR-9/9* and miR-124) were introduced into the fibroblasts. These micro RNAs then go on to alter the expression of their target genes. While RNAi can have very specific effects when there is only one target gene, in this case the micro RNAs targeted a set of genes that had global effects on which set of DNA instructions were being carried out by the cell through a process called chromatin remodeling.

Chromatin (the proteins involved in packaging DNA) determines which genes can be read by the cell, and which genes are hidden (unreadable) by the cells. Since microRNAs miR-9/9* and miR-124 act on a system of proteins (the SWI/SNF-like BAF chromatin remodeling complex) these 2 microRNAs have a greatly amplified effect on many sets of genes that are neuron specific.

Unlike other cell types which are easily collected, neuronal cells (especially in specific clinically relevant contexts) are hard to come by. Being able to create neuronal cells in a “one step” process (vs. previous research methods which could transform skin cells to neuronal cells via an intermediate stem cell step) is an advance that has great potential to speed up neuroscience research.