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.

The neurons fire pulses with periods of rest in between. This is commonly seen in sleeping adults. These pulses were seen between neurons located in the cerebral cortex. The cerebral cortex is involved in sensory information, thinking, emotion and consciousness. Even when they are not receiving input, the neurons will continue the pattern of firing and resting. When we sleep, our neurons will fire and rest as a way of reminding the rest of the brain that even though those cells are no longer working, they’re still alive! It’s as if the neurons are reminding the rest of the brain that they’re still there. Because this is seen in adults and in fetuses, this suggests that this alternative firing and resting activity is a very basic feature of the brain that starts occurring in very early developmental stages.

But now why are they firing so early in life? A mouse’s neurons will fire in synchronized waves. This plays a role in wiring the nervous system during development in order to link the neurons to corresponding body parts. Could this be the same for the human brain? Researchers are unsure if the developing neurons in lab dishes are in synch. If they are, the firing could be part of a mapping process during development.

Using this research, researchers might be able to soon look into what the result is when these neurons don’t form in the right places. The wrong positions might result in numerous disorders. Autism Spectrum disorders may also be related to improper firing.