An Update on Reprogramming Glial Cells into Neurons

Neuroglia are a variety of of types of support cell in the brain and nervous system. They perform all sorts of necessary tasks, some of which are still being uncovered, such as the recent discovery that recycling of damaged mitochondria in long axons is delegated to astrocyte glial cells rather than being performed by the nerve cell owning the axon. One of the possibilities opened up by the growing ability to reprogram cell state is to change some of these supporting glial cells into functional neurons, thus creating an increased supply of new cells to repair brain injuries and the damage of aging. Some inroads have already been made in animal studies, and basic proof of concept work has demonstrated that this is a potentially practical approach. Here is a more recent update:

The portion of the adult brain responsible for complex thought, known as the cerebral cortex, lacks the ability to replace neurons that die as a result of Alzheimer's disease, stroke, and other devastating diseases. A [study] shows that a Sox2 protein, alone or in combination with another protein, Ascl1, can cause nonneuronal cells, called NG2 glia, to turn into neurons in the injured cerebral cortex of adult mice. The findings reveal that NG2 glia represent a promising target for neuronal cell replacement strategies to treat traumatic brain injury.

[Researchers] have previously shown that Sox2, Ascl1, and other transcription factors - proteins that bind to specific DNA sequences to control the activity of genes - can induce the nonneuronal "support cells" known as glia to turn into neurons. It has been difficult, however, to convert glia into neurons after brain injuries such as stroke in the adult cerebral cortex of living animals. To test potential brain repair strategies, [the researchers] delivered transcription factors into the cerebral cortex of adult mice three days after traumatic injury. Surprisingly, they found that Sox2 alone or in combination with Ascl1 was sufficient to trigger the emergence of neurons, contrary to the widely accepted view that Sox2 prevents stem cells from turning into more mature cells such as neurons. Notably, the majority of cells that converted into neurons were NG2 glia. These glial cells have received relatively little attention in the past, even though they represent a promising cellular source for brain repair strategies because of their abundance and life-long capacity for proliferation.

Link: http://www.sciencedaily.com/releases/2014/11/141120123136.htm

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