Researchers at the Washington University School of Medicine in St. Louis have recently developed a novel method of converting adult human skin cells into medium spiny neurons, a specific category of brain cells that are responsible for controlling movement. Dr. Andrew S. Yoo, Assistant Professor of Developmental Biology, and his research team focused their efforts into designing a protocol that utilized and expanded their existing knowledge of the chemical properties of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
The researchers exposed a sample of skin cells to two small molecules of RNA (or microRNAs), miR-9 and miR-124, because they knew from past experiments that these microRNAs could alter the skin cells’ genetic codes. More specifically, these microRNAs have the potential to rewrite DNA, which would enable the development and expression of different genes. Thereby, a skin cell could function as a medium spiny neuron with the appropriate DNA sequences typically found in medium spiny neurons. Operating under this rationale, the researchers further exposed their sample of skin cells to molecules known as transcription factors that are present in certain areas of the brain where medium spiny neurons exist. Matheus B. Victor, a co-collaborator, explains that, “the transcription factors … then guide the skin cells to become a specific subtype, in this case neurons.”
Dr. Yoo reflects that “the microRNAs, but not the transcription factors, are important components for the general reprogramming of human skin cells directly to neurons”. After injecting the reprogrammed cells into the brains of mice, his team observed that the cells not only survived for at least six months but also behaved similarly to the brains’ native medium spiny neurons. These results have positive implications for future therapies, namely those to treat Huntington’s disease, which is an inherited genetic disorder that causes involuntary muscle movements usually occurring in mid-adulthood.Washington University in St. Louis. "Human skin cells reprogrammed directly into brain cells." ScienceDaily. ScienceDaily, 22 October 2014.
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