A team of scientists has uncovered details of the particular cellular mechanisms that control the direct programming associated with stem cells into motor neurons. The scientists examined changes that occur in the cells over the course of the reprogramming process. They discovered a dynamic, multi-step process by which multiple independent changes eventually converge to change the originate cells into motor neurons.
“There is a lot of interest in generating motor neurons to analyze basic developmental processes as well as human diseases like WIE and spinal muscular atrophy, ” said Shaun Mahony, assistant professor of biochemistry and molecular biology in Penn State and one of the lead authors of the papers. “By detailing the mechanisms underlying the direct programing of motor neurons from stem cells, our research not only informs the study of motor neuron development and it is associated diseases, but also informs our understanding of the immediate programming process and may help with the development of techniques to generate additional cell types. ”
The direct development technique could eventually be used to regenerate missing or even damaged cells by converting other cell types to the missing one. The research findings, which appear online within the journal Cell Stem Cell on December 8, 2016, show the challenges facing current cell-replacement technology, however they also outline a potential pathway to the creation of a lot more viable methods.
“Despite having a great restorative potential, direct programming is generally inefficient and doesn’t completely take into account molecular complexity, ” said Esteban Mazzoni, a good assistant professor in New York University’s Department of The field of biology and one of the lead authors of the study. “However, the findings point to possible new avenues for enhanced gene-therapy methods. ”
The researchers had demonstrated previously that they can transform mouse embryonic stem cells directly into motor neurons by expressing three transcription factors — genes that control the expression of other genetics — in the stem cells. The transformation takes regarding two days. In order to better understand the cellular and genetic systems responsible for the transformation, the researchers analyzed how the transcribing factors bound to the genome, changes in gene appearance, and modifications to chromatin at 6-hour intervals throughout the transformation. “We have a very efficient system in which we can change stem cells into motor neurons with something like the 90 to 95 percent success rate by adding the cocktail associated with transcription factors, ” said Mahony. “Because of that effectiveness, we were able to use our system to tease out the facts of what actually happens in the cell during this alteration. ”
“A cell in an embryo grows by passing through several intermediate stages, ” observed Uwe Ohler, senior researcher at the Max Delbrü ck Center for Molecular Medicine (MDC) in Berlin and something of the lead authors of the work. “But in immediate programming we don’t have that: we replace the gene transcription network of the cell with a completely new one at the same time, without the progression through intermediate stages. We asked, do you know the timing and kinetics of chromatin changes and transcribing events that directly lead to the final cell fate? inch
The research team found surprising complexity — programming of these stem cells into neurons is the consequence of two independent transcriptional processes that eventually converge. In early stages in the process, two of the transcription factors — Isl1 plus Lhx3 — work in tandem, binding to the genome plus beginning a cascade of events including changes in order to chromatin structure and gene expression in the cells. The 3rd transcription factor, Ngn2, acts independently making additional modifications to gene expression. Later in the transformation process, Isl1 and Lhx3 rely on changes in the cell initiated by Ngn2 to help complete the transformation. In order for direct programming in order to successfully achieve cellular conversion, it must coordinate the game of the two processes.
“Many have found immediate programming to be a potentially attractive method as it can be performed possibly in vitro — outside of a living organism — or even in vivo — inside the body and, importantly, on the site of cellular damage, ” said Mazzoni. “However, questions remain about its viability to repair cells — especially given the complex nature of the biological procedure. Looking ahead, we think it’s reasonable to use this recently gained knowledge to, for instance, manipulate cells in the spinal-cord to replace the neurons required for voluntary movement that are ruined by afflictions such as ALS. ”
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