Genetic Engineering & Biotechnology News

DEC 2018

Genetic Engineering & Biotechnology News (GEN) is the world's most widely read biotech publication. It provides the R&D community with critical information on the tools, technologies, and trends that drive the biotech industry.

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12 | DECEMBER 2018 | Genetic Engineering & Biotechnology News | Part of the problem is that miRNA molecules consist of nucleotide sequences that are so short they pose challenges with respect to probe design and label selection. Different miRNAs may have widely varying melting temperatures for annealing reactions, they may be present in concentrations that vary by orders of magnitude, and they may be hard to distinguish from miRNA precursors and variants aris- ing from post-transcriptional modifications. Consequently, identifying and quantifying miRNA molecules is inherently challenging, even though they are relatively stable compared to messenger RNA (mRNA) molecules. Another part of the problem is that miRNAs are found in different contexts—in tissues, in isolated cells, in extracellu- lar vesicles, and bound with proteins while swimming in bio- fluids. Different miRNA sample types call for different kinds of extraction techniques, and even extraction techniques of the same kind may vary in small but ultimately significant ways, leading to divergent results. Other sources of variabil- ity include miRNA measurement and data interpretation. To overcome variability, and thus find much desired com- mon ground, researchers and tool providers alike are work- ing hard to standardize miRNA profiling protocols, recon- cile findings from disparate research teams, and develop applications that deliver reliable diagnostic and prognostic findings. As they advance their work, researchers and tool providers fulfill, step by step, the potential for miRNA bio- markers that has been demonstrated in many recent studies. MicroRNAs as Biomarkers Many studies have shown how miRNA profiles may differ depending on health status. This point is easily con- firmed. All the reader need do is open a search engine and plug in a few key terms: miRNA, biomarker, review, and cancer—or another condition, such as cardiovascular dis- ease or neurodegenerative disease. Besides looking back, readers may survey current re- ports on miRNA biomarker research. For example, this past year, new findings have been announced for the fol- lowing conditions: • Bronchopulmonary dysplasia, a disease that can lead to death or long-term disease in low-birth-weight infants (University of Alabama at Birmingham, JCI Insight). • Atrial fibrillation, an irregular heart rhythm often overlooked because of a lack of symptoms (Tokyo Medical and Dental University, Circulation). • Lou Gehrig's disease, or amyotrophic lateral sclerosis (ALS), a neurodegenerative disease that destroys nerve cells and causes permanent disability (Tel Aviv University, The Journal of Neuroscience). • Cognitive performance deficits related to sleep deprivation. (University of Pennsylvania School of Medicine, SLEEP 2018). • Alzheimer's disease (Indiana University, Nature Scientific Reports). • Sepsis, an extreme and life-threatening reaction to infec- tion that can trigger inflammation throughout the body (Columbia University Irving Medical Center, Nature). • Blood doping, the transfusion of autologous red blood cells to enhance athletic performance (Duke University, British Journal of Haematology). MicroRNA Proling Essentials MicroRNAs, noncoding RNAs that are about 22 nucleo- tides long, regulate gene expression by binding to mRNAs, inhibiting their translation or resulting in their degradation. Although miRNAs are not especially numerous—only about 1000 are thought to be derived from the human genome— each miRNA may regulate hundreds of mRNAs. Conse- quently, miRNAs participate in many biological processes, including cell differentiation, proliferation, and apoptosis. When miRNA expression goes awry, the consequences may include the dysregulation of gene expression, which in turn may result in disease. Fortunately, miRNAs are relative- ly stable in various sample types—in liquid biopsy samples as well as fresh and fixed tissue samples—raising the pos- sibility that miRNAs can be sufficiently well quantitated to disease signatures to be recognized. MicroRNA quantitation and profiling essentials may be studied from many sources, including a magisterial article that appeared in Nature Reviews Genetics. This article was pre- pared by a team of researchers based at the Fred Hutchinson Cancer Research Center and led by Muneesh Tewari, M.D., Ph.D., who is currently a professor of internal medicine and biomedical engineering at the University of Michigan. The article outlined miRNA profiling workflows for dif- ferent sample types, emphasized the importance of qual- ity control, and summarized the main miRNA quantitation techniques. The workflows encompassed: • Purification techniques (such as gel electrophoresis, immunoprecipitation, and laser capture microdissection). • Quality control checks (such as measuring spike-in oligo concentrations or housekeeping RNA expression, spectrophotometric analysis, or automated capillary electrophoresis). • MicroRNA measurement techniques (such as quantitative reverse transcription PCR-based methods, hybridization-based methods, and RNA sequencing). OMICS According to a recent study led by the University of Michigan's Muneesh Tewari, M.D., Ph.D., RNA-sequencing library preparation methods may inconsistently quantitate microRNAs. The study, which evaluated results provided by nine laboratories, described library preparation methods that can reduce protocol- and sequence-speci•c biases, thereby improving the accuracy and comparability of sequencing experiments. Sigrid Knemeyer, SciStories MicroRNA Prolers Cite Reconcilable Dierences In microRNA (miRNA) profiling, researchers confront a good news / bad news scenario. The good news is: miRNA profiles show promise in biomarker discovery. The bad news is: miRNA profiles generated by different research teams don't always overlap—at least not so much as to inspire confidence that researchers are converging on clinically useful assays.

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