“These genes inside me are expressing a specific disease!” is a phrase that is more and more likely to be used by patients in the near future. The study of gene expression is proving to be a powerful tool for the understanding of causes and treatments of various human conditions including cancer and viral infections such as Ebola and Zika.1 RNA is considered to be the precursor of life. It mediates the essential role of carrying instructions from DNA for the synthesis of proteins, and is the only genetic material of various viruses. It therefore comes as no surprise that the analysis of RNA species inside the human body can be exploited to yield useful insights about its overall health status. Unlike DNA, RNA is a highly dynamic and diverse molecule, giving us a window on how the expression of genes is continually changing. Therefore, RNA sequencing can not only provide a measure of how active a specific gene is, it can also detect the presence of new and altered RNA species.
For example, RNA sequencing can detect the presence of new RNA molecules arising from the fusion of two genes, which occurs in a number of cancers. Not only does this enable the diagnosis of myeloid leukemia, response to treatment can also be followed by measuring the expression of another gene fusion.2,3 Further research has found that variants of the same RNA molecule are implicated in developmental disorders, neurodegenerative disorders, and cancers.4-7 The presence of extracellular RNA in bio-fluids can also be used as an indication of organ or tissue injury, such as in cancer metastases, and foetal health.1,8 One of the great benefits of this technology is that it’s a non-invasive indicator of disease, since only blood samples are needed as opposed to, for example, tumour biopsies. As blood samples can be taken frequently, patients can have their gene expression monitored over time and their treatment adjusted as necessary. Finally, RNA sequencing unlocks the potential to measure regulatory RNA species responsive to change, and detect the presence of foreign RNA molecules such as pathogenic viral RNA.1
RNA sequencing is having an ever-increasing impact on clinical practice. The current focus is the development of RNA sequencing technology with lower error rates and from individual cells to avoid sample variability.9 RNA is therefore a strong front-runner to be a powerful future biomarker for the diagnosis of cancers and diseases; a constantly varying RNA pool to complement the analysis of relatively unchanging DNA.
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