Traditionally, chimeric RNAs were considered to be exclusive to cancer cells. When occasionally observed in normal samples, they were usually considered to be transcriptional 'noises,' or artifacts due to template switching during the reverse transcription and/or Polymerase chain reaction (PCR) steps of experimentation. However, with the advances being made in next generation sequencing technologies and software tools, as well as the accumulation of new experimental evidences, increasing numbers of chimeric transcripts are being identified in noncancerous tissues and cells. Recent studies have also demonstrated functional relevance, for at least a subset of chimeric RNAs in normal physiology. The advances have resulted in an influx of knowledge; this knowledge indicates that chimeric RNAs are a component of basic biology, and thus challenging traditional dogma. In addition to chromosomal rearrangement, chimeric RNAs can also be formed via different molecular mechanisms including cis-splicing of adjacent genes (cis-SAGe) and trans-splicing, as well as others. Little is known about the details of these noncanonical splicing processes. However, research in this new field promises to not only advance our basic understanding of the human genome and gene regulation, but also lead to improvements in clinical practice, especially in the areas of cancer diagnostics and treatment. WIREs RNA 2017, 8:e1427. doi: 10.1002/wrna.1427 For further resources related to this article, please visit the WIREs website.
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