While chimeric RNAs may be generated by transcription-mediated mechanisms such as "trans-splicing" and "read-through/splicing" (Zhang et al., Cancer Discov 2:598-607, 2012; Zaphiropoulos, Front Genet 2:92, 2011; Li et al., Cell Cycle 8:218-222, 2009; Jividen and Li, Genes Chromosomes Cancer 53:963-971, 2014; Jia et al., Trends Cancer 2:475-484, 2016), most highly expressed chimeric RNA species identified so far are usually transcribed directly from fusion genes. Fusion genes, formed by joining two parental genes as a result of chromosomal rearrangements, are hallmarks of many types of cancer. Various methods can be deployed for confirming a particular fusion gene as the original source of transcribed chimeric RNA. In this chapter, we discuss commonly used methodologies such as genomic DNA breakpoint mapping and fluorescent in situ hybridization useful for confirming gene fusion events. In addition, we highlight the development of new technologies such as de novo whole-genome optical mapping suitable for global analysis of genomic arrangements. The advantages and disadvantages of each of these technologies are presented and compared.
Keywords: Bionano; Chimeric RNA; Fluorescent in situ hybridization (FISH); Fusion gene; Genomic DNA PCR; Genomic breakpoint; Next generation mapping (NGM).