Circular RNAs in Hedgehog Signaling Activation and Hedgehog-Mediated Medulloblastoma Tumors

Within the past decade, circular RNAs have largely emerged as novel regulators of human biology, including brain function and cancer development. On the other hand, the Hedgehog pathway has established roles in regulating biological processes, including tumorigenesis. Here, the circular RNA transcriptome, in the context of Hedgehog signaling activation of medulloblastoma Daoy and human embryonic palatal mesenchyme HEPM cells, was determined. In total, 29 out of the 30 selected circular RNAs were validated by Sanger sequencing, with some regulated to a limited extent by Hedgehog signaling. Interestingly, back-spliced junctions, the marker of exonic RNA circles, were also identified at a low frequency within poly (A) mRNAs, reflecting exon repetition events. Thirteen circular RNAs had reduced expression in human medulloblastoma tumors in comparison to normal cerebellum. For seven out of these thirteen RNA circles, the linear mRNAs originating from the same genes did not exhibit a reduced expression. Depletion and/or overexpression of these seven circular RNAs minimally affected medulloblastoma cell proliferation. These findings highlight that differential expression of a gene product may not necessarily elicit an obvious phenotypic impact. Consequently, further analysis is required to determine the possible subtle contributions to the development of this cerebellar tumor.