Fig. 1.

Characterization of circMMP9 in human GBM. a Clustered heat map showing tissue-specific circRNAs (top 20 upregulated and downregulated circRNAs), which are displayed on a scale from green (low) to red (high), between three human GBM tissues and adjacent normal tissues. The arrow represents the circRNA (hsa_circ_001162) with the greatest differential expression. b Detailed information for the top 20 upregulated and downregulated circRNAs according to the extent. c Schematic representation of circMMP9 formation. The splice junction sequence was Sanger sequenced, and the RNAs were detected via PCR. Divergent primers could produce circRNAs in cDNA but not in genomic DNA (gDNA); convergent primers could produce cDNA and gDNA. d The expression level of circMMP9 was detected by qRT-PCR in GBM tissues and adjacent normal brain tissues (n = 18, P < 0.05); GAPDH served as the internal control. e-f circMMP9 expression was measured using in situ hybridization (FISH) in GBM tissues and adjacent normal brain tissues (n = 18, P < 0.05). g-h Confocal FISH was performed to determine the location of circMMP9 in U87 and U251 cells