Fig. 4

Gene copy number changes on chromosome 7 detected by ddPCR-based copy number analysis in 10 control blood samples and 20 tumor samples, previously shown to have a chromosome 7 gain (tumor samples 1–13) or a balanced chromosome 7 status (tumor samples 14–20). The threshold for a copy number gain at an individual genomic locus was set to ≥ 2.5 according to Crespo et al. [43]. Tumor samples 1–15, glioblastoma IDH-wildtype, CNS WHO grade 4; Tumor sample 16, astrocytoma, IDH-mutated, CNS WHO grade 4; Tumor samples 17–18, diffuse midline glioma, H3 K27-altered; Tumor sample 19, pilocytic astrocytoma, CNS WHO grade 1; Tumor sample 20, others (atypical teratoid/rhabdoid tumor). White rectangles, copy number value < 2.5; light grey rectangles, copy number value ≥ 2.5 and < 5.0 (low-level copy number gain); black rectangles, copy number value ≥ 5.0 (high-level copy number gain/gene amplification); crossed rectangle, data not available. None of the control blood samples displayed evidence of gains of whole chromosome 7 indicative of trisomy 7. The results obtained by ddPCR for chromosome 7 gain by ddPCR were independently validated by other methods. Note that individual tumors demonstrated evidence for focal high-level copy number changes on the background of whole chromosome 7 gain