PMC8629764_01
Karyotype. 46,XY,t(5;7;7) (q33.2; q32; q11.2). Arrows indicate the direction of the transfer of chromosomal material between the derivative chromosomes 5, 7 and 7.
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Cytogenetic analysis showed a 3-way translocation involving chromosome 5 and both chromosomes 7 with breakpoints at 5q33.2, 7q32 and 7q11.2 [(46, XY,t(5;7;7)(q33.2;q32;q11.2)] as the only abnormality (Figure 1).
Metaphase FISH using break apart probes for 3'PDGFRB (red signal) and 5'PDGFRB (green signal). Arrow A shows the normal chromosome 5 with an intact PDGFRB fusion signal (yellow). Arrow B shows the derivative chromosome 5 containing only the 3' portion of PDGFRB (red signal). Arrow C shows the derivative chromosome 7 with the translocated 5' portion of PDGFRB (green signal).
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FISH with PDGFRB and with whole chromosome painting probes to chromosomes 5 and 7 confirmed the 3-way translocation and showed that sequences 5' to PDGFRB were translocated to the derivative chromosome 7 with the 7q32 breakpoint (Figure 2). For other PDGFRB fusions, the critical oncogenic fusion is on the derivative chromosome 5, which retains the 3' portion of PDGFRB (Figure 3).
Whole chromosome 5 paint with green fluorescent probes. Arrow A shows the normal chromosome 5 with fluorescence label seen throughout the chromosome indicating intact chromosomal material. Arrow B shows the derivative chromosome 5; the unlabeled end of the long arm indicates the translocated chromosomal material from the derivative chromosome 7. Arrow C shows the derivative chromosome 7 containing translocated material from the der(5).
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FISH with PDGFRB and with whole chromosome painting probes to chromosomes 5 and 7 confirmed the 3-way translocation and showed that sequences 5' to PDGFRB were translocated to the derivative chromosome 7 with the 7q32 breakpoint (Figure 2). For other PDGFRB fusions, the critical oncogenic fusion is on the derivative chromosome 5, which retains the 3' portion of PDGFRB (Figure 3).
Whole chromosome 7 paint with red fluorescent probes. Arrow A shows the derivative chromosome 7. Arrow B shows the derivative chromosome 7 with the unlabeled part at the end indicating the translocated chromosomal material from the derivative chromosome 5. Arrow C shows the der(5) with translocated chromosomal material from der(7).
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Thus, the partner gene for this unidentified PDGFRB rearrangement appeared to lie at the 7q11.2 breakpoint (Figure 4).