Translocation t(12;16) (q13;p11) is found in approximately 95 % of myxoid liposarcomas.
It leads to a joining of the genes TLS (FUS) on the chromosome 16 (exone/introne structure homologous with EWS) with the gene CHOP (DDIT3, GADD153) from the chromosome 12. The points of break are relatively variable. Breakages are most often found in introns 5, 7 and 8 of the gene TLS and in the introne 1 of the gene CHOP. Various types of joinings then give rise to the various types of gene fusions (Type 1 – 4). The fusion gene encodes a chimeric protein, where N-terminal region of the TLS gene with activating domain is fused with the complete gene CHOP, the transcription factor from bZIP family.
Note. part of the myxoid liposarcomas carry the translocation t(12;22) (q13;q12) EWS/CHOP.
The presence of translocation t(12;16), or the CHOP gene breakage is analyzed using RT-PCR and FISH.
When RT-PRC, we isolate mRNA and after its transcription into cDNA we detect chimeric transcripts using PCR. PCR products are vizualized through agarose gel electrophoresis (fig. 1). (Because of the size of the PCR product type 1 (379 bp) it is necessary to perform the analysis from fresh material)
When FISH, we detect the break of the gene CHOP using CHOP Dual Color, Break Apart Rearrangement Probe, Vysis/Abbot (this probe does not identify the specific translocation partner). In a sample positive for rearrangement of the gene CHOP we observe one yellow, one red and one green signal (fig. 2A). In a negative sample we observe two yellow signals (fig. 2B). (dual color filter)
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