E2A, 19p13.3, Green
PBX1, 1q23.3, Red
HLF, 17q22, Blue
The E2A probe, labelled in green, contains two probes (110kb and 146kb) that cover the 3’ end of the E2A (TCF3) gene and flanking region and a 321kb probe that covers a region 5’ (centromeric) to the gene. The PBX1 probe, labelled in red, contains two probes (147kb and 110kb) that map within the PBX1 gene and a 117kb probe that maps 3’ (telomeric) to the gene. The HLF probe, labelled in blue, consists of a 482kb probe 5’ (centromeric) to HLF and two probes (323kb and 166kb) that are 3’ of the gene.
The TCF3 (transcription factor 3) gene is located at 19p13.3, PBX1 (pre-B-cell leukemia homeobox 1) gene is located at 1q23.3 and HLF (hepatic leukemia factor) at 17q22.
Translocations involving TCF3 are some of the most common rearrangements in childhood B-cell acute lymphoblastic leukaemia (ALL)1,2.
PBX1 and HLF become fused to TCF3 as a result of the t(1;19)(q23;p13) and t(17;19)(q22;p13) translocations, forming the TCF3-PBX1 and TCF3-HLF fusion genes, respectively. A rare cryptic inversion, inv(19)(p13;q13), has been reported to fuse TCF3 to TFPT (TCF3[E2A] fusion partner [in childhood leukaemia]), resulting in the TCF3-TFPT fusion gene1.
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