A new chromosomal translocation involves the TCRB and HOXA loci. (A) A TCRB chromosomal translocation was identified in leukemic cells of patient TL43 by dissociation of TCRB-flanking FISH probes. The centromeric Vβ-flanking probe (CTD-3092H9) and the telomeric Cβ-flanking probe (RP11-168I15) were labeled with Texas red and fluorescein isothiocyanate (FITC), respectively. Original magnification, × 63. (B) A 541-bp fragment containing the Dβ1 breakpoint was produced by circled nested PCR (left lane, the rearranged band is shown by an arrow; right lane, molecular weight marker). (C) Breakpoint and flanking sequences of both derivative chromosomes of the TCRB-HOXA translocation TL43. Recognition sequence signal (RSS) heptamer and putative heptamer-like sequence are indicated according to consensus.27 Untemplated nucleotides (N-diversity) are typed in lowercase. GL indicates germline; der, derivative chromosomes. (D) Schematic representation of the TCRB-HOXA translocation TL43, drawn to scale according to data from the IMGT Information System (http://imgt.cines.fr) and the UCSC Genome Bioinformatics site (http://genome.ucsc.edu/), and to the DNA sequences of the breakpoint regions of the 2 derivative chromosomes. Chromosomes are depicted according to the direction of the TCRB and HOXA gene transcription (except for the EVX1 gene, which is transcribed in the opposite direction as indicated by arrow). Breakpoints are indicated with arrows.
