The t(4;14) translocation and IgH-MMSET hybrid RT-PCR assays.

(A) Schematic representation of areas of interest from 4p16 and 14q32. Genomic distances of 4p16 are to relative scale, as determined by genomic contig NT_022865.9. Any distance smaller than 1 kb is not indicated. The directions of transcription for TACC3, FGFR3, and LETM1 are indicated by horizontal arrows; for MMSET this also indicates the location of the start codon. MMSET exons 2a, b, c, and d are indicated by A, B, C, and D. The approximate t(4;14) breakpoint locations on chromosome 4 of the MM cell lines KMS-11 (MB4-1), NCI-H929 (MB4-2), JIM3, and OPM2 (MB4-3) are represented by vertical arrows. The breakpoint regions MB4-1, MB4-2, and MB4-3 on 4p16 are represented by marker bars. A representation of der(4) and der(14), created by an MB4-1 translocation with a chromosome 4 breakpoint between MMSET exon 1 and exon 2a, is shown. (B) Representative hybrid transcripts created on der(4) and der(14) by the different breakpoint transcripts and the relative binding locations of PCR primers. Primers are indicated by horizontal arrows. Two different diagrams are shown for MB4-1 to highlight the expected differences in the der(14) reactions, depending on the breakpoint location relative to MMSET exon 1. (C) Sensitivity of the single-stage J_H-ms6r assay determined by mixing MB4-2 type t(4;14)⁺ cell line NCI-H929 with t(4;14)⁻ cell line U266 is 1 of 50 positive cells. Numbers above each lane represent the dilution of t(4;14)⁺ cells. (D) The sensitivity of single-stage Iμ1-ms6r assay is 1 of 50 positive cells. (E) Sensitivity of the nested 2-stage assay is 1 of 10 000 positive cells.