Graphic representation of the 3 breakpoints in case No. 7.

(A) The 3′Sμ aberrant fragment was amplified by long-distance inverse PCR. Genomic DNA from case No. 7 was digested with EcoRI, was self-ligated, and long-distance inverse PCR was performed using 4 primers (3MFA, 3MRA, 3MFB, 3MRB) internal to the 3′Sμ region. The 3 breakpoints are generated by a deletion from downstream JH6 to the middle of the Sμ region and by an insertion of a chromosome 15 gene (KIAA0307) into the Sμ region. Eμ = intronic enhancer, Sμ = switch μ region, Cμ = constant μ exons, M1, M2 = exons for membrane form. (B) Alignment of the breakpoint regions of case No. 7 with germline GenBank sequences. Numbers indicate the nucleotide position at which the breakpoint occurred within the corresponding GenBank sequence. These sequences are available from GenBank under accession numbers AF156 533, AF156 534, and AF156 535. HSIMMDL = GenBank DNA sequence of the human immunoglobulin D segment locus, HSJHCMU = GenBank nucleotide sequence of the IgH Sμ region, AB002 305 = GenBank nucleotide sequence of human mRNA for KIAA0307 gene.