Recurrent chromosome 16 translocations. (A) SKY/FISH analyses of Igλ translocations in CXP lymphomas. (A, top) schematic map of Igλ locus in germline configuration and the location of the three BACs used for FISH (P9, E14, and P12).(bottom) SKY revealed a t(12;16) translocation in CXP68, and a reciprocal t(16;15) and t(15;16) translocation in CXP62. FISH and chromosome paints (Chr12 pink, Chr16 light blue or white, Chr15 green) showed the breakpoints of Chr16 translocations occurred in different regions of the Igλ locus, indicated by yellow lightning symbols over metaphases hybridized with different Igλ BACs. 3′ IgH (pink) and P9 (light blue) BACs were colocalized at the junction of t(12;16) in CXP68. CXP62 has a reciprocal translocation with P12 BAC (white) on the der(16)t(16;15) and E14 and P9 (white) BACs on the der(15)t(15;16). At least 15 metaphase spreads were analyzed for each of the cytogenetic analyses, and representative clonal translocations observed in >80% of the metaphases are shown. (B, top) Cloning of t(12;16) breakpoints from a genomic library made from CXP68 DNA. Nucleotide sequence analyses of cloned junction (shown in Fig. S7 B) indicated breakpoints occurred between Cδ in IgH and Jλ2 in Igλ locus. (bottom) Cloning of t(16; 15) breakpoints from a genomic library made from CXP62 DNA. Nucleotide sequence analyses indicated breakpoints occurred between sequences upstream of c-myc exon 1 and Jλ1 with 3′ Igλ enhancer in close proximity. At least two independent phage clones were isolated from each genomic library and the junctions found in phage clones were independently confirmed as clonal junctions in a given tumor by PCR analyses of tumor DNA sample. Fig. S7 is available.