PCR amplification of WM and IgM MGUS VDJ-S regions reveals rare deletion events. (A) CDR2/SwA and CDR2/Sw15as fragments analyzed by agarose gel electrophoresis reveal multiple VDJ-S fragments in patient WM1-01 (lane 13). Arrow indicates the deleted switch region of WM1-01 clone. Lanes 1-3, IgM MGUS clones using V_H3/J_H4 gene segments; lanes 4-9, WM clones using V_H3/J_H4 gene segments; lane 10, WM clone using V_H3/J_H3 gene segments; lanes 11-13, WM clones using V_H3/J_H6 gene segments; M indicates marker. Expected sizes of CDR2/SwA fragments are 7.8 (lanes 1-9), 8.1 (lane 10), and 6.8 kb (lanes 11-13). Expected sizes of CDR2/Sw15as fragments are 4 (lanes 1-9), 4.3 (lane 10), and 3 kb (lanes 11-13). (B) Deletions in subcloned WM1-01 VDJ-S fragments. The expected germline configuration is presented at the top, with subcloned fragments indicated by bars. VDJ refers to rearranged variable, diversity, and joining gene segments.