Molecular cloning of the chromosomal breakpoints from cases LB375 and LB1017. (A) Schematic representation of the cloned breakpoints and their respective germ-line counterparts (chr 14q32 and chr 4p16.3). From the top: a diagram of the 2 Mb cosmid and P1 conting region22 where the HD gene, the cosmid clone L75b9, and the FGFR3 gene23 are located; gaps in the expanded line representing the L75b9 clone indicate the sequencing gaps in the reported sequence22; the germ-line 4p16.3 restriction map, derived from phage clones λTwT and λAB3, and the probes used for Southern and Northern blot analyses (H/H1.8, B/B1, A/B1.3) are shown. The vertical arrows indicate the positions of the breakpoints; for case LB278, the BamHI fragment where the breakpoint is thought to occur is also indicated. Chromosome 14 sequences are indicated by open boxes with black or stippled boxes representing different IGH regions. Chromosome 4 regions are shown as solid lines. Restriction enzyme symbols: B, BamHI; R, EcoRI; H, HindIII; X, XhoI. (B) Nucleotide sequence analysis of the breakpoint regions in cases LB375 and LB1017 and their alignment with the corresponding 4p16.3 and 14q32 germ-line sequences.
