Molecular Cloning of Immunoglobulin Heavy Chain Gene Translocations by Long Distance Inverse PCR

B-cell functions as a key player in the humoral immunity producing immunoglobulin protein in mammalian. To produce wide-ranged and antigen-specific antibody, the B-cell undergoes genetic rearrangement of immunoglobulin genes during its maturation process. The genetic rearrangements in immunoglobulin genes require unstable steps for genome; breakage and re-ligation of the double strand DNA. In the unstable steps, misconduct can be occurred; leading chromosome translocations involving immunoglobulin genes. Chromosome translocations involving the immunoglobulin heavy chain (IGH) locus on chromosome 14q32 are found in various B-lymphoid malignancies, including B-cell precursor lymphoblastic leukemia (BCP-ALL), B-cell non-Hodgkin's lymphoma (B-NHL), and myeloma. Chromosome translocations involving IGH locus are often associated to disease entities among the B-lymphoid malignancies; thus, identification of certain translocation is clinically important information for definitive diagnosis. Moreover, molecular cloning of the IGH translocation breakpoint allows the identification of genes of physiologically or pathologically importance in B-cells (Willis and Dyer, 2000; Küppers and Dalla-Favera, 2001; Siebert et. al., 2001). The consequence of IGH translocations is the deregulated expression of the target gene controlled by potent B-cell-specific transcriptional enhancers within the IGH locus, resulting from physically close apposition with the IGH locus. The vast majority of target genes of IGH translocations play a fundamental role in Bcell biology, such as cell growth, differentiation, apoptosis and signal transduction (Wills and Dyer, 2000). Thus, deregulated expression of those genes alters B-cell fate and may initiate malignant transformation of the affected B-cell. To date, many IGH translocation breakpoints have been molecularly cloned and the target genes have been identified; however, several recurrent breakpoints remain to be cloned (Heim and Miltelman, 1995). Molecular cloning of IGH translocation breakpoints would reveal the involvement of either genes of unknown biological functions or the unsuspected oncogenic potential of known genes. Moreover, some target genes of IGH translocation have been found to be deregulated by gene amplification or unknown genetic mechanisms rather than IGH translocation, thereby contributing to disease development or progression (Dyer et. al, 2010).