A novel approach to clonality analysis. Alterations in genomic methylation of Epstein-Barr virus transformed lymphocytes.

We have studied eight different Epstein-Barr virus transformed cell lines (EBV-LCL) with respect to genomic methylation at a single locus, M-bcr (the major breakpoint cluster region of chronic myelogenous leukemia). Restriction digests with the methylation sensitive enzyme, Hpall, illustrated marked differences in M-bcr methylation patterns between the various cell lines. Some of the cell lines displayed prominent allelic heterogeneity: within each of these samples there were numerous different M-bcr/Hpall allelic fragments on Southern analysis. Other cell lines displayed allelic predominance: within each of these samples a limited number of M-bcr/Hpall allelic fragments predominated. Analysis of Immunoglobulin JH rearrangements demonstrated a close correlation between clonal complexity (i.e. the number of rearranged JH fragments) and allelic heterogeneity of M-bcr methylation (i.e. the number of M-bcr/Hpall fragments). We conclude that analysis of genomic methylation in the M-bcr locus may offer a novel approach to clonality determination in EBV transformed lymphocytes.