Chromosome 7 long arm deletion breakpoints in preleukemia: mapping by pulsed field gel electrophoresis.

Chromosome 7 long arm deletions (7q-) are recurring chromosome abnormalities in leukemic bone marrow cells. In four patients we have previously localized the breakpoints in band 7q22 between the erythropoietin (EPO) and plasminogen activator inhibitor type 1 (PLANH1) genes that map 3 cM apart. The pro alpha 2(I) collagen (COL1A2, in band 7q22) and T cell receptor beta chain genes (TCRB, in band 7q35) have been found undeleted in one patient with an interstitial deletion. Pulsed field gel electrophoresis was used to map the breakpoints more accurately in two patients with a 7q- chromosome. The results suggested that lymphocytes and granulocytes give identical restriction patterns with several enzyme-probe combinations, and that a breakpoint possibly was within 195 kb of EPO in one patient but not in another. The gene order cen-COL1A2-EPO-breakpoint-tel was suggested but physical linkage between COL1A2 and EPO was not found. A new putative TCRB restriction fragment length polymorphism or inherited methylation site was detected.