Identification of a subclass of double minute chromosomes containing centromere-associated DNA

In a study of abnormal chromosomes in non-Hodgkin's lymphoma (NHL) cells we have identified one case which contained extrachromosomal chromatin bodies that, on the basis of their morphology and negative C-banding, appeared to be double minute chromosomes (dmin). However, fluorescence in-situ hybridization (FISH) analysis using an X-specific centromeric alphoid repeat probe and a pan-centromere probe, clearly demonstrated the presence of centromere-associated DNA in these dmin. FISH analysis with the pan-centromere probe of the dmin in neuroblastoma and sarcoma cells failed to reveal the presence of centromere-associated DNA, but analysis of two cases of acute myeloid leukemia cells revealed centromere-associated DNA in 25% of their dmin. These data indicate the existence of dmin that contain centromere-associated DNA and suggest that such dmin might represent a new class of extrachromosomal chromatin bodies.