DNA degradation during maturation of erythrocytes – molecular cytogenetic characterization of Howell-Jolly bodies

Abstract

Howell-Jolly bodies (HJBs) are small DNA-containing inclusions of erythrocytes and are often present after splenectomy. The genetic composition of HJBs is unknown at present. We isolated individual erythrocytes that had inclusion bodies from five splenectomized patients and performed DNA amplification using degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) with subsequent reverse painting on normal male metaphase spreads. We also measured the sizes of HJBs in erythrocytes from a splenectomized patient using an inverted microscope. Two-dimensional positions of HJBs were projected onto a virtual erythrocyte. The average size of HJBs was 0.73 ± 0.17 µm (range 0.4–1.1 µm). Inside the erythrocyte the HJBs were found to be equally distributed. Small HJBs contained DNA from one or two centromeres and larger HJBs contained DNA from up to eight different centromeres. Centromeric DNA from chromosomes 1/5, 7, 8, and 18 was most frequently observed. Signals from the centromeric regions of chromosomes 3, 4, 9, and 10 were not observed. Signals from euchromatic regions were detected in a few cases. We hypothesize that in addition to enucleation and nucleus fragmentation DNA degradation during maturation of erythrocytes preferentially eliminates euchromatic DNA. Similarities between these processes and those described for embryonic stem cells suggest that most stem cells are able to degrade DNA in a genetically controlled manner.