Kajigaya, S. . (NIH) McCoy, J. P. (NIH) Tarnowka, M. (NIH) Young, N. S. (NIH) Levin, B. C. Shin, M. G. (BIOTECHNOLOGY DIVISION - 831)
Mitochondrial DNA Sequence Heterogeneity in Circulating Normal Human CD34 Cells and Granulocytes
Blood - June 01, 2004

We have reported marked mitochondrial DNA (mtDNA) sequence heterogeneity among individual CD34 clones from adult bone marrow (BM) and the age-dependent accumulation of mtDNA mutations in this mitotically active tissue (Shin MG et al, Blood 2003; epub). Here we show direct evidence of clonal expansion of cells containing mtDNA mutations and that the mtDNA sequence may be easily determined using peripheral blood (PB) as a CD34 cell source. After single circulating CD34 cells or granulocytes from six individuals were sorted by flow cytometry, approximately 20% of the entire mtDNA genome from several hundred clones or cells was gene amplified and sequenced. Analysis of 594 circulating CD34 clones showed that 150 (25%) had mtDNA sequences different from the same donor’s corresponding aggregate sequence. Examination of single granulocytes indicated that 103 (29%) from the same six individuals showed mtDNA heterogeneity, with sequences distinct from the corresponding aggregate tissue sequence and from the sequences of other single granulocytes. The prevalence of approximately 4% unique nucleotide substitutions in the mtDNA from the BM and PB CD34 cells was found to be similar in the control region and for the cytochrome c oxidase 1 (CO1) and cytochrome B (Cytb) genes. Almost half the mutations in CO1 and Cytb genes resulted in amino acid changes. Circulating and marrow CD34 cells showed virtually identical patterns of mtDNA heterogeneity, and the same changes were seen in progeny granulocytes as in their progenitors, indicating that blood sampling could be utilized in studies to determine whether mtDNA reflects an individual’s cumulative or recent exposure to mutagens; as a marker of individual hematopoietic progenitors, stem cells and their expansion; and for the detection of minimal residual disease in hematologic malignancies of CD34 cell origin.
Keywords: circulating and marrow CD34 , granulocyte , mtDNA mutations , single cell mutations
Total pages: 12. Availability information updated on July 19, 2004.
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