Mitochondrial DNA Sequence Heterogeneity of Single CD34⁺ Cells after Nonmyeloablative Allogeneic Stem Cell Transplantation

¹ Hematology Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892
² Flow Cytometry Core Facility, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892

^* To whom correspondence should be addressed. E-mail: yaoy3{at}nhlbi.nih.gov.

	Abstract

We applied a single-cell method to detect mtDNA mutations in order to evaluate the reconstitution of hematopoietic stem cells (HSC) and committed progenitor cells after nonmyeloablative allogeneic stem cell transplantation in humans. In a total of 1958 single CD34⁺ cells from six HLA-matched sibling donor and recipient pairs, individual CD34⁺ clones were recognized based on the observed donor- or recipient-specific mtDNA sequence somatic alteration. There was no overall reduction of mtDNA heterogeneity among CD34⁺ cells from the recipient after transplantation. Samples collected from two donors over time showed the persistence of certain CD34⁺ clones marked by specific mutations. Our results demonstrate the feasibility of distinguishing donor and recipient individual CD34⁺ clones based on mtDNA mutations during engraftment. HSCs were not limited in number, and similar mtDNA heterogeneity levels suggested representation of the total stem cell compartment during rapid hematopoietic reconstitution in the recipient.