Hematopoietic compartment of Fanconi anemia group C null mice contains fewer lineage-negative CD34+ primitive hematopoietic cells and shows reduced reconstruction ability.

Fanconi anemia (FA) is a complex recessive genetic disease that causes bone marrow failure in children. The mechanism by which the gene for FA group C (Fancc) impinges on the normal hematopoietic program is unknown. Here we demonstrate that the bone marrow from Fancc-/- mice have reduced ability for primary and secondary long-term reconstitution of myeloablated recipients compared to wild-type or heterozygous mice, indicating that the Fancc gene product is required for the maintenance of normal numbers of hematopoietic stem cells. Long-term and secondary transplant studies suggested that there also were qualitative changes in their developmental potential. Consistent with the reduction in reconstitution, flow cytometric analysis of the primitive subfractions of hematopoietic cells obtained from the bone marrow of Fancc -/- mice demonstrated that they contained 40 to 70% fewer lineage-negative (Lin-)Thy1.2-/lowScal(+) c-Kit(+)CD34+ cells compared to controls. In contrast, the number of Lin Thy1.2-/ lowScal(+)c-Kit CD34(-)cells was comparable to that of wild-type mice. The differential behavior of Lin(-)Thy1.2-/lowScal+c-Kit+CD34+ and Lin(-)Thy1.2-/lowScal(+)c-Kit CD34 subfractions also was observed in mice treated with the DNA cross-linking agent mitomycin C(MMC). Fancc-/- mice treated with MMC had an 92% reduction of CD34 cells as compared to Fancc+/+ mice. The number of CD34 cells only was reduced about 20%. These results suggest that the Fancc gene may act at a stage of primitive hematopoietic cell development identified by CD34 expression.