FAC IN STEM CELL FUNCTION AND OXYGEN SENSITIVITY

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Fanconi anemia (FA) is a complex, autosomal recessive disorder characterized by bone marrow (BM) failure, increased incidence of malignancies, and hypersensitivity to bifunctional alkylating agents such as mitomycin C (MMC). There are eight complementation types of FA that have overlapping phenotypes inferring the existence of eight genes in a common biochemical pathway. It is clear that the hematopoietic progenitor compartment is affected by loss of Fanconi anemia complementation type C protein (FAC). However, no direct studies have been conducted evaluate whether the hematopoietic stem cell (HSC) compartment is similarly affected due to difficulties in assessing HSC function in the human system. The development of a murine model containing a homozygous disruption in the murine homologue (Fac) of FAC allows comprehensive evaluation of this question. Using this murine model, we showed that Fac -/- hematopoietic progenitors were hypersensitive to MMC, similar to FA patients. These data suggest that Fac -/- mice will be a good model system to study FA. Several lines of evidence suggest that FA proteins may have a role in maintaining normal oxidative metabolism. In addition, the recent observation in COS cells that FAC modulates NADPH:cytochrome p450 reductase (RED) activity, an important enzyme that generates oxygen radicals and activates several drugs such as MMC supports this hypothesis. The goals of this application are: 1) to determine whether loss of Fac affects HSC function, 2) to determine if Fac -/- hematopoietic cells have an increased sensitivity to oxidative stress, and 3) to evaluate whether overexpression of RED induces a hypersensitivity to oxidative stresss in Fac +/+ cells. These data will provide important information in elucidating the pathogenesis of BM failure and carcinogenesis in FA as well as investigate a distinct function of Fac in normal oxidative metabolism that could provide potential implications for modifying current treatment protocols for FA patients.