Fanconi Anemia (FA) is an autosomal recessive disease characterized by congenital defects, crosslinker hypersensitivity, progressive bone marrow failure, and a defect in hematopoietic stem cell (HSC) function. There are thirteen known Fanconi Anemia genes (A, B, C, D1, D2, E, F, G, I, J, L, M, N) and disruption of these genes appears to account for a variable degree of HSC dysfunction. Another gene (Usp1), encoding a deubiquitinating enzyme which is not a FA gene per se, is a critical regulator of the FA pathway. Understanding the mechanism of action of the FA proteins may allow better diagnosis and treatment for Fanconi Anemia and other aplastic anemia patients. Here, we have characterized mouse models for FA, including Fancd2−/− and Usp1 −/− mice. Similar to a previously reported Fancd2 mouse model (

Houghtaling S et al,
Genes & Development
,
17
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2021
–2035,
2003
), the Fancd2−/− mice developed in our laboratory displayed FA phenotypes including cellular hypersensitivity to mitomycin C (MMC), hypogonadism and reduced fertility. Interestingly, Usp1−/− mice developed for the first time in our laboratory exhibited severe FA phenotypes, with increased cellular hypersensitivity to MMC, 80% perinatal lethality, testicular atrophy, and depletion of germ cells. Quantitative assessment of the Fancd2 protein expression in the bone marrow using the AQUA imaging system demonstrated low levels of Fancd2 staining in the Lin+ cells compared to the Lin− cells in wild-type (WT) mice, with an absence of Fancd2 expression in the Fancd2 −/− mice. Analysis of hematopoietic parameters in both the Fancd2 and Usp1 mouse models showed normal white blood cell counts and normal hemoglobin levels in the peripheral blood. However, bone marrow from Fancd2−/− mice as well as Usp1−/− mice exhibited phenotypic and functional differences compared to the bone marrow from WT mice. Multiparameter flow cytometric analysis of bone marrow revealed increased frequencies of MEPs (megakaryocyte-erythroid progenitors) in Usp1−/− mice and decreased frequencies of LSK (Lin-Sca-1+Kit+) population in Fancd2−/− mice in comparison to WT controls. In addition, bone marrow from both Fancd2−/− mice and Usp1−/− mice contained significantly reduced frequencies of late-developing day 28 CAFCs (cobblestone area-forming cells) compared to the bone marrow from WT mice. Furthermore, lethally irradiated recipients transplanted with bone marrow from Fancd2−/− or Usp1−/− mice showed reduced donor-type blood cell chimerism at 16 weeks post-transplant, compared to the recipients transplanted with WT bone marrow. Collectively, our data indicate that mice deficient in Fancd2 or Usp1 have hematopoietic stem cell defects and that these mouse models can be useful for development of therapeutics for FA.

Topics:
fanconi anemia, hematopoietic stem cells, mice, hypersensitivity, aplastic anemia, congenital abnormality, deubiquitinating enzymes, diagnostic imaging, hemoglobin measurement, hypogonadism

Disclosures: No relevant conflicts of interest to declare.

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2008, The American Society of Hematology
2008
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