Progressive bone marrow failure is a major cause of morbidity and mortality in human Fanconi Anemia patients. In an effort to develop a Fanconi Anemia murine model to study bone marrow failure, we found that Fancd2 ؊/؊ mice have readily measurable hematopoietic defects. Fancd2 deficiency was associated with a significant decline in the size of the c-Kit ؉ Sca-1 ؉ Lineage ؊ (KSL) pool and reduced stem cell repopulation and spleen colony-forming capacity. Fancd2 ؊/؊ KSL cells showed an abnormal cell cycle status and loss of quiescence. In addition, the supportive function of the marrow microenvironment was compromised in Fancd2 ؊/؊ mice. Treatment with Sirt1-mimetic and the antioxidant drug, resveratrol, maintained Fancd2 ؊/؊ KSL cells in quiescence, improved the marrow microenvironment, partially corrected the abnormal cell cycle status, and significantly improved the spleen colony-forming capacity of Fancd2 ؊/؊ bone marrow cells. We conclude that Fancd2 ؊/؊ mice have readily quantifiable hematopoietic defects, and that this model is well suited for pharmacologic screening studies.
IntroductionFanconi anemia (FA) is a rare, autosomal, recessive genetic disorder associated with severe birth defects, cancer predisposition, and bone marrow failure. Thirteen causative genes (FANCA, FANCB, FANCC, FANCD1/BRCA2, FANCD2, FANCE, FANCF, FANCG/XRCC9, FANCI, FANCL/PHF9/Pog, FANCJ/BRIP1/BACH1, FANCM/Hef, and FANCN/ PALB2) have been identified and cloned to date, and the encoded proteins are believed to work together in a common DNA damageresponse pathway to maintain genomic integrity and protect the genome from DNA damage induced by cross-linking agents. 1,2 Although deficiency in DNA cross-link repair renders all FA cells susceptible to cross-linking agents, bone marrow is the most affected organ system. Mutations in any of the different FA genes almost universally lead to bone marrow failure, which is the primary cause of mortality in FA. 3 The pathogenesis of bone marrow failure in FA remains elusive. Mutations in several genes involved in DNA damage repair, including Atr, XPD, and Ercc1, caused either hematopoietic stem cell (HSC) loss or impaired HSC function under conditions of stress. [4][5][6] These studies suggest that the maintenance of genome integrity is critical for HSC survival and function. However, the extent to which genotoxicity, resulting from impaired DNA damage repair, contributes to bone marrow failure in FA is unclear. 7 Other pathways associated with hematopoietic failure, such as altered cytokine signaling, may also contribute to FA pathogenesis. 8,9 For example, levels of proapoptotic cytokines tumor necrosis factor-␣ (TNF-␣) and interferon-␥ (IFN-␥) are elevated in FA lymphocytes, bone marrow cells, and FA patient serum samples. 10-12 FA bone marrow cells (at least of the C complementation group) are also hypersensitive to these cytokines and undergo apoptosis when exposed to even low levels of them. [13][14][15] To better understand FA, multiple murine knockout models, includingand Fancl Ϫ/Ϫ m...