Total Fancd2 subscriber percentage in peripheral blood was observed to be higher than in the granulocyte population. liver cells display similar functional defects toFancd2adult bone marrow cells including reduced colony forming units, increased mitomycin C sensitivity, increased LT-HSC apoptosis and heavily impaired competitive repopulation, implying these defects are intrinsic to the fetal liver and not dependent on the accumulation of DNA damage during aging. Telomere shortening, an aging-related mechanism proposed to contribute to HSC apoptosis and bone marrow failure in FA, was not observed inFancd2KO fetal livers. In summary, loss ofFancd2yields significant defects to fetal liver hematopoiesis, particularly the HSC population, which mimic key phenotypes from adultFancd2KO bone marrow independent of aging-accrued DNA damage. Keywords: Fanconi Anemia, bone marrow failure, hematopoietic stem cell, telomere dysfunction, DNA repair, fetal hematopoiesis == Graphical abstract == == Introduction == Hematopoietic manifestations from Fanconi Anemia (FA) can begin in early childhood, but often increase in prevalence and severity with age(13). The progression of disease is thought to reflect underlying defects in DNA repair. The molecular defects in FA patients have been identified at least 20 individual genes all with hypersensitivity Rabbit Polyclonal to FPRL2 to DNA interstrand crosslinking (ISL) agents (2, 4, 5). Supporting that FA genes function in a common pathway, mutations occurring in members of the FA core complex, such asFancc, interfere AB05831 with monoubiquitylation of Fancd2 in response to DNA damage, leading to unrepaired DNA damage and genomic instability. As patients age, progressive bone marrow failure occurs in 90% by age 40 (2). Although anemia appears at a median of 7 years of age, evidence has been accumulating that defects in hematopoiesis occur earlier in development. It has been hypothesized insufficient seeding of the bone marrow from FA fetal liver hematopoietic stem cells (HSCs) leads to bone marrow failure later in life. This implies that the buildup of DNA damage over time is not solely responsible for hematopoietic dysfunction and that FA cells possess additional intrinsic pathophysiologic properties (3, 5). From very early childhood, prior to declines in peripheral blood counts, FA patients have low CD34+bone marrow populations suggesting loss AB05831 of bone marrow function has been occurring from the fetal period (3, 6). Fetal defects have been found to be exacerbated by endogenous aldehydes andAldh2deletion within murineFancaorFancd2knockout (KO) embryos was shown to cause a reduction in hematopoiesis that extended into adulthood (7, 8). Examination of a mouseFanccKO model demonstrated defects in fetal liver AB05831 hematopoiesis including low total cellularity and poor transplantability (9). Total HSC numbers in theFanccKO fetal liver, however , were found to be preserved, similar to findings in young adultFanccKO bone marrow (10, 11) In contrast, adultFancd2KO murine bone marrow has a more severe phenotype, demonstrating earlier HSC loss and reduced competitive repopulation ability in comparison to adultFanccKO bone marrow (1013). The more severeFancd2KO phenotype may result from the central coordinating function of Fancd2 in FA pathways for which upstream FA proteins, such as Fancc serve to regulate (5, 14). This raises the possibility that there might be distinct differences withinFancd2KO fetal hematopoiesis contributing to AB05831 defects withinFancd2KO adult bone marrow. We therefore investigated the immunophenotypic and functional effects ofFancd2deletion on the fetal liver and the HSC compartment in order to define the early consequences ofFancd2loss on embryonic hematopoiesis. == Materials and Methods == == Animals == Fancd2KO mice were obtained and PCR genotyped as previously described (15). Mice were maintained as heterozygotes in a pure C57BL/6 background. Wild-type C57BL/6 CD45. 2 mice were bred with B6. SJL CD45. 1 mice to generate CD45. 1/CD45. 2 heterozygote mice used as competitors in transplantation studies. CD45. 2 C57BL/6 mice and CD45. 1 B6. SJL recipient mice were obtained from The Jackson Laboratory. All animal studies were carried out in accordance with and with approval from the University of Massachusetts Medical School Institutional Animal Care AB05831 and Use Committee. == Flow Cytometry == Lineage, c-Kit, Sca-1 and CD34 staining was performed as previously described and run on a BD Biosciences LSR II flow cytometer (16). Analysis was performed using FlowJo software (Treestar). For H2AX analysis, cells were surface-stained and then fixed and stained using Cytofix/Cytoperm and Perm Plus buffer (BD Biosciences) according to the manufacturers protocol with anti-H2AX pS139-PE or control antibody (BD Biosciences). For apoptosis analysis, cells were surface-stained and then stained according to the manufacturers protocol using the PE Annexin V Apoptosis Detection Kit I (BD Biosciences). Peripheral blood flow cytometry was performed as previously described using anti-CD45. 1-PE, anti-CD45. 2-FITC or anti-CD45. 2 APC, anti-Gr1-APC-Cy7, and anti-Mac-1-PE-Cy7 (BD Biosciences) (16). 7-AAD was used to differentiate between live and dead cells in all experiments (BD Biosciences). == Bone marrow/fetal liver transplantation == Competitive repopulation.
