Abstract
Functional maintenance of hematopoietic stem cells (HSCs) is constantly challenged by stresses like DNA damage and oxidative stress. Here we show that the Fanconi anemia protein Fancd2 and stress transcriptional factor Foxo3a cooperate to prevent HSC exhaustion in mice. Deletion of both Fancd2 and Foxo3a led to an initial expansion followed by a progressive decline of bone marrow stem and progenitor cells. Limiting dilution transplantation and competitive repopulating experiments demonstrated a dramatic reduction of competitive repopulating units and progressive decline in hematopoietic repopulating ability of double-knockout (dKO) HSCs. Analysis of the transcriptome of dKO HSCs revealed perturbation of multiple pathways implicated in HSC exhaustion. Fancd2 deficiency strongly promoted cytoplasmic localization of Foxo3a in HSCs, and re-expression of Fancd2 completely restored nuclear Foxo3a localization. By co-expressing a constitutively active CA-FOXO3a and WT or a nonubiquitinated Fancd2 in dKO bone marrow stem/progenitor cells, we demonstrated that Fancd2 was required for nuclear retention of CA-FOXO3a and for maintaining hematopoietic repopulation of the HSCs. Collectively, these results implicate a functional interaction between the Fanconi anemia DNA repair and FOXO3a pathways in HSC maintenance.
Highlights
Maintenance of hematopoietic stem cells (HSCs) is challenged by DNA damage and oxidative stress
We demonstrated that deletion of both Fancd2 and Foxo3a in mice induced HSC exhaustion
We provided several pieces of evidence: (i) cell cycle analysis showed a significant decrease in quiescent HSCs in dKO mice compared with WT and Fancd2Ϫ/Ϫ or Foxo3aϪ/Ϫ mice (Fig. 2, C and D); (ii) in vivo BrdU incorporation assay revealed a marked increase in proliferation in dKO CD34ϪLSK cells compared with those from mice with other three genotypes (Fig. 2, E and F); (iii) global gene expression profiling on phenotypic HSC (SLAM) cells exhibited a deregulated cell cycle-associated transcriptional program that was unique to dKO HSCs (Fig. 3, B and C); and (iv) functionally, we demonstrated that a functional Fancd2 was required for nuclear retention of FOXO3a and for HSC maintenance (Figs. 4 and 5)
Summary
Maintenance of HSCs is challenged by DNA damage and oxidative stress. Results: Fancd deficiency promoted cytoplasmic localization of Foxo3a in HSCs. Conclusion: Fancd is required for nuclear retention of Foxo3a and maintaining hematopoietic repopulation of HSCs. Significance: Our results implicate an interaction between FA DNA repair and FOXO3a pathways in HSC maintenance. We show that the Fanconi anemia protein Fancd and stress transcriptional factor Foxo3a cooperate to prevent HSC exhaustion in mice. Deletion of both Fancd and Foxo3a led to an initial expansion followed by a progressive decline of bone marrow stem and progenitor cells. Studies in ATM (ataxia telangiectasia mutated) deficient mice showed progressive BM failure resulting from a defect in HSC function that was associated with elevated reactive oxygen species that induce oxidative stress [7]. We have exploited the genetic relationship between the two proteins by generating Fancd2Ϫ/Ϫ Foxo3aϪ/Ϫ double-knockout (dKO) mice and demonstrating that Fancd cooperates with nuclear Foxo3a to prevent HSC exhaustion
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
