Endogenous DNA Damage Leads to p53-Independent Deficits in Replicative Fitness in Fetal Murine Fancd2 −/− Hematopoietic Stem and Progenitor Cells

Abstract

SummaryOur mechanistic understanding of Fanconi anemia (FA) pathway function in hematopoietic stem and progenitor cells (HSPCs) owes much to their role in experimentally induced DNA crosslink lesion repair. In bone marrow HSPCs, unresolved stress confers p53-dependent apoptosis and progressive cell attrition. The role of FA proteins during hematopoietic development, in the face of physiological replicative demand, remains elusive. Here, we reveal a fetal HSPC pool in Fancd2−/− mice with compromised clonogenicity and repopulation. Without experimental manipulation, fetal Fancd2−/− HSPCs spontaneously accumulate DNA strand breaks and RAD51 foci, associated with a broad transcriptional DNA-damage response, and constitutive activation of ATM as well as p38 stress kinase. Remarkably, the unresolved stress during rapid HSPC pool expansion does not trigger p53 activation and apoptosis; rather, it constrains proliferation. Collectively our studies point to a role for the FA pathway during hematopoietic development and provide a new model for studying the physiological function of FA proteins.

Studies in an Early Development Window Unveils a Severe HSC Defect in both Murine and Human Fanconi Anemia

“…This dysregulation is also observed in human FA FL HSCs ( Table S2 ). In line with the results described for Fancd2 −/− E14.5 FL HSCs ( Suzuki et al., 2017 , Yoon et al., 2016 ), p53 gene is significantly downregulated both in Fancg −/− and FA fetal HSCs. In a genotoxic stress model, Milyavsky et al.…”

“…This HSC qualitative defect persists in Fancg −/− FL at E14.5, as described by others for Fancc −/− and Fancd2 −/− ( Kamimae-Lanning et al., 2013 , Suzuki et al., 2017 , Yoon et al., 2016 ). An HSC-enriched LSA population sorted from Fancg −/− and WT E14.5 FL was injected into lethally irradiated primary CD45.1 mice.…”

“…The hypothesis that FA BMF could take its origin in utero was suggested by the study of Ceccaldi et al. (2012) and was corroborated by studies of fetal hematopoiesis in E14.5 Fancc −/− and Fancd2 −/− FL ( Kamimae-Lanning et al., 2013 , Suzuki et al., 2017 , Yoon et al., 2016 ). In the present work, we followed hematopoiesis in Fancg −/− mice using state-of-the-art experimental hematopoiesis assays including long-term engraftment experiments on highly purified mouse and human cells.…”

“…However, a deficit in the CD34 + cell numbers in FA subjects is observed very early during childhood, even before the onset of the BMF clinical symptoms ( Ceccaldi et al., 2012 , Kelly et al., 2007 ). This, added to the early developmental defects of the hematopoietic commitment described for human embryonic stem cells after knockdown of FANCA and FANCD2 genes, led us and others to hypothesize that the FA hematopoietic defect could already begin in utero ( Ceccaldi et al., 2012 , Kamimae-Lanning et al., 2013 , Suzuki et al., 2017 , Tulpule et al., 2010 , Yoon et al., 2016 ).…”

Abnormal migration behavior linked to Rac1 signaling contributes to primordial germ cell exhaustion in Fanconi anemia pathway-deficient Fancg−/− embryos

“…The genomic integrity of stem cells is fundamental for the establishment of the stem cell pool, and some DNA repair abnormalities are linked to stem cell dysfunction (4). As FA is a DNA repair syndrome, the FA pathway is involved in neural and hematopoietic progenitor/stem cell failure during fetal and adult life (5)(6)(7)(8)(9)(10). However, increased production of reactive oxygen species, abnormal activation of stress-activated protein kinase or TGFβ and enhanced sensitivity to endogenous aldehyde or cytokines such as tumor necrosis factor-alpha and interferongamma have also been reported to play a role in FA pathology (11)(12)(13)(14)(15)(16)(17).…”