Microphthalmia transcription factor expression contributes to bone marrow failure in Fanconi anemia
Alessia Oppezzo, … , Patrycja Pawlikowska, Filippo Rosselli
Alessia Oppezzo, … , Patrycja Pawlikowska, Filippo Rosselli
Published December 26, 2019
Citation Information: J Clin Invest. 2020;130(3):1377-1391. https://doi.org/10.1172/JCI131540.
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Research Article Cell biology Hematology

Microphthalmia transcription factor expression contributes to bone marrow failure in Fanconi anemia

Abstract

Hematopoietic stem cell (HSC) attrition is considered the key event underlying progressive BM failure (BMF) in Fanconi anemia (FA), the most frequent inherited BMF disorder in humans. However, despite major advances, how the cellular, biochemical, and molecular alterations reported in FA lead to HSC exhaustion remains poorly understood. Here, we demonstrated in human and mouse cells that loss-of-function of FANCA or FANCC, products of 2 genes affecting more than 80% of FA patients worldwide, is associated with constitutive expression of the transcription factor microphthalmia (MiTF) through the cooperative, unscheduled activation of several stress-signaling pathways, including the SMAD2/3, p38 MAPK, NF-κB, and AKT cascades. We validated the unrestrained Mitf expression downstream of p38 in Fanca–/– mice, which display hallmarks of hematopoietic stress, including loss of HSC quiescence, DNA damage accumulation in HSCs, and reduced HSC repopulation capacity. Importantly, we demonstrated that shRNA-mediated downregulation of Mitf expression or inhibition of p38 signaling rescued HSC quiescence and prevented DNA damage accumulation. Our data support the hypothesis that HSC attrition in FA is the consequence of defects in the DNA-damage response combined with chronic activation of otherwise transiently activated signaling pathways, which jointly prevent the recovery of HSC quiescence.

Authors

Alessia Oppezzo, Julie Bourseguin, Emilie Renaud, Patrycja Pawlikowska, Filippo Rosselli

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Figure 4

Fanca–/– mice display altered BM homeostasis.

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Fanca–/– mice display altered BM homeostasis. (A) Schematic representat...
(A) Schematic representation of the HSC hierarchy and colony stages. (B) Gating strategy for the analysis of the LSK fraction and its 3 subpopulations, long-term HSCs (LT-HSCs, Flt3–CD34–), short-term HSCs (ST-HSCs, Flt3–CD34+), and multipotent progenitors (MPPs, Flt3+CD34+). (C) Percentages of LSK cells, LT-HSCs, ST-HSCs, and MPPs calculated among the total numbers of Lin– cells in young (3 to 6 months old) and old (more than 1 year old) WT and Fanca–/– mice. Each point represents a single mouse. (D) WT and Fanca–/– CFUs of different colony types after LSK plating and 7 days of culture (n = 3). (E) Bottom left: representative images after immunohistochemical staining of GFP-positive cells in the BM sections of recipients. Bottom right: graph of donor chimerism in the circulating blood 4 weeks after LSK+ competitor transplants (n = 3). Scale bars: 50 μm. Statistical significance was assessed using an unpaired 2-tailed t test with Welch’s correction (C, D, and E). *P < 0.05; **P < 0.01.