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 Article has an altmetric score of 1

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 7

Mitf downregulation or p38 inhibition normalizes gene expression in Fanca–/– or Fancc–/– cells.

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Mitf downregulation or p38 inhibition normalizes gene expression in Fanc...
(A) qRT-PCR analysis of Mitf, Puma, Noxa, and Impdh2 expression in WT, Fanca–/–, or Fancc–/– MEFs under basal conditions after siRNA-mediated MiTF downregulation or a 2-hour treatment with the p38 inhibitor SB203580. In each individual experiment, Mitf, Puma, Noxa, and Impdh2 expression were first normalized to that of Oaz1 (internal control) and then normalized to the Mitf, Puma, Noxa, or Impdh2/Oaz1 ratio of the WT MEFs, which was set as 1 in each experiment. Data are shown as mean ± SEM of n = 5 experiments. (B) qRT-PCR analysis of Fancc expression in WT or in Fanca–/– MEFs under basal conditions after siRNA-mediated Mitf downregulation or a 2-hour treatment with the p38 inhibitor SB203580. (C) Schematic model combining our observations with state-of-the-art knowledge concerning the effects of FANC pathway inactivation on BM homeostasis. Statistical significance was assessed using 1-way ANOVA with Dunnett’s (A) or Bonferroni’s (B) correction. *P < 0.05; **P < 0.01; ***P < 0.001.