U2af1 is a haplo-essential gene required for hematopoietic cancer cell survival in mice
Brian A. Wadugu, … , Timothy A. Graubert, Matthew J. Walter
Brian A. Wadugu, … , Timothy A. Graubert, Matthew J. Walter
Published September 21, 2021
Citation Information: J Clin Invest. 2021;131(21):e141401. https://doi.org/10.1172/JCI141401.
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Research Article Hematology Oncology

U2af1 is a haplo-essential gene required for hematopoietic cancer cell survival in mice

Abstract

Somatic mutations in the spliceosome gene U2AF1 are common in patients with myelodysplastic syndromes. U2AF1 mutations that code for the most common amino acid substitutions are always heterozygous, and the retained WT allele is expressed, suggesting that mutant hematopoietic cells may require the residual WT allele to be viable. We show that hematopoiesis and RNA splicing in U2af1 heterozygous knockout mice were similar to those in control mice, but that deletion of the WT allele in U2AF1(S34F) heterozygous mutant–expressing hematopoietic cells (i.e., hemizygous mutant) was lethal. These results confirm that U2AF1 mutant hematopoietic cells are dependent on the expression of WT U2AF1 for survival in vivo and that U2AF1 is a haplo-essential cancer gene. Mutant U2AF1(S34F)-expressing cells were also more sensitive to reduced expression of WT U2AF1 than nonmutant cells. Furthermore, mice transplanted with leukemia cells expressing mutant U2AF1 had significantly reduced tumor burden and improved survival after the WT U2af1 allele was deleted compared with when it was not deleted. These results suggest that selectively targeting the WT U2AF1 allele in heterozygous mutant cells could induce cancer cell death and be a therapeutic strategy for patients harboring U2AF1 mutations.

Authors

Brian A. Wadugu, Sridhar Nonavinkere Srivatsan, Amanda Heard, Michael O. Alberti, Matthew Ndonwi, Jie Liu, Sarah Grieb, Joseph Bradley, Jin Shao, Tanzir Ahmed, Cara L. Shirai, Ajay Khanna, Dennis L. Fei, Christopher A. Miller, Timothy A. Graubert, Matthew J. Walter

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Figure 6

Survival of mutant U2AF1(S34F) hematopoietic cells is dependent on the expression of the residual WT allele and the ratio of U2AF1(WT:S34F) expression.

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Survival of mutant U2AF1(S34F) hematopoietic cells is dependent on the e...
(A) Experimental design of a competitive transplant of whole bone marrow cells from CD45.2 Mx1-Cre, Mx1-Cre U2af1WT/fl, Mx1-Cre U2af1fl/fl, Mx1-Cre U2af1WT/S34F, or Mx1-Cre U2af1fl/S34F mice mixed at a 1:1 ratio with congenic WT CD45.1/45.2 competitor cells followed by transplantation into lethally irradiated congenic WT CD45.1 recipient mice. U2af1 deletion was induced by pIpC, and analysis of the peripheral blood chimerism was performed. (B) Peripheral blood neutrophil chimerism of Mx1-Cre, Mx1-Cre U2af1WT/fl, Mx1-Cre U2af1fl/fl, Mx1-Cre U2af1WT/S34F, and Mx1-Cre U2af1fl/S34F mice (n = 14–16). (C) Experimental design of a competitive transplant of whole bone marrow cells from CD45.2 tgU2AF1(WT)/U2af1WT/WT, tgU2AF1(WT)/U2af1fl/fl, tgU2AF1(S34F)/U2af1WT/WT, or tgU2AF1(S34F)/U2af1fl/fl mice. All the donor test mice have both Mx1-Cre and rtTA. Transgenic U2AF1(WT) and U2AF1(S34F) were induced by 10,000 ppm doxycycline (dox) chow, followed by pIpC-induced U2af1 deletion after 4 weeks, and analysis of the peripheral blood chimerism was performed. (D) Overall peripheral blood and neutrophil chimerism in tgU2AF1(WT)/U2af1WT/WT, tgU2AF1(WT)/U2af1fl/fl, tgU2AF1(S34F)/U2af1WT/WT, and tgU2AF1(S34F)/U2af1fl/fl mice after induction of transgenic U2AF1(WT) or U2AF1(S34F) by 10,000 ppm doxycycline chow and U2af1 deletion induced by pIpC Cre-activation (n = 7–8). (E) Experimental design of a competitive transplant of whole bone marrow cells from CD45.2 Mx1-Cre/rtTA/tgU2AF1(WT)/U2af1WT/S34F (tgU2AF1[WT]/U2af1WT/S34F) mice. Transgenic U2AF1(WT) was induced by 10,000 ppm doxycycline chow starting 2 weeks after transplant, followed by pIpC-induced U2af1 S34F mutant allele activation after 2 weeks of doxycycline chow. Analysis of peripheral blood chimerism was performed. (F) Overall peripheral blood and neutrophil chimerism of tgU2AF1(WT)/U2af1WT/S34F with or without doxycycline chow treatment (n = 9–10). All data are represented as mean ± SD. *P < 0.05; ***P < 0.001, 2-way ANOVA with Šidák’s (B and F) or Tukey’s (D) multiple-comparison test.