Runx1 is required for hematopoietic defects and leukemogenesis in Cbfb-MYH11 knock-in mice

RK Hyde, L Zhao, L Alemu, PP Liu - Leukemia, 2015 - nature.com
RK Hyde, L Zhao, L Alemu, PP Liu
Leukemia, 2015nature.com
CBFβ-SMMHC (core-binding factor β-smooth muscle myosin heavy chain), the fusion
protein generated by the chromosome 16 inversion fusion gene, CBFB-MYH11, is known to
initiate leukemogenesis. However, the mechanism through which CBFβ-SMMHC contributes
to leukemia development is not well understood. Previously, it was proposed that CBFβ-
SMMHC acts by dominantly repressing the transcription factor RUNX1 (Runt-related protein
1), but we recently showed that CBFβ-SMMHC has activities that are independent of RUNX1 …
Abstract
CBFβ-SMMHC (core-binding factor β-smooth muscle myosin heavy chain), the fusion protein generated by the chromosome 16 inversion fusion gene, CBFB-MYH11, is known to initiate leukemogenesis. However, the mechanism through which CBFβ-SMMHC contributes to leukemia development is not well understood. Previously, it was proposed that CBFβ-SMMHC acts by dominantly repressing the transcription factor RUNX1 (Runt-related protein 1), but we recently showed that CBFβ-SMMHC has activities that are independent of RUNX1 repression. In addition, we showed that a modified CBFβ-SMMHC with decreased RUNX1-binding activity accelerates leukemogenesis. These results raise questions about the importance of RUNX1 in leukemogenesis by CBFβ-SMMHC. To test this, we generated mice expressing Cbfb-MYH11 in a Runx1-deficient background, resulting from either homozygous Runx1-null alleles (Runx1−/−) or a single dominant-negative Runx1 allele (Runx1+/lz). We found that loss of Runx1 activity rescued the differentiation defects induced by Cbfb-MYH11 during primitive hematopoiesis. During definitive hematopoiesis, RUNX1 loss also significantly reduced the proliferation and differentiation defects induced by Cbfb-MYH11. Importantly, Cbfb-MYH11-induced leukemia had much longer latency in Runx1+/lz mice than in Runx1-sufficient mice. These data indicate that Runx1 activity is critical for Cbfb-MYH11-induced hematopoietic defects and leukemogenesis.
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