UBTF串联重复对造血和白血病发生的体内影响

This study aims to investigate hematopoietic and leukemic development in a physiological UBTF-tandem duplication (TD) model to better understand the biology underlying this subtype-defining alteration of acute myeloid leukemia (AML). UBTF-TDs are characterized as somatic, heterozygous, in-frame tandem duplications (TDs) within exon 13 of UBTF (upstream binding transcription factor). These alterations are associated with an overall inferior outcome. We developed a conditional knock-in mouse in which Ubtf-TD is expressed from the endogenous Ubtf locus after recombination by Cre recombinase driven by the hematopoietic Vav promoter, recapitulating the somatic mutation observed in patients. We first assessed the self-renewal potential of hematopoietic stem progenitor cells (HSPCs) from 8-10-week mice using colony-forming unit (CFU) assays. To assess leukemic burden, we monitored peripheral blood using flow cytometry and complete blood cell count. The hematopoietic compartments (bone marrow and spleen) from mice that progressed to terminal disease were examined by RNA sequencing (RNA-Seq) to characterize the expression profiles. Tumors that developed were transplanted into sub-lethally irradiated recipient mice to assess their engraftment potential. To investigate hematopoietic development in Ubtf-TD mice, we performed a comprehensive cellular and molecular characterization using multiparameter flow cytometry. We then performed single-cell RNA-seq to examine pre-leukemic progression. Finally, to explore functional dependencies of murine Ubtf-TD tumor cells, we conducted in vitro CRISPR knockout (KO) screens of 210 genes prioritized from RNA-seq data, UBTF-TD cord-blood CD34 (cbCD34) functional studies, and key UBTF-TD AML genes. Murine HSPCs expressing Ubtf-TD exhibit increased self-renewal capacity both in vitro and in vivo . Ubtf-TD expression induces a myeloid leukemia by 45 weeks of age. Clinical features include elevated white blood cell counts, anemia, and splenomegaly. Phenotypically, these leukemias exhibit high levels of CD11b and Gr-1 expression, are serially transplantable, and have dysregulated Hoxa/Hoxb gene expression. Flow cytometry further reveals increases in the granulocyte-monocyte progenitor (GMP) and multipotent progenitor (MPP3) populations in Ubtf-TD mice. Dependency screens revealed that Ubtf-TD cells rely on Xpo1 , Men1, Kmt2a, and Meis1 . Collectively, our work demonstrates that UBTF-TD is sufficient to drive leukemia development in vivo and that this model recapitulates key phenotypes observed in UBTF-TD AMLs. This mouse model provides a platform for evaluating leukemia initiation, progression, and therapeutic vulnerabilities, including XPO1 inhibition (eltanexor) and Menin inhibition (revumenib), both of which have demonstrated efficacy in cbCD34 and patient-derived xenograft (PDX) UBTF-TD models.