Generation And Characterization Of Mouse Models Of Leukemia-related Genetic Abnormalities And Study Of Underlying Mechanisms

Acute myeloid leukemia(AML) is a group of hematological malignancies with high heterogeneity.Gene mutations and chromosomal translocations induced fusion genes are crucial in the evaluation of AML patients and in guiding rational management.Chronic myeloid leukemia(CML) evolves from a chronic phase characterized by the Philadelphia chromosome as the sole genetic abnormality into blast crisis,which is often associated with additional chromosomal and/or molecular secondary changes.In this study,we mainly focus on the effect of two genetic abnormalities on hemopoietic system by mouse models.NUP98-IQCG fusion gene was first cloned in a t(3;11) patient with acute myeloid/T lymphoid bi-phenoleukemia,another GATA2 L359V mutation was identified in CML patients with blast transformation.The NUP98 gene located at chromosome 11p15 has been reported to fuse with about34 different partner genes by translocations in hematological malignancies.Transgenic or retrovirus-mediated bone marrow transplantation mouse models reveal the leukemogenesis of some NUP98-related fusion genes,while the leukemogenic ability of NUP98-IQCG has not yet been confirmed.Herein,we demonstrate that transplantation of bone marrow cells expressing NUP98-IQCG induces a penetrable acute myelomonocytic leukemia in recipient mice;this leukemia has a phenotype similar to that of the t(3;11) patient,thus suggesting that NUP98-IQCG could act as a disease driver.RNA-Seq analysis reveals strong upregulation of the Hoxa and Hoxb cluster genes and four opposite-strand RNAs(OS-RNAs) in the vicinity of these clusters,accompanied by the high expression of the Hox cofactor Pbx3 in the leukemic mice.We infer that the Hox/Pbx3 pathway may be the dominant mechanism underlying the leukemogenesis of NUP98-IQCG.Results also reveal that NUP98-IQCG can inhibit the CRM1-mediated nuclear export,and might result in p65 and IQCG nuclear accumulations,as well as the dysregulation of NF-κB and calcium signaling pathways,thereby contributing to leukemogenesis.In the second part,we established a Gata2 L359V knock-in mouse model to investigate the function of Gata2 L359V in vivo.The embryos with a homozygous Gata2 L359V mutant exhibit developmental retardation and severe anemia and die at embryonic day 11-11.5(E11-11.5) .Gata2 L359V heterozygous mice grow and reproduce normally and have no obvious abnormal phenotype under steady-state conditions.However,the heterozygous mice exhibit a delay in regeneration of the hematopoietic system after cytotoxic drug challenge.Moreover,competitive bone marrow transplantation further confirmed the compromised self-renewal ability of Gata2 L359V heterozygous HSCs.RNA-Seq analyses of the yolk sacs at E9.5 and the LSK(Lin~-Sca1~+c-kit~+) cells in adult bone marrow were performed to clarify the underlying mechanisms.And we speculate that dysregulated Notch and Wnt pathways may influence the emergence of HSCs in AGM of homozygous mutant embryos at midgestation and the maintenance of the HSCs of heterozygous mutant adult mice.