Related Experiment Video
Updated: Aug 9, 2026
A Detailed Protocol for Characterizing the Murine C1498 Cell Line and its Associated Leukemia Mouse Model
Published on: October 14, 2016
A murine Mll-AF4 knock-in model results in lymphoid and myeloid deregulation and hematologic malignancy
Weili Chen1, Quanzhi Li, Wendy A Hudson
1Cancer Center, University of Minnesota, Minneapolis, USA.
Abstract:
The 2 most frequent human MLL hematopoietic malignancies involve either AF4 or AF9 as fusion partners; each has distinct biology but the role of the fusion partner is not clear. We produced Mll-AF4 knock-in (KI) mice by homologous recombination in embryonic stem cells and compared them with Mll-AF9 KI mice. Young Mll-AF4 mice had lymphoid and myeloid deregulation manifest by increased lymphoid and myeloid cells in hematopoietic organs. In vitro, bone marrow cells from young mice formed unique mixed pro-B lymphoid (B220(+)CD19(+)CD43(+)sIgM(-), PAX5(+), TdT(+), IgH rearranged)/myeloid (CD11b/Mac1(+), c-fms(+), lysozyme(+)) colonies when grown in IL-7- and Flt3 ligand-containing media. Mixed lymphoid/myeloid hyperplasia and hematologic malignancies (most frequently B-cell lymphomas) developed in Mll-AF4 mice after prolonged latency; long latency to malignancy indicates that Mll-AF4-induced lymphoid/myeloid deregulation alone is insufficient to produce malignancy. In contrast, young Mll-AF9 mice had predominately myeloid deregulation in vivo and in vitro and developed myeloid malignancies. The early onset of distinct mixed lymphoid/myeloid lineage deregulation in Mll-AF4 mice shows evidence for both "instructive" and "noninstructive" roles for AF4 and AF9 as partners in MLL fusion genes. The molecular basis for "instruction" and secondary cooperating mutations can now be studied in our Mll-AF4 model.
Insights
MLL-AF4 and MLL-AF9 fusion partners in hematopoietic malignancies have distinct roles. MLL-AF4 mice show mixed lymphoid/myeloid deregulation, while MLL-AF9 mice develop myeloid malignancies, revealing instructive roles for these partners.
Area of Science:
- Hematology
- Molecular Biology
- Cancer Research
Background:
- Two frequent human MLL hematopoietic malignancies involve AF4 or AF9 fusion partners.
- The specific role of these fusion partners in disease biology remains unclear.
Purpose of the Study:
- To compare the distinct biological roles of AF4 and AF9 as MLL fusion partners.
- To generate and characterize Mll-AF4 knock-in (KI) mouse models and compare them to Mll-AF9 KI mice.
Main Methods:
- Homologous recombination in embryonic stem cells to produce Mll-AF4 KI mice.
- Comparison of Mll-AF4 KI mice with Mll-AF9 KI mice.
- In vitro analysis of bone marrow cells and in vivo observation of hematopoietic organs and disease development.
Main Results:
- Mll-AF4 mice exhibited early lymphoid and myeloid deregulation with unique mixed pro-B lymphoid/myeloid colonies in vitro.
- Mll-AF4 mice developed mixed lymphoid/myeloid hyperplasia and B-cell lymphomas after a prolonged latency.
- Mll-AF9 mice showed predominantly myeloid deregulation and developed myeloid malignancies.
Conclusions:
- AF4 and AF9 exhibit distinct 'instructive' and 'noninstructive' roles in MLL fusion genes.
- MLL-AF4-induced deregulation alone is insufficient for malignancy, suggesting secondary cooperating mutations are necessary.
- The Mll-AF4 model provides a platform for studying the molecular basis of instruction and cooperating mutations in MLL fusion-driven leukemogenesis.
