Mll partial tandem duplication induces aberrant Hox expression in vivo via specific epigenetic alterations

J Clin Invest. 2006 Oct;116(10):2707-16. doi: 10.1172/JCI25546. Epub 2006 Sep 14.


We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll(PTD/WT) mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll(PTD/WT) mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / genetics
  • Cell Proliferation
  • Cell Transformation, Neoplastic / genetics
  • Epigenesis, Genetic / genetics*
  • Gene Duplication*
  • Gene Expression / genetics*
  • Gene Rearrangement / genetics
  • Genotype
  • Hematopoiesis / genetics
  • Hematopoietic Stem Cells / metabolism
  • Hematopoietic Stem Cells / pathology
  • Histone-Lysine N-Methyltransferase
  • Histones / metabolism
  • Homeobox A10 Proteins
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Myeloid-Lymphoid Leukemia Protein / genetics*
  • Neoplasm Proteins / genetics
  • Phenotype
  • Promoter Regions, Genetic / genetics
  • Ribs / abnormalities
  • Ribs / metabolism
  • Tandem Repeat Sequences / genetics*


  • Histones
  • Homeobox A10 Proteins
  • Homeodomain Proteins
  • Hoxa7 protein, mouse
  • Neoplasm Proteins
  • Myeloid-Lymphoid Leukemia Protein
  • HoxA protein
  • Hoxa10 protein, mouse
  • Histone-Lysine N-Methyltransferase
  • Kmt2a protein, mouse