Blood Journal
Leading the way in experimental and clinical research in hematology

An ENU-induced mouse mutant of SHIP1 reveals a critical role of the stem cell isoform for suppression of macrophage activation

  1. Nhu-Y. N. Nguyen1,2,
  2. Mhairi J. Maxwell3,
  3. Lisa M. Ooms4,
  4. Elizabeth M. Davies4,
  5. Adrienne A. Hilton5,
  6. Janelle E. Collinge5,
  7. Douglas J. Hilton5,
  8. Benjamin T. Kile5,
  9. Christina A. Mitchell4,
  10. Margaret L. Hibbs3,
  11. Stephen M. Jane1,2, and
  12. David J. Curtis1,2
  1. 1Rotary Bone Marrow Research Laboratories, Royal Melbourne Hospital, Victoria, Australia;
  2. 2Department of Medicine, University of Melbourne, Victoria, Australia;
  3. 3Department of Immunology, Monash University, Victoria, Australia;
  4. 4Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia; and
  5. 5Molecular Medicine Division, Walter and Eliza Hall Institute of Medical Research, Victoria, Australia

Abstract

In a recessive ENU mutagenesis screen for embryonic lethality, we identified a mouse pedigree with a missense mutation of SHIP1 (SHIP1el20) leading to an amino acid substitution I641T in the inositol-5′-phosphatase domain that represses phosphatidylinositol-3-kinase signaling. Despite detectable expression of functional SHIP1 protein, the phenotype of homozygous SHIP1el20/el20 mice was more severe than gene-targeted SHIP1-null (SHIP1−/−) mice. Compared with age-matched SHIP1−/− mice, 5-week-old SHIP1el20/el20 mice had increased myeloid cells, serum IL-6 levels, marked reductions in lymphoid cells, and died by 7 weeks of age with infiltration of the lungs by activated macrophages. Bone marrow transplantation demonstrated that these defects were hematopoietic-cell-autonomous. We show that the el20 mutation reduces expression in SHIP1el20/el20 macrophages of both SHIP1 and s-SHIP, an isoform of SHIP1 generated by an internal promoter. In contrast, SHIP1−/− macrophages express normal levels of s-SHIP. Compound heterozygous mice (SHIP1−/el20) had the same phenotype as SHIP1−/− mice, thus providing genetic proof that the more severe phenotype of SHIP1el20/el20 mice is probably the result of concomitant loss of SHIP1 and s-SHIP. Our results suggest that s-SHIP synergizes with SHIP1 for suppression of macrophage activation, thus providing the first evidence for a role of s-SHIP in adult hematopoiesis.

  • Submitted January 18, 2011.
  • Accepted February 28, 2011.
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