title: An ENU-induced mouse mutant of SHIP1 reveals a critical role of the stem cell isoform for suppression of macrophage activation.
abstract: In a recessive ENU mutagenesis screen for embryonic lethality, we identified a mouse pedigree with a missense mutation of SHIP1 (SHIP1(el20)) 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 SHIP1(el20/el20) mice was more severe than gene-targeted SHIP1-null (SHIP1(-/-)) mice. Compared with age-matched SHIP1(-/-) mice, 5-week-old SHIP1(el20/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 SHIP1(el20/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 SHIP1(el20/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.
authors.affiliation: Rotary Bone Marrow Research Laboratories, Royal Melbourne Hospital, Victoria 3050, Australia.
authors.forename: Nhu-Y N
authors.initials: NY
authors.lastname: Nguyen
authors.forename: Mhairi J
authors.initials: MJ
authors.lastname: Maxwell
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Ooms
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Davies
authors.forename: Adrienne A
authors.initials: AA
authors.lastname: Hilton
authors.forename: Janelle E
authors.initials: JE
authors.lastname: Collinge
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Hilton
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Kile
authors.forename: Christina A
authors.initials: CA
authors.lastname: Mitchell
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Hibbs
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Jane
authors.forename: David J
authors.initials: DJ
authors.lastname: Curtis
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D016026:Bone Marrow Transplantation; D017931:DNA Primers / Q000235:genetics; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D005038:Ethylnitrosourea; D005260:Female; D005808:Genes, Recessive; D006410:Hematopoiesis / Q000235:genetics / Q000502:physiology; D006720:Homozygote; D000072181:Inositol Polyphosphate 5-Phosphatases; D015850:Interleukin-6 / Q000096:biosynthesis; D008262:Macrophage Activation / Q000235:genetics* / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D016296:Mutagenesis; D020125:Mutation, Missense; D010641:Phenotype; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D020033:Protein Isoforms / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction
chemical_list: D017931:DNA Primers; D015850:Interleukin-6; D020033:Protein Isoforms; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606433:Inpp5d protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D005038:Ethylnitrosourea