title: Genetic reduction of class IA PI-3 kinase activity alters fetal hematopoiesis and competitive repopulating ability of hematopoietic stem cells in vivo.
abstract: Class I(A) phosphatidylinositol-3 kinase (PI-3K) is a lipid kinase, which is activated in blood cells by hematopoietic growth factors. In vitro experiments using chemical inhibitors of PI-3K suggest that this kinase is potentially important for hematopoietic stem and progenitor cell (HSC/P) function, and recent studies identify PI-3K as a therapeutic target in treating different leukemias and lymphomas. However, the role of PI-3K in regulating fetal liver or adult hematopoiesis in vivo is unknown. Therefore, we examined PI-3K-deficient embryos generated by a targeted deletion of the p85alpha and p85beta regulatory subunits of PI-3K (p85alpha-/-p85beta+/-). The absolute frequency and number of hematopoietic progenitor cells were reduced in p85alpha-/- p85beta+/- fetal livers compared with wild-type (WT) controls. Further, p85alpha-/-p85beta+/- fetal liver hematopoietic stem cells (HSCs) had decreased multilineage repopulating ability in vivo compared with WT controls in competitive repopulation assays. Finally, purified p85alpha-/-p85beta+/- c-kit+ cells had a decrease in proliferation in response to kit ligand (kitL), a growth factor important for controlling HSC function in vivo. Collectively, these data identify PI-3K as an important regulator of HSC function and potential therapeutic target in treating leukemic stem cells.
authors.affiliation: Indiana University School of Medicine, Herman B. Wells Center for Pediatric Research, Indianapolis, IN 46202, USA.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Haneline
authors.forename: Hilary
authors.initials: H
authors.lastname: White
authors.forename: Feng-Chun
authors.initials: FC
authors.lastname: Yang
authors.forename: Shi
authors.initials: S
authors.lastname: Chen
authors.forename: Christie
authors.initials: C
authors.lastname: Orschell
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
authors.forename: David A
authors.initials: DA
authors.lastname: Ingram
mesh_terms: D000818:Animals; D002455:Cell Division; D002867:Chromones / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D004261:DNA Replication; D004791:Enzyme Inhibitors; D005838:Genotype; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D008099:Liver / Q000196:embryology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency* / Q000235:genetics*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one