title: Kit and Scl regulation of hematopoietic stem cells.
abstract: OBJECTIVE
  KIT tyrosine kinase receptor is essential for several tissue stem cells, especially for hematopoietic stem cells (HSCs). Moderately decreased KIT signaling is well known to cause anemia and defective HSC self-renewal, whereas gain-of-function mutations are infrequently found in leukemias. Thus, maintaining KIT signal strength is critically important for homeostasis. KIT signaling in HSCs involves effectors such as SHP2 and PTPN11. This review summarizes the recent developments on the novel mechanisms regulating or reinforcing KIT signal strength in HSCs and its perturbation in polycythemia vera.
  
  
  RESULTS
  Stem cell leukemia (SCL) is a transcription factor that is essential for HSC development. Genetic experiments indicate that Kit, protein tyrosine phosphatase, nonreceptor type 11 (Ptpn11), or Scl control long-term HSC self-renewal, survival, and quiescence in adults. Kit is now shown to be centrally involved in two feedforward loops in HSCs, one with Ptpn11 and the other with Scl.
  
  
  CONCLUSIONS
  Knowledge of the regulatory mechanisms that favor self-renewal divisions or a lineage determination process is central to the design of strategies to expand HSCs for the purpose of cell therapy. In addition, transcriptome and phosphoproteome analyses of erythroblasts in polycythemia vera identified lower SCL expression and hypophosphorylated KIT, suggesting that the KIT-SCL loop is relevant to the pathophysiology of human blood disorders as well.
authors.affiliation: aInstitute of Research in Immunology and Cancer, University of Montreal bMolecular Biology Program, Faculty of Medicine, University of Montreal cInstitut de Recherches Cliniques de Montreal (IRCM) dDepartment of Biochemistry eDepartment of Pharmacology, Faculty of Medicine, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Shanti
authors.initials: S
authors.lastname: Rojas-Sutterlin
authors.forename: Eric
authors.initials: E
authors.lastname: Lecuyer
authors.forename: Trang
authors.initials: T
authors.lastname: Hoang
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation; D002470:Cell Survival / Q000235:genetics; D004843:Epistasis, Genetic; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology*; D006801:Humans; D011401:Promoter Regions, Genetic; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism*; D019089:Stem Cell Factor / Q000235:genetics / Q000378:metabolism; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D015533:Transcriptional Activation
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D011518:Proto-Oncogene Proteins; D019009:Proto-Oncogene Proteins c-kit; D019089:Stem Cell Factor; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; C067143:TAL1 protein, human