title: Inhibition of histone deacetylases by Trichostatin A leads to a HoxB4-independent increase of hematopoietic progenitor/stem cell frequencies as a result of selective survival.
abstract: BACKGROUND
  DNA and chromatin modifications are critical mediators in the establishment and maintenance of cell type-specific gene expression patterns that constitute cellular identities. One type of modification, the acetylation and deacetylation of histones, occurs reversibly on lysine ε-NH₃(+) groups of core histones via histone acetyl transferases (HAT) and histone deacetylases (HDAC). Hyperacetylated histones are associated with active chromatin domains, whereas hypoacetylated histones are enriched in non-transcribed loci.
  
  
  METHODS
  We analyzed global histone H4 acetylation and HDAC activity levels in mature lineage marker-positive (Lin(+)) and progenitor lineage marker-negative (Lin⁻) hematopoietic cells from murine bone marrow (BM). In addition, we studied the effects of HDAC inhibition on hematopoietic progenitor/stem cell (HPSC) frequencies, cell survival, differentiation and HoxB4 dependence.
  
  
  RESULTS
  We observed that Lin⁻ and Lin(+) cells do not differ in global histone H4 acetylation but in HDAC activity levels. Further, we saw that augmented histone acetylation achieved by transient Trichostatin A (TSA) treatment increased the frequency of cells with HPSC immunophenotype and function in the heterogeneous pool of BM cells. Induction of histone hyperacetylation in differentiated BM cells was detrimental, as evidenced by preferential death of mature BM cells upon HDAC inhibition. Finally, TSA treatment of BM cells from HoxB4(-/-) mice revealed that the HDAC inhibitor-mediated increase in HPSC frequencies was independent of HoxB4.
  
  
  CONCLUSIONS
  Overall, these data indicate the potential of chromatin modifications for the regulation of HPSC. Chromatin-modifying agents may provide potential strategies for ex vivo expansion of HPSC.
authors.affiliation: Institut f&#x00FC;r Medizinische Strahlenkunde und Zellforschung (MSZ), Universit&#x00E4;t W&#x00FC;rzburg, W&#x00FC;rzburg, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Obier
authors.forename: Christoph F
authors.initials: CF
authors.lastname: Uhlemann
authors.forename: Albrecht M
authors.initials: AM
authors.lastname: Müller
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D019070:Cell Lineage; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D006410:Hematopoiesis / Q000187:drug effects / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics; D006877:Hydroxamic Acids / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D014157:Transcription Factors / Q000235:genetics
chemical_list: D000943:Antigens, Differentiation; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; D006877:Hydroxamic Acids; D014157:Transcription Factors; C012589:trichostatin A; D006655:Histone Deacetylases