title: The impact of coexisting genetic mutations on murine optic glioma biology.
abstract: BACKGROUND
  Children with the neurofibromatosis type 1 (NF1) tumor predisposition syndrome are prone to the development of optic pathway gliomas resulting from biallelic inactivation of the NF1 gene. Recent studies have revealed the presence of other molecular alterations in a small portion of these NF1-associated brain tumors. The purpose of this study was to leverage Nf1 genetically engineered mouse strains to define the functional significance of these changes to optic glioma biology.
  
  
  METHODS
  Nf1+/- mice were intercrossed with Nf1(flox/flox) mice, which were then crossed with Nf1(flox/flox); GFAP-Cre mice, to generate Nf1(flox/mut); GFAP-Cre (FMC) mice. These mice were additionally mated with conditional KIAA1549:BRAF knock-in or Pten(flox/wt) mice to generate Nf1(flox/mut); f-BRAF; GFAP-Cre (FMBC) mice or Nf1(flox/mut); Pten(flox/wt); GFAP-Cre (FMPC) mice, respectively. The resulting optic gliomas were analyzed for changes in tumor volume, proliferation, and retinal ganglion cell loss.
  
  
  RESULTS
  While KIAA1549:BRAF conferred no additional biological properties on Nf1 optic glioma, FMPC mice had larger optic gliomas with greater proliferative indices and microglial infiltration. In addition, all 3 Nf1 murine optic glioma strains exhibited reduced retinal ganglion cell survival and numbers; however, FMPC mice had greater retinal nerve fiber layer thinning near the optic head relative to FMC and FMBC mice.
  
  
  CONCLUSIONS
  Collectively, these experiments demonstrate genetic cooperativity between Nf1 loss and Pten heterozygosity relevant to optic glioma biology and further underscore the value of employing genetically engineered mouse strains to define the contribution of discovered molecular alterations to brain tumor pathogenesis.
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Aparna
authors.initials: A
authors.lastname: Kaul
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Toonen
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Gianino
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, Missouri.
authors.forename: David H
authors.initials: DH
authors.lastname: Gutmann
mesh_terms: D000818:Animals; D016923:Cell Death; D004195:Disease Models, Animal; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D009456:Neurofibromatosis 1 / Q000235:genetics*; D020339:Optic Nerve Glioma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019574:Optic Nerve Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051059:PTEN Phosphohydrolase / Q000235:genetics; D012165:Retinal Ganglion Cells / Q000473:pathology; D015398:Signal Transduction
chemical_list: D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse
keywords: BRAF; PTEN; neurofibromatosis; neurofibromin; pediatric brain tumor