title: Gene expression in BMPR2 mutation carriers with and without evidence of pulmonary arterial hypertension suggests pathways relevant to disease penetrance.
abstract: BACKGROUND
  While BMPR2 mutation strongly predisposes to pulmonary arterial hypertension (PAH), only 20% of mutation carriers develop clinical disease. This finding suggests that modifier genes contribute to FPAH clinical expression. Since modifiers are likely to be common alleles, this problem is not tractable by traditional genetic approaches. Furthermore, examination of gene expression is complicated by confounding effects attributable to drugs and the disease process itself.
  
  
  METHODS
  To resolve these problems, B-cells were isolated, EBV-immortalized, and cultured from familial PAH patients with BMPR2 mutations, mutation positive but disease-free family members, and family members without mutation. This allows examination of differences in gene expression without drug or disease-related effects. These differences were assayed by Affymetrix array, with follow-up by quantitative RT-PCR and additional statistical analyses.
  
  
  RESULTS
  By gene array, we found consistent alterations in multiple pathways with known relationship to PAH, including actin organization, immune function, calcium balance, growth, and apoptosis. Selected genes were verified by quantitative RT-PCR using a larger sample set. One of these, CYP1B1, had tenfold lower expression than control groups in female but not male PAH patients. Analysis of overrepresented gene ontology groups suggests that risk of disease correlates with alterations in pathways more strongly than with any specific gene within those pathways.
  
  
  CONCLUSIONS
  Disease status in BMPR2 mutation carriers was correlated with alterations in proliferation, GTP signaling, and stress response pathway expression. The estrogen metabolizing gene CYP1B1 is a strong candidate as a modifier gene in female PAH patients.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA. j.west@vanderbilt.edu
authors.forename: James
authors.initials: J
authors.lastname: West
authors.forename: Joy
authors.initials: J
authors.lastname: Cogan
authors.forename: Mark
authors.initials: M
authors.lastname: Geraci
authors.forename: Linda
authors.initials: L
authors.lastname: Robinson
authors.forename: John
authors.initials: J
authors.lastname: Newman
authors.forename: John A
authors.initials: JA
authors.lastname: Phillips
authors.forename: Kirk
authors.initials: K
authors.lastname: Lane
authors.forename: Barbara
authors.initials: B
authors.lastname: Meyrick
authors.forename: Jim
authors.initials: J
authors.lastname: Loyd