title: Biphasic fusion of the murine posterior frontal suture.
abstract: BACKGROUND
  Craniosynostosis is the premature fusion of cranial sutures early in development. Mice are commonly used to study the mechanisms driving both normal and pathologic cranial suture development. Despite their frequency of use as a model, the time course of bone formation and mineralization during fusion of mouse posterior frontal suture is not well defined.
  
  
  METHODS
  To address this, C57Bl/6J mice were euthanized at ages ranging from 6 to 107 days, and the posterior frontal sutures were imaged using micro-computed tomography. Scans were analyzed with an image-processing algorithm that was previously validated with serial histology to quantify both suture fusion and mineral content. The expression profile of genes associated with key developmental time points was examined using real-time polymerase chain reaction in both the bone and the dura.
  
  
  RESULTS
  Results demonstrate that the bones of the posterior frontal suture come together during days 10 to 20 and then increase in mineral content and volume between days 21 and 45. The onset of posterior frontal suture fusion was associated with an increase in cartilage-associated genes on day 12. Later mineralization of the suture was associated with an increase in mRNAs for osteoblast differentiation markers, bone morphogenetic proteins, and bone morphogenetic protein inhibitors.
  
  
  CONCLUSIONS
  Complete analysis fusion posterior frontal suture shows that it occurs in a discontinuous biphasic manner. The first phase is from days 10 to 20 and involves production of cartilage. A second mineralization phase from days 21 to 45 was seen with both the imaging algorithm and changes in gene expression.
authors.affiliation: Atlanta, Ga. From the Petit Institute for Bioengineering and Bioscience, the Wallace H. Coulter Department of Biomedical Engineering, and the Woodruff School of Mechanical Engineering, Georgia Institute of Technology; Emory University School of Medicine; and Children's Healthcare of Atlanta.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Hermann
authors.forename: Megan A
authors.initials: MA
authors.lastname: Richards
authors.forename: Regina
authors.initials: R
authors.lastname: Chang
authors.forename: Rene
authors.initials: R
authors.lastname: Olivares-Navarrete
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Williams
authors.forename: Robert E
authors.initials: RE
authors.lastname: Guldberg
authors.forename: Brani
authors.initials: B
authors.lastname: Vidakovic
authors.forename: Zvi
authors.initials: Z
authors.lastname: Schwartz
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Boyan
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D003393:Cranial Sutures / Q000254:growth & development*; D005624:Frontal Bone / Q000254:growth & development*; D015870:Gene Expression; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D060888:Real-Time Polymerase Chain Reaction
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