title: The effects of tissue-non-specific alkaline phosphatase gene therapy on craniosynostosis and craniofacial morphology in the FGFR2C342Y/+ mouse model of Crouzon craniosynostosis.
abstract: OBJECTIVE
  Craniosynostosis, the premature fusion of cranial bones, has traditionally been described as a disease of increased bone mineralization. However, multiple mouse models of craniosynostosis display craniosynostosis simultaneously with diminished cranial bone volume and/or density. We propose an alternative hypothesis that craniosynostosis results from abnormal tissue mineralization through the downregulation of tissue-non-specific alkaline phosphatase (TNAP) enzyme downstream of activating mutations in FGFRs.
  
  
  METHODS
  Neonatal Crouzon (FGFRC342Y/+) and wild-type (FGFR+/+) mice were injected with lentivirus to deliver a recombinant form of TNAP. Mice were sacrificed at 4 weeks postnatal. Serum was collected to test for alkaline phosphatase (AP), phosphorus, and calcium levels. Craniofacial bone fusion and morphology were assessed by micro-computed tomography.
  
  
  RESULTS
  Injection with the TNAP lentivirus significantly increased serum AP levels (increased serum AP levels are indicative of efficient transduction and production of the recombinant protein), but results were variable and dependent upon viral lot and the litter of mice injected. Morphological analysis revealed craniofacial form differences for inferior surface (p=0.023) and cranial height (p=0.014) regions between TNAP lentivirus-injected and vehicle-injected Crouzon mice. With each unit increase in AP level, the odds of lambdoid suture fusion decreased by 84.2% and these results came close to statistical significance (p=0.068).
  
  
  CONCLUSIONS
  These results suggest that TNAP deficiency may mediate FGFR2-associated craniosynostosis. Future studies should incorporate injection of recombinant TNAP protein, to avoid potential side effects and variable efficacy of lentiviral gene delivery.
authors: Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI, USA.
authors: E
authors: E
authors: Wang
authors: H K
authors: HK
authors: Nam
authors: J
authors: J
authors: Liu
authors: N E
authors: NE
authors: Hatch
mesh_terms: D000469:Alkaline Phosphatase / Q000097:blood / Q000235:genetics*; D000818:Animals; D002113:Calcification, Physiologic / Q000235:genetics; D002118:Calcium / Q000097:blood; D002508:Cephalometry / Q000379:methods; D003393:Cranial Sutures / Q000254:growth & development / Q000473:pathology; D003398:Craniosynostoses / Q000503:physiopathology / Q000628:therapy*; D003545:Cysteine / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D016086:Lentivirus / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009777:Occipital Bone / Q000254:growth & development / Q000473:pathology; D010294:Parietal Bone / Q000254:growth & development / Q000473:pathology; D010758:Phosphorus / Q000097:blood; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D012886:Skull / Q000254:growth & development / Q000473:pathology*; D014443:Tyrosine / Q000235:genetics; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D010758:Phosphorus; D014443:Tyrosine; C496354:Fgfr2 protein, mouse; D051497:Receptor, Fibroblast Growth Factor, Type 2; C510878:ALPL protein, mouse; D000469:Alkaline Phosphatase; D003545:Cysteine; D002118:Calcium
keywords: bone; craniofacial; craniosynostosis; mineralization; mouse model