title: Developmentally regulated expression of Sema3A chemorepellant in the developing mouse incisor.
abstract: OBJECTIVE
  Semaphorin 3A (Sema3A) is an essential chemorepellant controlling peripheral axon pathfinding and patterning, but also serves non-neuronal cellular functions. Incisors of rodent are distinctive from molars as they erupt continuously, have only one root and enamel is present only on the labial side. The aim of this study is to address putative regulatory roles of Sema3A chemorepellant in the development of incisor innervation and formation.
  
  
  METHODS
  This study analyzed expression of Sema3A mRNAs during embryonic and early post-natal stages of mouse mandibular incisor using sectional radioactive in situ hybridization.
  
  
  RESULTS
  Although Sema3A mRNAs were observed in condensed dental mesenchyme during the early bud stage, they were absent in dental papilla or pulp at later stages. Sema3A mRNAs were observed in the dental epithelium including the cervical loops and a prominent expression was also seen in alveolar bone. Interestingly, transcripts were absent from the mesenchymal dental follicle target area (future periodontal ligament) throughout the studied stages.
  
  
  CONCLUSIONS
  The expression patterns of Sema3A indicate that it may control the timing and patterning of the incisor innervation. In particular, Sema3A appears to regulate innervation of the periodontal ligament, while nerve penetration into the incisor dental pulp appears not to be dependent on Sema3A. Moreover, Sema3A may regulate the functions of cervical loops and the development of alveolar bone. Future study with Sema3A deficient mice will help to elucidate the putative neuronal and non-neuronal functions of Sema3A in incisor tooth development.
authors.affiliation: Department of Biomedicine, University of Bergen, Norway.
authors.forename: Kyaw
authors.initials: K
authors.lastname: Moe
authors.forename: Anjana
authors.initials: A
authors.lastname: Shrestha
authors.forename: Inger Hals
authors.initials: IH
authors.lastname: Kvinnsland
authors.forename: Keijo
authors.initials: K
authors.lastname: Luukko
authors.forename: Päivi
authors.initials: P
authors.lastname: Kettunen
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D003782:Dental Pulp / Q000196:embryology* / Q000294:innervation; D018507:Gene Expression Regulation, Developmental; D007180:Incisor / Q000196:embryology / Q000378:metabolism*; D008334:Mandible; D051379:Mice; D009805:Odontogenesis / Q000502:physiology*; D010513:Periodontal Ligament / Q000196:embryology / Q000294:innervation*; D012333:RNA, Messenger / Q000032:analysis; D040121:Semaphorin-3A / Q000235:genetics / Q000378:metabolism*; D014083:Tooth Germ / Q000196:embryology / Q000294:innervation; D014276:Trigeminal Nerve / Q000196:embryology / Q000502:physiology
chemical_list: D012333:RNA, Messenger; C488217:Sema3a protein, mouse; D040121:Semaphorin-3A