title: Chicken wings and the brachial plexus.
abstract: OBJECTIVE
  Some stages of limb development can now be described in terms of gene sequences and functions. This paper reports on the development of the brachial plexus (BP) in the chick. It also presents a short review on the principles of the peripheral nerve outgrowth.
  
  
  METHODS
  The early development of the brachial plexus of chicken embryos is mapped using immunohistochemistry. This is then analysed in relation to the expression pattern of an axonal guidance gene, Semaphorin3a, by in situ hybridization studies.
  
  
  RESULTS
  The motor axons that innervate the chick wing emerge from the spinal cord in spinal nerves 12-17. These axons grow towards the developing limb and then congregate at its base to form the plexus. In response to unknown cues, these axons rearrange, before emerging in the defined nerve trunks that innervate the limb. The developmental stages of BP morphogenesis described here closely correlate with previous reports with a significant difference of a shorter 'waiting period'.
  
  
  CONCLUSIONS
  The development of the brachial plexus is now better understood. The waiting period, with more modern techniques, is observed to be shorter than previously reported. The significance of this and the role of the guidance molecule, Semaphorin3a, in this process, are being investigated and the results may have important implications on the management of brachial plexus palsy and other peripheral nerve lesions.
authors.affiliation: Department of Embryology, Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia. tdieu@plasticsurg.com.au
authors.forename: Tam
authors.initials: T
authors.lastname: Dieu
authors.forename: Don
authors.initials: D
authors.lastname: Newgreen
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D001917:Brachial Plexus / Q000196:embryology*; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D009046:Motor Neurons / Q000166:cytology; D039961:Semaphorins / Q000378:metabolism; D014921:Wings, Animal / Q000196:embryology*
chemical_list: D039961:Semaphorins