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Ectopic Anterior Expression of SHH Rescues Tripartite Limb Outgrowth Following Chick Limb Bud Amputation
Author(s) -
Mishima Noboru,
Pira Charmaine,
Uraine Shawn P.,
Oberg Kerby
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a884-d
Subject(s) - zone of polarizing activity , apical ectodermal ridge , sonic hedgehog , limb bud , limb development , fibroblast growth factor , amputation , anatomy , biology , ectopic expression , fgf8 , microbiology and biotechnology , medicine , surgery , embryo , receptor , signal transduction , ectoderm , embryogenesis , gene , genetics
Fibroblast growth factors (FGFs) of the apical ectodermal ridge (AER) and sonic hedgehog (SHH) of the zone of polarizing activity (ZPA) are considered to be driving factors behind limb outgrowth. Distal amputation of the chick wing bud or removal of the AER abates limb outgrowth. Furthermore, expression of SHH within the ZPA ceases following removal of the AER. Exogenous application of FGF to the posterior margin of the limb stump, following distal amputation, reestablishes SHH expression, regenerates amputated tissue and rescues limb outgrowth. However, application of FGF to the anterior margin of the limb stump does not induce SHH and fails to rescue limb outgrowth. Based on these data, we wondered whether SHH rather than AER‐related FGFs might be the critical factor for rescuing limb outgrowth following amputation. To test this hypothesis we used confined micro‐electroporation (CMEP) to ectopically express SHH within the anterior margin of Hamberger‐Hamilton (HH) stage 23 limb stumps following distal (500 μm) amputation. The chicks were harvested at day 10 (HH stage 36) for analysis of skeletal pattern using alcian green staining. Amputation at this stage resulted in truncated wings with only a partial humerus (stylopod). We found that anteriorly expressed SHH alone could induce regeneration and rescue tripartite limb outgrowth (stylopod, zeugopod and autopod). These findings suggest that SHH plays a critical role in tripartite limb outgrowth, while FGFs may play a more supportive role in maintaining the distal location of SHH expression.