Talk:Zone of polarizing activity

ZPA and hedgehog
It looks like someone has altered hedgehog to Sonic Hedgehog in this article. KathyfromNC (talk) 17:49, 2 July 2016 (UTC)

No I'm wrong. The gene is hedgehog for flies and sonic hedgehog for chickens. KathyfromNC (talk) 17:55, 2 July 2016 (UTC)

Formation
Re-entered removed text - needs proper formatting before re-adding. Also to note only one link is necessary. --Iztwoz (talk) 11:49, 31 January 2018 (UTC) The Hox genes, which define features along the anterior-posterior axis of a developing organism, dictate at which points along the axis that limb buds will form. Though limbs emerge at different locations in different species, their positions always correlate with the level of Hox gene expression along the anterior-posterior axis. All limb buds must rely on other signaling factors to obtain their forelimb or hindlimb identity as well; Hox gene expression influences expression of T-box proteins that, in turn, dictate limb identity for certain organisms. In turn, the activation of T-box proteins activates signaling cascades that involve the Wnt signaling pathway and FGF signals. Before limb development begins, T-box proteins initiate FGF10 expression in the proliferating mesenchymal cells of the lateral plate mesoderm, which form the limb bud mesoderm. WNT2B and WNT8C stabilize this FGF10 expression in the forelimb and hindlimb, respectively. This FGF10 expression stimulates WNT3 expression in the above ectodermal cells – resulting in formation of the apical ectodermal ridge (AER) as well as inducing FGF8 expression. The FGF8 secreted by the AER acts to keep the cells of the limb mesenchyme in a mitotically active state and sustains their production of FGF10. This positive feedback loop between the limb mesenchymal cells and the AER maintains the continued growth and development of the entire limb. In addition to limb outgrowth, AER leads to the formation of the ZPA.