Multilayered ectodermal region at the distal tip of a limb or fin bud necessary for the proper development of the underlying mesenchyme[MP,modified]. Along with the zone of polarizing activity, it is a crucial organizing region during limb development[WP].
Comment:
[function-note] "maintaining mesenchyme in plastic proliferating state; maintaining expression of A-P axis genes; interacting with D-V proteins. Genes: AER induced by Fgf10 in mesenchyme. AER secretes Fgf8, which stimulates mitosis in the mesenchyme causing Fgf10 production - positive feedback loop"; [taxon-note] "The AER of tetrapods regresses after specification of skeletal progenitors, the AER of teleosts form an elongating fin fold" xsd:string {source="PMID:20574421"}