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]. [ ]

This is just here as a test because I lose it

Term information

database cross reference


axiom lost from external ontology

relationship loss: subclass proliferative region (TAO:0000098)[TAO]

curator note

note that media, dorsal fins etc have AERs.

depicted by

external definition

Distal ectodermal thickening which forms along the anterior-posterior limb axis. Signaling from this region influences proximal-distal patterning of the limb. Structure is missing in some lineages (salamanders, Eleutherodactylus coqui) however morphologically their indistinct distal ectoderm may still be involved in signaling.[AAO]
Proliferative region that is part of the developing fin fold or fin.[TAO]

function notes

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

has exact synonym

apical epidermal ridge

has related synonym

crista ectodermalis apicalis



taxon notes

The AER of tetrapods regresses after specification of skeletal progenitors, the AER of teleosts form an elongating fin fold