The preplacodal region: an ectodermal domain with multipotential progenitors that contribute to sense organs and cranial sensory ganglia

Abstract

The otic primordium belongs to a group of related structures, the sensory placodes that contribute to the paired sense organs -ear, eye and olfactory epithelium -and to the distal parts of the cranial sensory ganglia. Recent evidence suggests that despite their diversity, all placodes share a common developmental origin and a common molecular mechanism which initiates their formation. At the base of placode induction lies the specification of a unique "placode field", termed the preplacodal region and acquisition of this "preplacodal state" is required for ectodermal cells to undergo otic development. Here I review the molecular mechanisms that sequentially subdivide the ectoderm to give rise to the placode territory.

Early development of the nervous system of the eutherian <i>Tupaia belangeri</i>

“…(neurogenic) placodes which segregate from the U-shaped panplacodal primordium (Streit, 2007;Schlosser, 2010;Saint-Jeannet and Moody, 2014). This hypothesis could be fully confirmed on the example of the trigeminal placode (Obermayer, 2009;Knabe et al, 2009: Fig.…”

Molecular analysis of neurogenic placode development in a basal ray‐finned fish

“…All cranial placodes originate from a common ''pre-placodal region'' or ''pan-placodal primordium'' (Schlosser, 2010;Streit, 2007), i.e., a crescent of ectoderm around the anterior neural plate characterized by expression of members of the Eya, Six1/2, and Six4/5 families of transcription factors or co-factors, whose expression is maintained in all cranial placodes and their derivatives (reviewed by Schlosser, 2010;Streit, 2007). An explosion of molecular information and functional experiments over the past decade has greatly increased our understanding of the mechanisms underlying the induction of the preplacodal region itself, its subsequent regionalization, and the formation of individual placodes and their derivatives (reviewed by Ladher et al, 2010;Schlosser, 2010;Streit, 2007).…”

Early development of the facial nerve in human embryos at stages 13–15

“…The facial and vestibulocochlear ganglia develop from the facial and otic crest opposite neuromere 4 and 5. The trigeminal, facial, glossopharyngeal and vagal ganglia develop from the neural crest and epipharyngeal placode [10,11,38] which are a part of the ectodermal ring and appear at stage 12 [23].…”