Contributions of placodal and neural crest cells to avian cranial peripheral ganglia

Abstract

The method of embryonic tissue transplantation was used to confirm the dual origin of avian cranial sensory ganglia, to map precise locations of the anlagen of these sensory neurons, and to identify placodal and neural crest-derived neurons within ganglia. Segments of neural crest or strips of presumptive placodal ectoderm were excised from chick embryos and replaced with homologous tissues from quail embryos, whose cells contain a heterochromatin marker. Placode-derived neurons associated with cranial nerves V, VII, IX, and X are located distal to crest-derived neurons. The generally larger, embryonic placodal neurons are found in the distal portions of both lobes of the trigeminal ganglion, and in the geniculate, petrosal and nodose ganglia. Crest-derived neurons are found in the proximal trigeminal ganglion and in the combined proximal ganglion of cranial nerves IX and X. Neurons in the vestibular and acoustic ganglia of cranial nerve VIII derive from placodal ectoderm with the exception of a few neural crest-derived neurons localized to regions within the vestibular ganglion. Schwann sheath cells and satellite cells associated with all these ganglia originate from neural crest. The ganglionic anlagen are arranged in cranial to caudal sequence from the level of the mesencephalon through the third somite. Presumptive placodal ectoderm for the VIIIth, the Vth, and the VIIth, IXth, and Xth ganglia are located in a medial to lateral fashion during early stages of development reflecting, respectively, the dorsolateral, intermediate, and epibranchial positions of these neurogenic placodes.

Maternal diabetes in the rat impairs the formation of neural-crest derived cranial nerve ganglia in the offspring

“…Therefore, this altered ganglionic development represents a specific delay in the development of the cranial nerve ganglia in addition to the more general developmental delay seen in experimental diabetic pregnancy. The main part of the nerve cells and all supporting cells in these ganglia originate from the neural crest, the remaining neurons are derived from ectodermal placodes [17]. Studies in avian embryos indicate that the neural crest cells form mainly the proximal parts of the cranial nerve ganglia [17].…”

“…This method has been used to investigate the toxicity of ethanol [15] and valproic acid [16] in mouse embryo development. The neurons of the cranial nerve ganglia V, IX and X originate mainly from different parts of the neural crest, whereas the neurons of ganglia VII, VIII mainly comes from the epidermal placodes with some contribution from the neural crest [17].…”

Asymmetric expression of a novel homeobox gene in vertebrate sensory organs

“…At this stage, the expression of SOHo-delineated the nonneurogenic region of the otic pit on the lateral posterior half. The negative regions are fated to become sensory end organs as well as neurons of the VIIIth cranial ganglion (Knowlton, 1967;D'Amico and Noden, 1983). This would suggest that the SOHoexpression seen later in the VIIIth cranial ganglion, by stage 23, reflects transcriptional activation after the cells have migrated from the otic pit and associated to form a ganglion.…”

Expression of Hox 2.1 protein in restricted populations of neural crest cells and pharyngeal ectoderm

“…Also, according to D'Amico-Martel and Noden (1983), the nodose placode releases neuroblasts to the ganglion primordium during stages 19 and 20 in the chick em- Lateral view of the stage 19 (4 days) chick embryo stained with EIC8 which specifically recognizes neurons and the circumpharyngeal crest, a subpopulation of the vagal crest cells. This specimen shows the peripheral nervous system as well as the arch-shaped mesenchymal cell mass of the circumpharyngeal crest.…”