Neural crest derivatives in ocular and periocular structures

Abstract

In vertebrates, the eye is an ectodermal compound structure associating neurectodermal and placodal anlagen. In addition, it benefits early on from a mesenchymal ectoderm-derived component, the neural crest. In this respect, the construction of chimeras between quail and chick has been a turning point, instrumental in appraising the contribution of the cephalic neural crest to the development of ocular and periocular structures. Given the variety of crest derivatives underscored in the developing eye, this study illustrates the fascinating ability of this unique structure to finely adapt its differentiation to microenvironmental cues. This analysis of neural crest cell contribution to ocular development emphasizes their paramount role to design the anterior segment of the eye, supply refracting media and contribute to the homeostasy of the anterior optic chamber.

The differentiation and morphogenesis of craniofacial muscles

“…17). These populations of myogenic cells, often already including multinucleated myotubes (Wahl et al, 1994), move en masse into neural crest-occupied periocular territories (Wahl and Noden, 1997;Creuzet et al, 2005). Migration of single cells does not occur and these myoblasts do not express the c-Met receptor.…”

Skeletal elements in the vertebrate eye and adnexa: Morphological and developmental perspectives

“…In the domestic chicken, streams of neural crest (NC) cells from the posterior diencephalon, the mesencephalon, and the first two rhombomeres of the metencephalon converge on the optic vesicle where they overlap one another extensively (Creuzet et al, 2005). This territory of NC cells corresponds to the cephalic domain of the neural fold that gives rise to the entire facial skeleton and, hence, also the skeletal elements of the ocular region.…”

“…Removal of the mesencephalic NC of chicken embryos at the five-to six-somite stage (HH stage 8.5) results in embryos without a sclera or a scleral cartilage cup and, therefore, deformed eyes . When this experiment is performed earlier at the three-to four-somite stage (HH stage 7.5-8), the result is cyclopia (only one eye develops in the middle of the face) (Etchevers et al, 1999), indicating the existence of a transient crest-dependent molecular requirement (Creuzet et al, 2005). For normal scleral development, a minimum of a third of the cranial NC domain is required .…”

“…Although it is not clear which stream(s) gives rise to the other ocular skeletal elements, most if not all appear to be NC derivatives. For example, among the adnexal elements, circumorbital bones are part of the NC derived dermatocranium, and eyelids and nictitating membranes develop from NC mesenchyme (ectomesenchyme; Creuzet et al, 2005). Thus, the NC provides the skeletal support for ocular structures.…”

Stem cells of the adult cornea: From cytometric markers to therapeutic applications

“…At this stage, it consists of a twolayered epithelium that is separated from the endothelium by an acellular space, the so called primary stroma (3). Studies of chick embryos proved that the corneal stroma and endothelium originates from neural crest derived mesenchymal cells (4), however, morphogenesis of the mesenchyma-derived tissues in the human cornea is not clear yet. In situ formation from mesenchymal tissue (5,6), as well as a three wave migration of neural crest cells giving rise to the iris, corneal endothelium and stromal keratocytes (2,7) have been proposed.…”