Neuron-specific enolase expression during eye development in the chicken embryo.

Neuron-specific enolase has been used by others as a marker for the identification of cells of presumed neural crest origin in the human eye. The contributions of neural crest to the ocular tissues have been studied most definitively in the chicken embryo. The developing chicken eye was therefore chosen to further investigate the usefulness of neuron-specific enolase as a neural crest marker. Chicken embryos of various development stages were processed for the immunohistochemical localization of neuron-specific enolase with two different specific antisera. The nerve fiber layer of the neural retina and the optic nerve reacted positively. The first weak staining was found at day 10; it became rapidly stronger during the next 2 days. A positive reaction was also observed in the ciliary ganglion. In contrast, no staining was found in tissues of known neural crest origin. Cornea, sclera, trabecular tissues and iris stroma remained negative throughout the developmental stages studied. Therefore, neuron-specific enolase can not be used as a reliable marker of neural crest derived cells, at least in the chicken embryo. Unexpectedly the lens epithelium showed moderate neuron-specific enolase activity beginning on day 5. alpha-Enolase is an important crystallin in the lens of some species, particularly the turtle. It has also been demonstrated to be present in the chicken lens in a fairly high concentration. It is possible, that neuron-specific or gamma-enolase has a similar role in the chicken lens.