Expression of semaphorin 3A and its receptors during mouse corneal development

Semaphorin 3A (Sema3A) functions to guide the growth of neurons during development, with its effects being mediated by receptor complexes composed of neuropilin (Npn) and plexin (Plx) proteins. We have now examined the expression of Sema3A and its receptor components Npn1 and PlxA during development of the mouse cornea. Sema3A and Npn1 showed similar patterns of expression by immunohistofluorescence analysis, with such expression being prominent in the corneal epithelium during both embryonic and postnatal development. In contrast, PlxA was not expressed in the corneal epithelium until after eye opening between postnatal days 12 and 14. Laser capture microdissection followed by reverse transcription and polymerase chain reaction analysis also showed that the abundance of PlxA mRNA in corneal epithelial cells increased significantly during postnatal development, again in association with eye opening. Given that atmospheric oxygen is thought to play a role in corneal epithelial differentiation and maintenance, our results suggest that the up-regulation of PlxA expression in the corneal epithelium during postnatal development is triggered by exposure of the cornea to the atmosphere. Furthermore, the newly expressed PlxA may contribute to the differentiation of corneal epithelial cells by mediating Sema3A signaling.

Research highlights
► Eye opening and consequent exposure of the corneal surface to the atmosphere is very important events for corneal development.
► The epithelial cell differentiation in the cornea is thought to be regulated by exposure to the atmosphere.
► The neuronal guidance protein, semaphorin3A plays a role for the differentiation of corneal epithelial cells.
► Exposure to the atmosphere may trigger expression of PlxA in the corneal epithelium and the newly expressed PlxA may contribute to corneal epithelial cell differentiation by mediating Sema3A signaling.