Gene expression analysis during the induction and patterning of the conjunctival papillae in the chick embryonic eye

The induction and patterning of the conjunctival papillae (i.e. epithelial thickenings of the conjunctiva required for the induction of the underlying, neural crest-derived scleral ossicles) is complex. It takes place over a period of two days and follows a defined spatiotemporal sequence. In this study, we investigated the spatial and temporal expression pattern of four genes over seven morphological stages of development of these papillae. We show that β-catenin is expressed during the pre-patterning of the epithelium prior to papilla induction and second that β-catenin, Ednrb and Inhba are expressed during the induction and patterning of the conjunctival papillae. Furthermore, we identified two genes, β-catenin and Prox1, that may be involved in the induction of the underlying scleral bones. These data provide an excellent baseline for future studies, setting the stage for functional studies aimed at examining the role of these genes in the patterning of the scleral ossicle system. This study also outlines the similarities between the conjunctival papillae and other placodes and may provide insights into the evolution and development of the conjunctival papillae.