alpha 9 and beta 8 integrin expression correlates with the merger of the developing mouse eyelids

As previously reported, alpha 9 integrin is expresses between the merged or fused eyelids of mice at birth, and changes in alpha 9 localization occur during lid opening. To determine whether alpha 9 and/or additional integrin subunits mediate the emergence and temporary fusion of the eyelids, immuno fluorescence and confocal microscopy were used to evaluate the localization of various integrin subunits in the developing ocular surface of the mouse . No detectable beta 5, beta 6, or beta 7 integrins were observed on the ep ithelia of the ocular surface. alpha 2, alpha 3, alpha v, and beta 1 integr ins were most abundant in the basal cells beginning at 13.5 days post conce ption and remained primarily localized to the basal cell layers throughout development. beta 4 was localized at the basal surface of the epidermal bas al cells beginning at 13.5 days post conception but was not found on the co rneal epithelial basal cells until after birth. alpha 9 and beta 8 integrin s were present on suprabasal cells of the epidermis at the leading edge of the eyelid before merger and on the epithelial bridge that forms immediatel y after these tissues merge, suggesting that they play a role in the initia l fusion of the epithelial tissues of the eyelid and in stabilizing the epi thelial junction, After birth and into adulthood, beta 8 was retained withi n the suprabasal cell layers of the epidermis, whereas alpha 9 became local ized to the basal cells of the epidermis, the conjunctiva, and the limbus, The lack of co-localization of beta 4 with either alpha 9 or beta 8 in doub le-labeling studies suggests that alpha 9 and beta 8 are restricted to the lateral and apical aspects of those cells in which they are expressed. The presence of tenascin-C and laminin-5 at the epithelial junction site sugges ts that alpha 9: tenascin-C and beta 4: laminin-5 interactions may play a r ole in stabilizing the fusion between lids early on but do not appear to be involved in the movement of the lids across the cornea. The data presented identify specific integrins and matrix proteins that are likely to mediate eyelid fusion. Dev Dyn 1999;214:216-228. (C) 1999 Wiley-Liss, Inc.