In Vivo and In Vitro Expression of Connexins in the Human Corneal Epithelium

Abstract

Gap junction communication in the human corneal epithelium is mediated by Cx26, -30, -31.1, and -43. Poorly differentiated PCECs are uncoupled, and Ca(2+) induced differentiation is associated with an upregulation of connexin expression and intercellular communication. The transfection experiments suggest that KIDS Cx26(D50N) impairs intracellular formation and transport of connexons formed by Cx26 and -30, consistent with a dominant negative effect.

Cx30 exhibits unique characteristics including a long half-life when assembled into gap junctions

“…Evidence for this can be found in skin where Cx30 is expressed in terminally differentiated keratinocytes both in human (Di et al, 2001;Richard, 2003;Churko and Laird, 2013) and murine (Coutinho et al, 2003;Kretz et al, 2003) epidermis, in non-proliferating astrocytes within the brain (Kunzelmann et al, 1999) and retina (Mansour et al, 2013), in cochlear supporting cells (Lowenheim et al, 1999;Chen et al, 2003) and mature lateral wall fibrocytes that have become quiescent. In addition, Cx30 is linked to differentiation of mammary gland cells during lactation (Talhouk et al, 2005) and to calcium-induced differentiation of corneal cells (Shurman et al, 2005). These findings might suggest that long-lived Cx30 plaques are preferentially expressed in quiescent cells or cells undergoing terminal differentiation, perhaps to reduce the burden of constant gap junction renewal and thus permit energy conservation, whilst retaining gap junctional intercellular communication.…”

Expression Pattern of Connexins in the Corneal and Limbal Epithelium of a Primate

“…Our findings in monkey corneal epithelia generally agree with those reported in rabbit and human cornea. 4,17 The most prevalent Cx protein was Cx43. The absence of Cx43 has been used as evidence for identifying limbal stem cells, 18 and Cx43 could be a negative marker to isolate the stem cell-containing population.…”

“…2 Connexins such as Cx26, Cx30, Cx30.1, Cx43, and Cx50 mediate gap junction communication in the cornea of rats, rabbits, and humans. [3][4][5] Most cells express several Cx isoforms in a temporal-, spatial-, and differentiation-specific pattern. For example, epidermal cells express multiple connexins, including Cx26, Cx43, Cx30.3, and Cx31.1.…”

Alternative splice variants of plasma membrane calcium-ATPases in human corneal epithelium

“…Additionally, CE plays a role in dehydration of the underlying stroma and the maintenance of corneal transparency (c.f. (Connon et al 2006;Klyce 1977;Reinach 1985;Shurman et al 2005). CE is a stratified epithelium comprised of morphologically and functionally distinct epithelial cell types that represent stages in a continuum of transitional forms ranging from stem cells to surface epithelial cells (Cenedella and Fleschner 1990;Hanna et al 1961).…”

“…As CE undergoes renewal, there is a constant production of cells that differ in proliferative capacity and differentiated properties and that vary in Ca 2+ -handling properties (Duncan and Collison 2002;Kimura et al 1999). The processes of CE renewal and wound healing involve a coordinated sequence of physiological events including cell migration, proliferation and differentiation (Thoft and Friend 1975), all of which depend on calcium-mediated processes (Cox and Huttenlocher 1998;Hazelton et al 1979;Shurman et al 2005). …”