Innexins in the wing disc and innexin-overexpression effects on wingless.
A-C, wing discs from wandering third instar larvae of genotype C96GAL4 / UAS-mCD8::GFP.L. The C96GAL4 line directs reporter expression in cells of the wing margin (green). Discs have been antibody-stained using the relevant rabbit polyclonal primary antibody to detect Inx2 protein (A, red), Inx3 protein (B, blue) and Ogre protein (C, yellow). The expression pattern of each of these innexin subunits looks broadly similar in wing discs. All are expressed in the wing pouch and Inx2 and Inx3 are also expressed in peripodial cells. Wingless protein is expressed in the wing margin (D, mauve - the same cells that express GFP under C96GAL4 control in A-C), however, its expression is severely reduced when a strong allele of UAS-ogre is directed to the margin using the C96GAL4 line (E, mauve). In the embryonic proventriculus, Inx2 promotes the expression of wingless (...and hedgehog and delta - Lechner et al, 2007). Ogre appears to have the opposite effect on wingless expression in wing discs, although we don't know if this is due to gap junction activity or secondary/artefactual effects (for example, overexpression of UAS-inx2 can cause a significant increase in cell death in the embryo Bauer et al, 2004).