Fig. 10

Blockage of cell proliferation results in the normalization of epidermal hyperplasia, whereas blockage of Mmp9 activity reduces epidermal invasiveness in psoriasis mutants.

(a-b).Confocal images of GFP in the tail fin of live 48 hpf atp1b1a morphant Tg(NFκB-RE:eGFP) transgenics, showing that elevated NFκB activity in atp1b1a morphants (a) is not reduced by hydroxyurea treatment (b). For quantification, see Figure 10-figure supplement 1. (c-d) mmp9 WISH of 54 hpf psoriasis mutants raised in hypotonic E3. Elevated mmp9 expression in mutant epidermis (c) is not reduced by hydroxyurea (HU) treatment (d). (e) Quantification of the phenotypes of psoriasis mutants, either treated with 50 mM hydroxyurea or injected with mmp9 MO, compared to their respective siblings. e, pericardial edema; wa, weak epidermal aggregates; ma, medium epidermal aggregates; sa, strong epidermal aggregates . n = 17-47. Similar results for each condition were obtained in two additional independent experiments. (f-g) mmp9 knockdown alleviates basement membrane fragmentation. Laminin IF, counterstained with DAPI, in psoriasis mutants at 58 hpf, epidermal aggregates of comparable sizes. In the un-injected psoriaris mutant (f), the aggregate is associated with BM fragmentation, while the underlying BM is largely intact in the psoriasis mutant injected with mmp9 MO (g). For more images and numbers, see Figure 10-figure supplement 2. (h) mmp9 knockdown alleviates epidermal invasiveness. Laminin and p63 IF of transverse sections, counterstained with DAPI, through the yolk sac of a psoriasis mutant (58 hpf) injected with mmp9 MO. The basement membrane is largely intact (arrowhead to small remaining region with thinner basement membrane), and p63 keratinocytes are confined to the epidermal compartment above the basement membrane. For un-injected mutant and wt controls, see Figure 2i,j. (i) Diagram of the identified pathway in which the two required non-cell-autonomous effects caused by loss of Atp1b1a in periderm and osmoregulatory organs converge in basal cells. The pathway subsequently diverges downstream of NFκB to mediate overgrowth versus invasiveness of transformed keratinocytes. Question marks indicate components that have not yet been identified. For details, see text.