Inhibition of Wnt-3a pathway activation by Dkk-1. L cells were transiently transfected with an empty vector (Mock) or with a plasmid encoding Dkk-1 and were either control-treated or purified Wnt-3a-treated for 2 and 4 hours. (a) At both time points cells transfected with the Dkk-1 plasmid fail to induce accumulation of cytoplasmic β-catenin upon Wnt-3a treatment, as detected by Western Blot. In contrast, Mock transfected cells show an elevation in the level of β-catenin upon Wnt-3a treatment. (b) The detection of β-actin served as a loading control. (c) Parallel plates were treated as above and lysates were collected for extraction of total RNA. Dkk-1 mRNA is shown by Northern Blot in the cells transfected with Dkk-1. (d) 18S and 28S rRNA bands are loading controls obtained by acridine orange staining of the gel used for the Northern Blot prior to blotting.