Fig. 3. Reversible action of inhibitory Wnt proteins on satellite-cell proliferation. Quantification of satellite-cell progeny on fibres cultured in two consecutive 36 hour stages. Fibres cultured for 36 hours in Wnt6 and then transferred to another dish of Wnt6-expressing cells for an additional 36 hours gave significantly lower number of satellite-cell progeny compared with control (^*P<0.02). Fibres cultured initially with control cells and then transferred to Wnt6-expressing cells gave fewer progeny than fibres cultured in control cells alone (although this was not statistically significant). Fibres cultured in Wnt6 and then transferred to Wnt1-expressing cells gave significantly more progeny compared with fibres cultured in Wnt6 alone (P<0.005) or those in control or Wnt6-expressing cell conditions (P<0.05). Fibres cultured in control cells and then transferred to Wnt1 (control-Wnt1) gave significantly more satellite-cell progeny compared with Wnt6-Wnt1 (^*P<0.02), control-Wnt6 (P<0.00001), Wnt6-Wnt6 (P<0.00001) and control-control (^¶P<0.001). (B) Myogenic profiling after two consecutive 36 hour periods with control cells gave medium-sized clusters that either expressed myogenin (red arrowhead) or nuclear Pax7 (green arrowhead). (C) Profiling after incubation with control cells followed by Wnt1 cells gave rise to large clusters that predominantly expressed Pax7 (green arrowhead) with a minority of myogenin-positive cells (red arrowhead). (D) Incubation of fibres in two consecutive periods with Wnt6 gave small clusters of myogenic progeny expressing either myogenin (red arrowhead) or Pax7 (green arrowhead).