Figure 5. Wnt signaling expands the number of Isl-1–positive progenitors in AHF explants.

(A–C) The AHF was explanted as shown (A) and cultured for 2 days in the absence (B) or presence (C) of Wnt3a. Isl-1 immunostaining increased upon treatment with Wnt3a. (D) Isl-1–positive cells increased approximately 50% in Wnt3a-treated explants. (E) Isl-1 mRNA expression also increased, as determined by Q-PCR. To determine whether this increase was due to an increase in Isl-1 expression per cell or due primarily to an increase in Isl-1–positive cells, explants were treated with HUA to inhibit cell proliferation. HUA treatment inhibited the increase in Isl-1 mRNA expression, which suggests that the majority of increased Isl-1 immunostaining and mRNA expression was the result of expansion of Isl-1–positive cells after Wnt3a treatment. **P < 0.005.