FIG. 3.

Cardiac differentiation of DMZ tissue. DMZ explants were cultured for 4 days in the (A–C) presence or (D) absence of 20 ng/mL WNT1 and immunostained for sarcomeric myosin heavy chain. (A, B) Brightfield and fluorescent images of an individual WNT1-treated explant that displayed sarcomeric myosin immunoreactivity. (C) Another example of an explant incubated with WNT1 exhibiting cardiac tissue that stained positive for sarcomeric myosin. A comparison of the WNT1-treated tissue with (D) nontreated control DMZ demonstrates that ectopic canonical WNT signaling did not alter the pattern of sarcomeric myosin expression within the tissue. (E, F) In contrast, cardiac differentiation of the DMZ tissue was blocked by exposure of DMZ explants to 50 μM LY294002, which inhibits signaling via phosphatidylinositol 3-kinase, as shown for an individual explant imaged by brightfield and fluorescent microscopy. Scale bars=100 μm.