AKT Signaling Mediates IGF-I Survival Actions on Otic Neural Progenitors
Figure 5
IGF-I protects otic progenitors from caspase-3-dependent apoptosis.
Otic vesicles were isolated from HH18 chicken embryos and cultured for 20 h in serum-free culture medium without additives (0S; a and a′), in the presence of IGF-I (10 nM; b and b′) or the pan-caspase inhibitor BOC (50 µM; c and c′). Cell death was visualized by TUNEL staining (green), and immunostaining for activated-caspase-3 (red) was performed. Light microscopy images are also shown for comparison (a–c). BOC treatment caused a reduction in the AVG size (c, arrowhead) and the otic epithelium appeared thickened (c, arrow). The boxed area in a′ is shown at a higher magnification in d, which shows the TUNEL-positive nuclei surrounded by activated caspase-3. Representative images of six otic vesicles per condition and from at least three independent experiments are shown, and they were obtained from compiled confocal microscopy projections of otic vesicles. A, anterior; D, dorsal. Scale bar, 150 µm.