Figure 4

Type II BMP receptor expression in dI neurons. (A) Western analysis of whole cell lysates of dissociated dI neurons probed with α-BMPRII (130 kDa, lane 1), α-ActRIIA/B (70 kDa, lane 2) and α-ActRIIB (58 kDa, lane 3) antibodies. (B) Immunofluorescence labeling of dissociated dI neurons with antibodies against type II BMP receptors (α-BMPRII, α-ActRIIA/B and α-ActRIIB). The left column shows relative numbers of labeled neurons against background low level fluorescence (scale = 50 μm). The center column (scale = 20 μm) and right column (scale = 10 μm) highlight neuronal detail. (C) Direct comparison of ActRIIA and ActRIIB expression in sister cultures. Phase contrast (left), BMP receptor immunofluorescence labeling (center) and DAPI nuclear staining (right) of dissociated dI neurons. Arrowheads indicate ActRIIB⁺ growth cones. Analysis of immunofluorescence label for each antibody from three to four 20 × fields showed that 85.6 ± 3.7% of 1,056 total neurons were ActRIIA⁺ (n = 4), 33.1 ± 3.7% of 732 total neurons were ActRIIB⁺ (n = 4) and 78.6 ± 3.3% of 465 total neurons were BMPRII⁺ (n = 3). Scale = 50 μm.