Fig. 6. Neuronal subtype-inducing properties of NGN1 and MASH1 at different concentrations of BMP2. At each concentration of BMP2, cultures infected with NGN1 (A), MASH1 (B) or control GFP (A,B) retroviruses were fixed and double-labeled with antibodies to BRN3A or PHOX2B, and GFP. The percentage of infected (GFP⁺) cells co-expressing BRN3A or PHOX2B is plotted. The data are pooled from 11 experiments, although not all BMP2 concentrations were tested in every experiment. For additional quantification see Table 2. Note that in B, although the percentage of MASH1-infected cells expressing PHOX2B in 10 ng/ml BMP2 (25%; red triangles) is similar to the percentage of MASH1- or GFP-infected cells expressing BRN3A (red and blue dots), this similarity is coincidental; PHOX2B and BRN3A are never co-expressed (not shown). (C) The percentage of BRN3A⁺ and neuronal (TuJ1⁺) cells among NGN1-infected cells is directly compared. Note that the enhancement of the sensory marker is always greater than the enhancement of neuronal differentiation. The fold-induction of BRN3A expression declines with increasing BMP concentration because the level of baseline BRN3A expression increases (see A); see also Table 2. *P<.05; other values are not significantly different from each other.