Fig. 6. BMP signaling decreases neuron numbers in vivo and in vitro. (A) Neuron numbers in the trigeminal ganglion and DRG of K14-noggin animals and the DRG of the K14-BMP4 animals normalized to their respective wild-type controls for each ganglion. Neuron numbers were significantly increased in the trigeminal and dorsal root ganglia of the K14-noggin animals, but significantly reduced in the DRGs of K14-BMP4 animals. The mean and s.e.m. of seven wild-type and seven transgenic ganglia are shown. ^*P<0.02; ^**P<0.01; ^***P<0.015. (B) Preferential increase of the smaller size neuronal population in K14-noggin trigeminal ganglia. The means and s.e.m. of three wild-type and four transgenic ganglia are shown. ^*P<0.05; ^**P<0.005. (C) Effects of BMP4 and NGF on cultured trigeminal neurons. E10 trigeminal ganglia were dissociated, and 600 cells were plated per well in the presence of BDNF (5 ng/ml). Six hours after plating, some cultures were treated with BMP4 (30 ng/ml), NGF (10 ng/ml), or both, or with additional BDNF (10 ng/ml). Cell numbers were counted 72 hours later and are expressed as mean±s.e.m. per dish. Note that BMP4 treatment reduced cell survival. Treatment with NGF but not additional BDNF prevented the BMP4-mediated cell death (^*P<0.04 using ANOVA).