Figure 5

BMP6/BMP7 chimeras exhibit dramatically different growth cone collapse activity from that of BMP6 WT. (A) Western blot analysis of whole cell lysates of COS-1 cells expressing control vector (pMT23) and HA-tagged native (WT) and chimeric BMP constructs. The bands represent the 60 kDa BMP proprotein. The fully processed form is secreted into the COS-1 cell medium which is used as CM in growth cone collapse assays. (B) Growth cone collapse activity of WT and chimeric BMPs. Percentage decrease of growth cone area relative to control cultures (mean ± SEM): rBMP7 = 36.7 ± 0.3%; BMP7 WT = 40.7 ± 4.0%; BMP6 WT = 11.5 ± 2.3%; BMP6 N65Y = 13.3 ± 4.9%; BMP6 Y98T = 20.4 ± 3.1%; BMP6 Q48R = 49.8 ± 4.5%; BMP6 Q48A = 46.8 ± 5.0%; BMP7 R48Q = 26.7 ± 5.7%. Student’s t tests: BMP6 Q48R- and BMP6 Q48A-evoked reduction of growth cone area is significantly different from BMP6 WT treated cultures (***P = 0.0004 and ***P = 0.0007, respectively). BMP6 Q48R- and BMP6 Q48A-stimulated growth cone collapse is not different from BMP7 WT treated cultures (P = 0.2600 and P = 0.4425, respectively). Results are for 100 to 250 growth cones/condition/experiment; n = 2.