Fig 1: BAI1 restricts dendrite growth in the developing hippocampus and hippocampal cultures.(a) Representative in vivo images showing optical sections through the centers of neuronal somata from mice transfected with EGFP and shRNA against Adgrb1 and stained for BAI1. Note that the transfected neuron expressing EGFP and shRNA has substantially lower BAI1 staining that the neighboring untransfected neuron, indicating successful BAI1 knockdown. (b) 100 µm thick slices of dorsolateral CA1 from mice transfected with EGFP (Control) or EGFP and shRNA against BAI1 (BAI1 Kd). Bar is 50 µm. c and d Reconstructions of representative control (c) and BAI1 Kd (d) dendritic arbors from slices like those in b. (e) Summary data for dendrite length. (f) Summary data for dendrite number. (g) Summary data for branch points. (h) Summary data for dendrite penetration. Total number of neurons: 21 (N = 3) for control and 41 (N = 4) for BAI1 Kd. (i) Representative images of neurons expressing EGFP alone (control) or with shRNA against Adgrb1 (BAI1 Kd) or with shRNA against BAI1 and RNAi-resistant BAI1 (Rescue). Images are masked to remove axons and dendrites from other neurons. Bar is 20 µm. (j) Summary data for total length of cultured neurons. (k) Summary data for total dendrite number in cultured neurons. Total number of neurons in j and k: 118 for control neurons, 106 for BAI1 Kd neurons, and 65 for rescue neurons (N = 7). Data are represented as mean ± s.e.m. (***p<0.001) Detailed statistics are found in Figure 1—source data 1.10.7554/eLife.47566.010Figure 1—source data 1.Statistical summary for Figure 1: ANOVA and key Tukey post-hoc tests and N and n values for Figure 1e–h,j–k.10.7554/eLife.47566.007Figure 1—source data 2.Individual values for in vivo and cultured neurons demonstrating the effects of BAI1 loss on arbor growth (Figure 1e–h,j–k).10.7554/eLife.47566.008Figure 1—source data 3.Quantification of Western bands showing expression levels of BAI1, BAI2, and BAI3 (Figure 1—figure supplement 1d).10.7554/eLife.47566.009Figure 1—source data 4.Extended individual values for in vivo and cultured neurons showing the effects of BAI1 loss on arbor growth (Figure 1—figure supplement 1a,b,e,g,h,i,j).