Role of Rif in spinogenesis. (A) Mouse hippocampal neurons were transfected with GFP alone, or with GFP and myc-tagged inactive Rif or constitutively active Rif at DIV 11. Cells were fixed at DIV 12, and expression of Rif myc constructs was detected by anti-myc antibody (not depicted). Bars, 5 µm. (B) Quantitative analysis of neurons expressing inactive Rif (inact Rif) did not reveal significant changes in dendritic protrusion density as compared with wild-type cells (wt). Dendritic protrusion length was slightly reduced. Numerical data and p-values are presented in Table IV. (C) Dendritic protrusion morphology analysis of neurons expressing inactive Rif revealed a significant decrease in the number of thin spines and an increase in the number of stubby spines. Numerical data and p-values are presented in Tables I and II. (D) Quantitative dendritic protrusion analysis of neurons expressing active Rif (act Rif) revealed a significant reduction in dendritic protrusion density, whereas the mean length of dendritic protrusions was comparable to wild-type cells (wt). Numerical data are presented in Table IV. (E) Dendritic protrusion morphology analysis of neurons expressing active Rif did not reveal statistically significant changes between GFP and active Rif-transfected cells. Numerical data are shown in Tables I and II. Graphs represent mean ± SEM.