Figure 4. Genetic reduction of p110β restores dysregulated mGlu5-mediated protein synthesis, normalizes dendritic spine density, but does not shorten prolonged UP states in Fmr1^KO mice.

(A) Increased basal protein synthesis rates in Fmr1^KO cortical synaptic fractions, measured by incorporation of radiolabeled amino acids, were significantly reduced by genetic reduction of p110β (2-way ANOVA, p(Fmr1)=0.004, F(1,33)=9.5; p(Pik3cb)=0.005, F(1,33)=8.8; p(interaction)=0.257, F(1,33)=1.3).

(B) Genetic reduction of p110β restores an increase in protein synthesis rates upon mGlu1/5 stimulation in Fmr1^KO cortical synaptic fractions (50 mM DHPG for 20 min; 2-way ANOVA, p(Fmr1)=0.001, F(1,33)=13.5; p(Pik3cb)=0.057, F(1,33)=3.9; p(interaction)=0.047, F(1,33)=4.3; *p=0.001, #p=0.003). N represents individual mice from at least 5 different litters.

(C,D) Genetic reduction of p110β normalizes the increased dendritic spine density in CA1 apical dendrites to WT levels (2-way ANOVA, p(Fmr1)=0.014, F(1, 67)=6.4; p(Pik3cb)=0.659, F(1,67)=0.2; p(interaction)=0.001, F(1,67)=11.2; *p=0.0006, #p=0.039). Example images are shown on the left, quantification of number of dendritic spines per 10μm is shown on the right. N indicates number of secondary dendrites analyzed (60–100μm length each, starting from the primary shaft), 3–4 mice/genotype, 4–8 neurons/mouse, 1–2 dendrites/neuron. See Figure S4 for additional analyses. Scale bar is 3μm.

(E) Genetic reduction of p110β reduces the increased susceptibility to audiogenic seizures in Fmr1^KO mice (Fisher’s exact tests, *p<0.0001; #p=0.012).

(F,G) Genetic reduction of p110β does not affect duration of UP states in acute thalamocortical slices from Fmr1^KO mice. Example traces for each genotype are shown in (F), and quantification in (G) (2-way ANOVA, p(Fmr1)<0.0001, F(1, 108)=39.8; p(Pik3cb)=0.203, F(1,108)=1.6; p(interaction)=0.61, F(1,108)=0.26). N indicates number of slices from at least three individual mice per genotype.

Error bars represent SEM.