Figure 8: Gαs antagonizes YAP and TAZ to control SC proliferation.

(a,b) EGR2 and OCT6 immunostaining (a) and quantification (b) in the sciatic nerves of control and Gnas^cKO sciatic nerves at P7. Nuclei were counterstained with DAPI. n=3 animals/genotype. (c,d) SOX2 immunostaining (c) and quantification (d) in the sciatic nerves of control and Gnas^cKO sciatic nerves at P7. n=3 animals/genotype. (e,f) Ki67 and SOX10 immunostaining (e) and quantification of Ki67⁺SOX10⁺ cells relative to SOX10⁺ cells (f) in the control and Gnas^cKO sciatic nerves at P7. n=3 animals per genotype. The experiment was repeated on 3 different sections per animal. (g) Immunofluorescence images show BrdU and Ki67 expression in rat SCs with treated with indicated siRNAs, cultured in neuregulin-supplemented SC growth media. (h,i) Quantification of (h) BrdU⁺ and (i) Ki67⁺ cells among SCs transfected with indicated siRNA (n=3 (h) and 4 (i) independent experiments). BrdU pulse was for 6 h. (j) Immunofluorescence images show BrdU and Ki67 expression in rat SCs transfected with vectors indicated. Cells were cultured in mitogen-deprived DMEM/10% FBS. BrdU pulse was for 6 h. (k,l) Quantification of the proportion of (k) BrdU⁺ and (l) Ki67⁺ SCs transfected with indicated vectors (n=3 (k) and 4 (l) independent experiments). (m) Schematic diagram of TAZ/YAP and Gαs-signalling feedback-loop in regulating the transition from SC proliferation to differentiation. Under SC proliferation conditions, YAP/TAZ repress Gnas expression and promote SC proliferation. At the onset of SC differentiation, Gnas expression is upregulated and Gαs functions as a negative feedback regulator to attenuate TAZ/YAP activity. During myelin formation when Gαs levels decline, YAP and TAZ cooperate with SOX10 to activate the transcriptional programme necessary for SC myelination. Data are presented as means±s.e.m. Each experiment was repeated 3 times. *P<0.05, **P<0.01; ***P<0.001. (b,d,f) Two-tailed unpaired Student’s t-test; (h,i,k,l); one-way ANOVA with Tukey’s multiple comparisons test. Scale bars in a,c,e=50 μm; g,j=25 μm.