Figure 2. SCA1 mice develop immature protrusion morphology and loss of dendritic protrusions, associated with persisting synaptic instability after symptom onset.

(a,f) In vivo two-photon imaging of dendrites in 6- and 8-week-old Sca1^2Q/2Q mice (n = 14 dendrites from five mice and n = 12 dendrites from four mice, respectively) and Sca1^154Q/2Q mice (n = 14 dendrites from five mice and n = 10 dendrites from five mice, respectively). Repeated imaging of the same dendrites over 1 h in each group showed increased formation (filled arrowhead) and elimination (open arrowheads) of dendritic protrusions in Sca1^154Q/2Q mice at 6 and 8 weeks of age. (b,g) Dendritic protrusion density in 6- and 8-week-old Sca1^2Q/2Q and Sca1^154Q/2Q mice. Sca1^154Q/2Q mice exhibited decreased spine density at both 6 (b) and 8 (g) weeks of age. (c,h) Spines and filopodia as a percentage of total protrusions in Sca1^2Q/2Q and Sca1^154Q/2Q mice at 6 (c) and 8 (h) weeks of age. The percentage of spines was lower, and filopodia higher, in 8-week-old Sca1^154Q/2Q mice than in Sca1^2Q/2Q mice, whereas no differences were observed in 6-week-old Sca1^154Q/2Q mice. (d,i) Percentage of total spines formed and eliminated. Sca1^154Q/2Q mice showed higher formation and elimination rates of spines than Sca1^2Q/2Q mice at 6 (d) and 8 (i) weeks of age. (e,j) Percentage of total filopodia formed and eliminated. Formation and elimination rates were greater in 6- (f) and 8-week-old Sca1^154Q/2Q mice than in Sca1^2Q/2Q mice (k). Data are presented as the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001, Student t-test. Scale bar, 5 μm.