Progressive rotarod deficits developed simultaneously to a lowering of exploratory activity in R6/2 mice.

<p>Latency to fall from an accelerating rotarod against exploratory activity measured in an open field for all R6/2 mice; data points were separated into the three ages investigated, at 5, 9 and 13 weeks of age. Positive correlations were detected between these two tasks over time due to the simultaneous development of deficits in both male (r = 0.507, **p<.01) and female (r = 0.5, **p<.01) R6/2.</p

<i>In vivo</i> MRI sample images.

<p>(A) Sample T2-weighted images for structural volumetry assessments. Images are from scans taken at 4, 8, 12 and 14 weeks of age at anatomically matching slices. (B) Hot/cold scaled maps of T2 relaxation times for the study of T2 relaxivity, these are represented on anatomically identical images to those in (A). Bg = bregma.</p

MRI assessment of brain volumetry and T2 relaxivity in WT and R6/2.

<p>(A) Regional brain volumes assessed through MRI (volumetry) became progressively smaller in both male and female R6/2 mice versus WT, with the exception of the female R6/2 corpus callosum, which did not differ as compared to WT at any age. (B) T2 relaxation times (T2 relaxivity) progressively shortened for both WT and R6/2 with age, but this was significantly exacerbated in the R6/2 in all regions of interest investigated. Data presented as means ± SEM; males: *p<.05, **p<.01, ***p<.001, females: ^#p<.05, ^##p<.01,^###p<.001.</p

Quantification of mHTT accumulation.

<p>(A) Representative coronal sections from 14 weeks old WT and R6/2 mouse brains stained with the S830 antibody for the detection of mHTT. Levels were quantified within seven brain regions using an intensity threshold-based image analysis tool optimized for the detection of nuclear inclusions, or total levels of mHTT (neuropil aggregates and diffuse nuclear accumulation, highlighted in blue); scale bar 50 µm. Percentage of sampled field of views (FOVs) positive for S830 stain of nuclear inclusions (B), and percentage of FOV positive for total mHTT (C); there were no significant differences between male and female R6/2 for either assessments. Regional differences in mHTT reflect cellular density. STR = striatum, CTX = cortex, HIPP = hippocampus, DG = dentate gyrus, CA1 = hippocampal CA1 subfield, CA2 = hippocampal CA2 subfield, CA3 = hippocampal CA3 subfield. Data presented as means ± SEM.</p

mHTT accumulation in <i>Hdh</i>Q150 mice.

<p>(A) Sample S830-stained brain sections of a WT and <i>Hdh</i>Q150 mouse. Threshold-intensity-based analysis was used to descriminate nuclear mHTT inclusions versus total aggregated mHTT levels in the striatum (STR), cortex (CTX), dentate gyrus (DG), hippocampal CA3 subfield (CA3), hippocampal CA2 subfield (CA2) and hippocampal CA1 subfield (CA1). There were no significant differences in mHTT levels between male and female <i>Hdh</i>Q150 mice in the regions investigated. All data presented as means ± SEM.</p

Longitudinal <i>in vivo</i> MRI.

<p>(A) Summed T2-weighted structural group-images from WT and R6/1 mice at 9 and 17 weeks of age. (B) R6/1 mice progressive lost regional brain volumes compared to WT controls, with the exception of the corpus callosum (C. Callosum). Analyzed using a three-way ANOVA (Genotype X Gender X Age). Striatum, cortex, hippocampus, corpus callosum and whole brain: WT male n=11, R6/1 male n=9, WT female n=10, R6/1 female n=9-10. All data presented as means ± SEM; *p<0.05, **p<0.01, ***p<0.001.</p

Performance at non-motor-related tasks.

<p>Male R6/1 mice did not exhibit any impairment in cue learning in the swimming T-maze (A), whereas female R6/1 mice were deficient at 15 weeks of age (B). Both male (C) and female (D) R6/1s developed an age related deficit in cue reversal learning in a swimming T-maze. There was no obvious difference in cued extinction behavior between WTs and R6/1s (E & F), or a difference in contextual recall (G & H). At the odor discrimination task (I) and novel social interaction test (J) there was no difference between the four groups. Swimming T-maze analyzed using three-way ANOVA (Age X Genotype X Gender); fear conditioning cue extinction analyzed using a repeated measures ANOVA (Genotype X Gender X Tone); fear conditioning context recall, odor discrimination and novel social interaction analyzed using a two-way ANOVA (Genotype X Gender). Swimming T-maze: WT male n=10-11, R6/1 male n=8-9, WT female n=10, R6/1 female n=9-10; Fear conditioning: WT male n=11, R6/1 male n=9, WT female n=7-8, R6/1 female n=7-8; Odor discrimination: WT male n=11, R6/1 male n=8, WT female n=9, R6/1 female n=8; Novel social interaction: WT male n=10, R6/1 male n=9, WT female n=10, R6/1 female n=10. All data presented as means ± SEM; *p<0.05, **p<0.01.</p

Concomitant deficits in behavioral tasks result in a robust correlation of those two measures.

<p>(A) At 18 weeks of age R6/1 mice have both lower forelimb, and fore- and hind limb grip strength capacity to a similar degree, separating the data from those of WT resulting in a significant, positive correlation (r=0.79, p<0.005). (B) Between 15-19 weeks of age R6/1 mice have lower fore- and hind limb grip strength, as well as impaired cue reversal learning in a swimming T-maze to a similar degree, forming a strong overall negative correlation (r=-0.669, p<0.005). </p

Brain volume changes in female WT and R6/1 assessed through TBM.

<p>Maps of local volumetric changes in female R6/1 mice compared to female WT 9 weeks <i>in </i><i>vivo</i> (A), 17 weeks <i>in </i><i>vivo</i> (B), and at 19 weeks <i>ex </i><i>vivo</i> (C). Images presented as either both global volume change (6 dof), or region-specific changes corrected for global change (9 dof). Color scales are for volume difference (Volume diff., blue-to-yellow), and the raw <i>t</i> statistical value at each voxel (dark-to-light green). Only volume changes and effects-sizes which survive multiple comparisons corrections across all voxels in the brain (False Discovery Rate with q<0.05) are shown.</p