Figure 8.

Sorbitol, a chemical chaperone, promoted the structuring of diffusible assemblies of mHtt to form IBs and supported survival of the E14 rat striatal neuron–derived ST14A cell line. ST14A cells were transfected with the HttQ74–EGFP plasmid DNA and then plated in 96-well plate (day 0) according to methods described in the text. Sorbitol was added to designated wells of cells to a final concentration of 150 mm at 24 h after plating (day 1). A–D, for cell imaging, cells were fixed 72 h after plating (day 3) and processed to stain for HSP70 and nuclei according to methods described in the text. A and B are images of the control and C and D are of sorbitol-treated (150 mm, 48 h) cells. These images are representative of results from two separate experiments each with eight independent samples. E, to test for survival of the control and sorbitol-treated cells under stress, the culture medium was changed to DMEM without serum and cells were moved from a 33 °C to a 39 °C incubator on day 2 after plating. Cell viability was determined 2 days after the shift to this restrictive condition using the CellTiter-Glo reagent from Promega (G7572). Result represents the average of viability readouts (3X each sample) of 16 independent samples per condition from two separate experiments. F, the time line of the experiment is as shown. Probability of difference <0.001 is extremely significant (***). Error bars represent S.D.