FIGURE 10.

Htt N-terminal fragments of specific size have different toxic properties. A, Western blot of total cell extracts from HT22 cells transfected with the indicated Htt constructs. Htt proteins were detected with an antibody to exon 1 of Htt. B, cell viability, measured by luciferase assay (see “Experimental Procedures”) of HT22 cells, expressing the indicated Htt construct co-transfected with the luciferase construct (n = 3, ^*, p = 0.016 N117-82Q versus N171-82Q, p < 0.05 for all normal repeat versus expanded repeat constructs). One representative experiment of three for each set of constructs is shown. C, cytotoxicity, measured by caspase 3 activation (see “Experimental Procedures”) of HT22 cells, expressing the indicated Htt construct. Results are presented as a percentage of Htt positive cells co-expressing active caspase 3 (n = 2, over 100 cells were counted for each condition, ^**, p < 0.05 N117-82Q versus N171-82Q). One representative experiment of two is shown.