Degeneration and cleavage of htt in YAC transgenic mice with 72 CAG repeats. A, Semithin striatal sections from wild-type (WT) and YAC72 (line 44) transgenic mice stained with toluidine blue. Healthy neurons appear clear (white arrowhead), and degenerating neurons appear darkly stained (black arrows). B, Western blots of cortex from 2-, 4-, 6-, and 11-month-old YAC72 (line 44) transgenic mice or wild-type littermate controls. Blots were probed with BKP1 (top portion) and GAPDH (bottom portion) for a loading control (left panel), Htt552 (center panel), and 1C2 (right panel). Intact htt is indicated by anopen arrowhead and is detected by BKP1 (normal and expanded) and by 1C2 (expanded). The specific 100 and 70 kDa caspase cleavage products of expanded (cleaved mut) and normal (cleaved WT) alleles are indicated by theclosed and open arrows, respectively. Expanded cleaved htt is detected by all three antibodies, where as only BKP1 and Htt552 detect cleaved htt with a normal CAG repeat.