The effect of expressing human huntingtin fragments containing polyglutamine 
(polyQ) tracts of varying lengths was assessed in Caenorhabditis elegans ASH 
sensory neurons in young and old animals. Expression of a huntingtin fragment 
containing a polyQ tract of 150 residues (Htn-Q150) led to progressive ASH 
neurodegeneration but did not cause cell death. Progressive cell death and 
enhanced neurodegeneration were observed in ASH neurons that coexpressed 
Htn-Q150 and a subthreshold dose of a toxic OSM-10::green fluorescent protein 
(OSM-10::GFP) fusion protein. Htn-Q150 huntingtin protein fragments formed 
protein aggregates in ASH neurons, and the number of ASH neurons containing 
aggregates increased as animals aged. ASH neuronal cell death required ced-3 
caspase function, indicating that the observed cell death is apoptotic. Of 
interest, ced-3 played a critical role in Htn-Q150-mediated neurodegeneration 
but not in OSM10::GFP-mediated ASH neurodegeneration. ced-3 function was 
important but not essential for the formation of protein aggregates. Finally, 
behavioral assays indicated that ASH neurons, coexpressing Htn-Q150 and 
OSM10::GFP, were functionally impaired at 3 days before the detection of 
neurodegeneration, cell death, and protein aggregates.