HTT and Alzheimer disease: Casp2 has been implicated in mouse models of four neurodegenerative diseases —the rTg4510 model of frontotemporal dementia (FTD) [23], which expresses mutant human tau, the J20 mouse model of AD [15], which expresses mutant human APP, the YAC128 mouse model of HD [2], which expresses mutant human huntingtin, and the MPTP mouse model of Parkinson’s disease (PD) [19].