Aberrant PAR signaling has been observed in AD for over two decades, and subsequent studies have since provided further support for this link.54,55,66,67 Elevated PARP1 and PAR levels were observed in the AD brain compared to control,54 and higher levels of PARP1 PARylation were observed in AD fibroblasts and lymphoblasts, without changes in overall PARP1 levels.55 Genetic analyses have also linked the PARP1 gene to AD susceptibility,67,68 further highlighting the potential role for PAR in AD pathogenesis. This evidence concerns the gene PARP1 and Alzheimer disease.