We next describe the role of PARP1 activation and the effects of its inhibition in the pathogenesis of neurological disorders, such as in a rare cerebellar ataxia caused by biallelic loss of function mutations of XRCC1, Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) [94,109,110]. The gene discussed is PARP1; the disease is Alzheimer disease.