For example, cortical neurons carrying mutations in the PSEN1 gene exhibit amyloid β pathology characteristic of Alzheimer’s disease262; dopaminergic neurons carrying mutations in the SNCA gene exhibit α-synuclein aggregation characteristic of Parkinson’s disease320; and motor neurons carrying mutations in the TDP-43 gene exhibit TDP-43 aggregation characteristic of ALS.321 However, most cases of neurodegenerative diseases are sporadic and do not have a clear etiology. The gene discussed is SNCA; the disease is amyotrophic lateral sclerosis.