CALCA and Huntington disease: The principal interaction network of the α-synuclein gene (SNCA) predicted that besides SNCA playing a key role in neuroinflammation and Huntington’s disease, displayed direct interactions with amyloid beta precursor protein (APP), clusterin (CLU), and neural precursor cell expressed developmentally down-regulated protein 4 (also called NEDD4 E3 ubiquitin-protein ligase; NEDD4) genes, whereas it showed indirect relationships with calcitonin related polypeptide alpha (CALCA) and superoxide dismutase 1 (SOD1) genes (Figure 3A).