In particular, a small portion of α-synuclein (~4%) is constitutively phosphorylated at Ser129 in the brains of healthy individuals [40,41,42], whereas >90% of the insoluble α-synuclein is phosphorylated in the brain of patients with synucleinopathies [41,43,44,45]. Here, SNCA is linked to synucleinopathy.