Generation of iPSC Lines with Tagged α-Synuclein for Visualization of Endogenous Protein in Human Cellular Models of Neurodegenerative Disorders.

α-Synuclein is a synaptic protein that accumulates primarily in synucleinopathies and secondarily in certain lysosomal storage disorders. However, its physiological roles in health and disease are not fully understood. In part, this has been hampered by the inability to visualize α-synuclein and its cellular localization, due to the lack of specific antibodies and faithful reporters. Here, we used CRISPR/Cas9-based genome editing to generate human-induced pluripotent stem cell (iPSC) lines in which the α-synuclein (SNCA) gene has been tagged with the short HA peptide either at the N-terminus or C-terminus or with the fluorescent protein mCherry at the C-terminus of the protein. These diverse strategies revealed the C-terminus HA-tag as the best option. C-Terminus HA-tagged α-synuclein had unchanged protein expression and did not generate degradation by-products. Importantly, we show that following differentiation to neurons, the C-terminus HA-tagged iPSC line had unaffected electrophysiological properties and could be used to visualize accumulation of α-synuclein upon inhibition of lysosomal function and under physiological protein levels. It is our expectation that this line and tagging approach will be very useful in further studies examining α-synuclein aggregation and its role in cellular dysfunction and neurodegeneration.