Western blot of 10 ug of HEK 293 cells expressing: Lane 1 - HEK cells without NR1 expression (Mock); Lane 2 - NR1 subunit containing only the C2 Insert; Lane 3 - NR1 subunit containing the C1 and C2' Insert; Lane 4 - NR1 subunit containing the N1 and C2' Insert showing specific immunolabeling of the ~120k NR1 subunit of the NMDA receptor containing the C1 splice variant insert.