The first three coding exons (aa2-107; 3R:5514628..5516383 , FB2018_02) of Nmdar1 is deleted and replaced with a "T2A-Gal4-STOP" cassette containing the GAL4 coding sequence and a 3P3-RFP marker flanked by loxP sites. This results in GAL4 being expressed under the control of Nmdar1 regulatory sequences, with the Nmdar1 coding region knocked-out.