Considering our finding of differential transcript usage, we were intrigued to follow up on the possible requirement of spliceosomal proteins such as cell division cycle 5-like protein (Cdc5). A GFP-tagged version of Cdc5 was expectantly observed within nuclei throughout the adult central brain (Figure 5A, i and ii), including within MB neurons (Figure 5A, iii and iv). To test the necessity of Cdc5 in ethanol-cue-induced memory, Cdc5-RNAi was expressed during the adult stage using a pan-MB-specific Gal4 driver (R19B03-Gal4) (Figure S9A). Flies with adult Cdc5 knockdown had significant impairment in ethanol-cue-induced memory as compared to genetics controls (Figure 5B). To determine whether Cdc5 could affect individual Stat92E transcript expression, we performed whole-head quantitative RT-PCR with primers specific to each alternative first exon in the Stat-92E transcripts, where Exon1 includes Stat92E-RH and Exon1a includes Stat92E-RI (Henriksen et al. 2002) (Figure 5C, Figure S8A). Decreasing expression of Cdc5 in all adult neurons significantly altered the ratio of Exon1 to 1a (Stat92E-RH to -RI) transcripts (Figure 5D, Figure S8B).
