The molecular components of vesicle fusion machinery are encoded by several multi-gene families (Sudhof, 2013), but it is not clear how different gene family members shape transmitter and neuropeptide release properties (Moghadam and Jackson, 2013). We revealed a comprehensive molecular profiles of vesicle release machinery in PCPs (Figure 6F–I). Several core components of the fusion complex and active zone are broadly expressed, including Syntaxins (AUROC=0.5), SNAP complex (AUROC=0.614), RIMs and RIM binding proteins (AUROC=0.57) (Table S4). Yet even among these core components, VAMP (synaptobrevins) and SNAP members are significantly enriched in specific PCPs (Figure 6F–H). The vesicular Ca2+ sensor synaptotagmins (Syt) show more distinct patterns: 14 of the 17 Syts are differentially expressed among PCPs (Figure 6G–I; AUROC=0.78); individual neurons express 6–9 Syts. In particular, VIP/CCK cells specifically express Syt10 that mediates the release of Igf1 (Cao et al., 2011), which is also highly enriched in the same cells (Figure 6F, D). These results suggest that each PCP might deploy a specific set of Syts with different sensitivity to spatiotemporal Ca2+ signals that trigger particular types of fusion reactions, thereby shaping the specificity and properties in parallel exocytosis pathways.
