DIFFERENTIAL EXPRESSION OF TRANSCRIPTS FROM SYB, A DROSOPHILA-MELANOGASTER GENE ENCODING VAMP (SYNAPTOBREVIN) THAT IS ABUNDANT IN NONNEURONAL CELLS

VAMP (synaptobrevin) is a highly conserved membrane protein originally described as a component of brain synaptic vesicles. The Drosophila m elanogaster VAMP-encoding gene (syb) comprises five exons. Splicing ex ons 1,2,3,4,5 (syb-b) results in a protein with a C-terminal hydrophob ic domain and a negligible intraluminal domain. Splicing exons 1,2,3,5 (syb-a) predicts a protein with a 20-amino-acid luminal domain at the C terminus. The ratio of syb-a to syb-b transcripts is highly regulat ed during development. The syb transcripts show no enrichment in the n ervous system and are present in very early embryos, well before neuro genesis. The greatest concentration of syb transcripts was found in ce lls of the gut and malpighian tubules. Thus, syb may have a general ro le in membrane trafficking and, perhaps, a role in the secretion of di gestive enzymes.