Specific neurotransmitters, their receptors and ion channels localized to synaptic termini, play important roles in behavior and synaptic plasticity. Dopamine receptors, characterized by seven trans-membrane domains, are known to act through G-protein coupled pathways. In C. elegans, dopamine has been implicated in a variety of behavioral processes, including both non-associative and associative learning. The worm dop-2 gene represents a dopamine auto-receptor expressed in dopaminergic neurons (Suo et al., 2003). D2-like auto-receptors have been proposed to regulate the release of dopamine from the pre-synaptic neurons as well as reuptake by DAT (Williams and Galli, 2006; Voglis and Tavernarakis, 2008). We are interested in interacting partners of dop-2 and are using its gene product as bait in a ubiquitin-based yeast two hybrid screen.

In the process of reverse transcriptase PCR amplification of worm total RNA we serendipitously amplified an additional splice variant of dop-2, besides the 2 variants K09G1.4a and K09G1.4b (Suo et al., 2003). This third full-length mRNA (K09G1.4c, Figure-1) has 27 additional nucleotides at the 3’ end of exon-8 neighboring the exon:intron junction. The additional sequence codes for 9 amino-acids in the large intracellular loop between trans-membrane domains 5 and 6. The resulting motif (GDLPLPMLL) does not display similarity to any known motif through Pfam match. Interestingly, the regional splicing of all three variants including intron-7 and intron-8 is the conserved GC-AT junction sequence, and not GC-AG commonly found in splice variants in worms and humans (Farrer et al., 2002).