Genetic Evidence for Differential Activities of Goa Isoforms in Drosophila Melanogaster

Abstract

Mental illness is prevalent in our population and has been studied for decades but is still poorly understood. Understanding the genetic and biological mechanisms underlying these disorders can lead to significant improvements in diagnosis, treatment, and quality of life for patients suffering from mental disorders. Goα47A is a candidate gene in a putative haloperidol-affected pathway that is highly expressed in the nervous system. The gene encodes nine transcripts and two isoforms, which are 98% identical and differ only in the N-terminal region. However, the individual roles for each of the two different proteins have not yet been discerned. Transgenic strains of Drosophila melanogaster were generated using cDNA constructs corresponding to each of the two open reading frames (ORFs) under the control of UAS promoters. Expression of these transgenes was driven by a GAL4 driver with a similar spatial expression pattern to that of Goα47A. These constructs were intended to be used in a genetic rescue in order to test the hypothesis that a mutant allele of Goα47A causes resistance to the antipsychotic haloperidol. In the course of generating strains needed for the rescue, it was found that the expression of either ORF causes a crumpled wing phenotype and lethality, both with variable penetrance. This variability is likely due to expression level, since GAL80 can reduce the frequency of these phenotypes. Additionally, there is an interaction between the ORFs and the TM3 balancer, which could indicate an interaction between Goα and a gene that is affected by the chromosomal rearrangements associated with the TM3 balancer. The majority of VD1 strains display crumpled wings and the expression of ORF1 can cause lethality. In contrast, two copies of the ORF2 transgene are required to cause crumpled wings. The difference in activities between the two ORFs is likely due to the few changes in the N-terminal region of the protein, which is presumably involved in the interaction with the β and γ subunits. This finding suggests that small differences in a G-protein are sufficient to alter protein-protein interactions and subsequent signalling.