Novel Differentially-Expressed Genes in the Study of Opioid Addiction

Drug abuse is a rising epidemic in many parts of the world, from the United States to Southeast Asia. Opioids, in particular, have seen increased usage due to a combination of increased opioid prescriptions and the development of highly efficient synthetic opioids. The influence of opioid receptor and dopamine receptor genes in opioid addiction has been well-studied over the years, but there may be other genetic factors involved in opioid dependency disorders. The nucleus accumbens is a region important in the study of opioid addiction due to its relation to the dopaminergic system as well as its central role in the biochemistry of reward and aversion. In this study, we investigated the genomics of the nucleus accumbens. Microarray and RNA-sequencing gene expression sets related to opioid addiction were searched in the NCBI-GEO database and analysed to discover differentially expressed genes (DEGs) between opioid addicted samples and normal samples. The top DEGs were selected and the STRING database was used to depict and analyse the relationship between the proteins encoded for by said genes. Most of the pathways involved with upregulated DEGs suggested apoptosis and cellular death as the main pathways connecting these genes,while most of the pathways involved with downregulated DEGs were related to exocytosis and protein transport. While these connections have been noted in other studies, we have also determined DEGs that may be novel to the study of opioid addiction, such as the Y-chromosome specific gene USP9Y, the long non-coding RNA LINC00336, as well as the HAUS subunit pseudogene, which is part of the HAUS complex. As these genes do not currently fit into the major pathways of drug addiction, we think they may be interesting targets of research in future studies.