Genomic Insights into Opioid Addiction: Identification of genomic variants from Gene Expression data

Next-generation sequencing (NGS) has transformed high-throughput DNA and RNA analysis, facilitating the rapid identification of clinically relevant genetic variants. Opioid Use Disorder (OUD), a chronic condition characterized by relapse and remission cycles, poses significant challenges for genomic investigations. While whole-exome sequencing (WES) and whole-genome sequencing (WGS) serve as robust approaches for variant detection, their high cost restricts widespread use. RNA sequencing (RNA-Seq) presents a viable alternative; however, the complexity of the transcriptome complicates reliable variant identification. Despite these challenges, RNA-Seq has emerged as a valuable tool for detecting single nucleotide polymorphisms (SNPs) in conditions with limited WES data, such as OUD. In this study, RNA-Seq data from postmortem ventral midbrain specimens of chronic opioid users (PRJNA492904) were analyzed to identify variants associated with OUD. Given its established involvement in opioid addiction and impulsivity, we hypothesized that the NRXN3 gene would harbor a significant number of variants. Variant analysis was conducted across eight genes: BDNF, DRD2, DRD3, NRXN3, OPRD1, OPRM1, and NGFB —with a primary focus on NRXN3 . Our results revealed that NRXN3 exhibited the highest variant burden among the analyzed genes, highlighting its potential role in OUD pathogenesis and reinforcing its association with opioid addiction.