Machine Learning Analysis of the Orbitofrontal Cortex Transcriptome of Human Opioid Users Identifies Shisa7 as a Translational Target Relevant for Heroin Seeking Leveraging a Male Rat Model.

Abstract

BACKGROUND: Identifying neurobiological targets predictive of the molecular neuropathophysiological signature of human opioid use disorder (OUD) could expedite new treatments. OUD is characterized by dysregulated cognition and goal-directed behavior mediated by the orbitofrontal cortex (OFC), and next-generation sequencing could provide insights regarding novel targets. METHODS: Here, we used machine learning to evaluate human postmortem OFC RNA sequencing datasets from heroin users and control participants to identify transcripts that were predictive of heroin use. To determine a causal link to OUD-related behaviors, we examined the effects of overexpressing the top target gene in a translational rat model of heroin seeking and behavioral updating. Additionally, we determined the effects of overexpression on the rat OFC transcriptome compared with that of human heroin users. Co-immunoprecipitation/mass spectrometry (co-IP/MS) from the rat OFC elucidated the protein complex of the novel target. RESULTS: Our machine learning approach identified SHISA7 as predictive of human heroin users. Shisa7 is understudied but appears to be an auxiliary protein of GABA(gamma-aminobutyric acid A) or AMPA receptors. In rats, Shisa7 expression positively correlated with heroin-seeking behavior. Overexpressing Shisa7 in the OFC augmented heroin seeking and impaired behavioral updating for sucrose-based operant contingency. RNA sequencing of rat OFC revealed gene coexpression networks regulated by Shisa7 overexpression similar to human heroin users. Finally, co-IP/MS showed that heroin influenced Shisa7 binding to glutamatergic and GABAergic receptor subunits. Both gene expression signatures and Shisa7 protein complex emphasized perturbations of neurodegenerative and neuroimmune processes. CONCLUSIONS: Our findings suggest that OFC Shisa7 is a critical driver of neurobehavioral pathology related to drug-seeking behavior and behavioral updating, thus identifying a potential therapeutic target for OUD.