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Background: The onset and persistence of addiction phenotypes are, in part, mediated by transcriptional mechanisms in the brain that affect gene expression and, subsequently, neural circuitry. ΔFosB is a transcription factor that accumulates in the nucleus accumbens (NAc)-a brain region responsible for coordinating reward and motivation-after exposure to virtually every known rewarding substance, including cocaine and opioids. ΔFosB has also been shown to directly control gene transcription and behavior downstream of both cocaine and opioid exposure, but with potentially different roles in D1 and D2 medium spiny neurons (MSNs) in NAc., Methods: To clarify MSN subtype-specific roles for ΔFosB and investigate how these coordinate the actions of distinct classes of addictive drugs in NAc, we developed a CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9-based epigenome editing tool to induce endogenous ΔFosB expression in vivo in the absence of drug exposure. After inducing ΔFosB in D1- or D2-MSNs or both, we performed RNA sequencing on bulk male and female NAc tissue (n = 6-8/group)., Results: We found that ΔFosB induction elicits distinct transcriptional profiles in NAc by MSN subtype and by sex, establishing for the first time that ΔFosB mediates different transcriptional effects in males versus females. We also demonstrated that changes in D1-MSNs, but not those in D2-MSNs or both, significantly recapitulate changes in gene expression induced by cocaine self-administration., Conclusions: Together, these findings demonstrate the efficacy of a novel molecular tool for studying cell type-specific transcriptional mechanisms and shed new light on the activity of ΔFosB, a critical transcriptional regulator of drug addiction., (Copyright © 2021 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: Lasting changes in gene expression in brain reward regions, including nucleus accumbens (NAc), contribute to persistent functional changes in the addicted brain. We and others have demonstrated that altered expression of several candidate transcription factors in NAc regulates drug responses. A recent large-scale genome-wide study from our group predicted transcription factor E2F3 (E2F3) as a prominent upstream regulator of cocaine-induced changes in gene expression and alternative splicing., Methods: We studied expression of two E2F3 isoforms-E2F3a and E2F3b-in mouse NAc after repeated cocaine administration and assayed the effects of overexpression or depletion of E2f3 isoforms in NAc on cocaine behavioral responses. We then performed RNA sequencing to investigate the effect of E2f3a overexpression in this region on gene expression and alternative splicing and performed quantitative chromatin immunoprecipitation at downstream targets in NAc following E2f3a overexpression or repeated cocaine exposure. Sample sizes varied between experiments and are noted in the text., Results: We showed that E2f3a, but not E2f3b, overexpression or knockdown in mouse NAc regulates cocaine-induced locomotor and place conditioning behavior. Furthermore, we demonstrated that E2f3a overexpression substantially recapitulates genome-wide transcriptional profiles and alternative splicing induced by cocaine. We further validated direct binding of E2F3a at key target genes following cocaine exposure., Conclusions: This study establishes E2F3a as a novel transcriptional regulator of cocaine action in NAc. The findings reveal a crucial role for E2F3a in the regulation of cocaine-elicited behavioral states. Moreover, the importance of this role is bolstered by the extensive recapitulation of cocaine's transcriptional effects in NAc by overexpression of E2f3a., (Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

The ability of neurons to respond to external stimuli involves adaptations of gene expression. Induction of the transcription factor ΔFOSB in the nucleus accumbens, a key brain reward region, is important for the development of drug addiction. However, a comprehensive map of ΔFOSB's gene targets has not yet been generated. We used CUT&RUN (cleavage under targets and release using nuclease) to map the genome-wide changes in ΔFOSB binding in the 2 main types of nucleus accumbens neurons—D1 or D2 medium spiny neurons—after chronic cocaine exposure. To annotate genomic regions of ΔFOSB binding sites, we also examined the distributions of several histone modifications. Resulting datasets were leveraged for multiple bioinformatic analyses. The majority of ΔFOSB peaks occur outside promoter regions, including intergenic regions, and are surrounded by epigenetic marks indicative of active enhancers. BRG1, the core subunit of the SWI/SNF chromatin remodeling complex, overlaps with ΔFOSB peaks, a finding consistent with earlier studies of ΔFOSB's interacting proteins. Chronic cocaine use induces broad changes in ΔFOSB binding in both D1 and D2 nucleus accumbens medium spiny neurons of male and female mice. In addition, in silico analyses predict that ΔFOSB cooperatively regulates gene expression with homeobox and T-box transcription factors. These novel findings uncover key elements of ΔFOSB's molecular mechanisms in transcriptional regulation at baseline and in response to chronic cocaine exposure. Further characterization of ΔFOSB's collaborative transcriptional and chromatin partners specifically in D1 and D2 medium spiny neurons will reveal a broader picture of the function of ΔFOSB and the molecular basis of drug addiction. [ABSTRACT FROM AUTHOR]

Abstract Background Global changes in gene expression underlying circuit and behavioral dysregulation associated with cocaine addiction remain incompletely understood. Here, we show how a history of cocaine self-administration (SA) reprograms transcriptome-wide responses throughout the brain's reward circuitry at baseline and in response to context and/or cocaine re-exposure after prolonged withdrawal (WD). Methods We assigned male mice to one of six groups: saline/cocaine SA + 24-hour WD or saline/cocaine SA + 30-day WD + an acute saline/cocaine challenge within the previous drug-paired context. RNA sequencing was conducted on six interconnected brain reward regions. Using pattern analysis of gene expression and factor analysis of behavior, we identified genes that are strongly associated with addiction-related behaviors and uniquely altered by a history of cocaine SA. We then identified potential upstream regulators of these genes. Results We focused on three patterns of gene expression that reflect responses to 1) acute cocaine, 2) context re-exposure, and 3) drug + context re-exposure. These patterns revealed region-specific regulation of gene expression. Further analysis revealed that each of these gene expression patterns correlated with an addiction index—a composite score of several addiction-like behaviors during cocaine SA—in a region-specific manner. Cyclic adenosine monophosphate response element binding protein and nuclear receptor families were identified as key upstream regulators of genes associated with such behaviors. Conclusions This comprehensive picture of transcriptome-wide regulation in the brain's reward circuitry by cocaine SA and prolonged WD provides new insight into the molecular basis of cocaine addiction, which will guide future studies of the key molecular pathways involved. [ABSTRACT FROM AUTHOR]