Regulation of transposons within medium spiny neurons enables molecular and behavioral responses to cocaine

Abstract

A more complete understanding of the molecular mechanisms by which substance use is encoded in the brain could illuminate novel strategies to treat substance use disorders, including cocaine use disorder (CUD). We have previously discovered that Zfp189, which encodes a Kruppel-associated box zinc finger protein (KZFP) transcription factor (TF), differentially accumulates in nucleus accumbens (NAc) Drd1+ and Drd2+ medium spiny neurons (MSNs) over the course of cocaine exposure and is causal in producing MSN functional and behavioral changes to cocaine1. Here, we aimed to illuminate the brain cell-type specific molecular mechanisms through which this KZFP TF produces CUD-related brain changes, with emphasis on investigating transposable elements (TEs), since KZFPs like ZFP189 are known regulators of TEs2-6. First, we annotated TEs in existing single nuclei RNA-sequencing (snRNAseq) datasets of rodents that were exposed to either acute or repeated cocaine. We discovered that expression of NAc TEs was dramatically altered by cocaine experience, the most sensitive NAc cell-type was MSNs, and TEs in Drd1+ MSNs were considerably more dynamic over the course of cocaine exposure than TEs in Drd2+ MSNs. To determine the causality of this TE dysregulation within NAc MSNs in cocaine-induced brain changes, we virally delivered conditional synthetic ZFP189 TFs of our own design to Drd1+ or Drd2+ MSNs. These synthetic ZFP189 TFs are capable of directly activating (ZFP189VPR) or repressing (ZFP189WT) brain TEs2. We discover that behavioral and cell morphological adaptations to cocaine are produced by activating TEs with ZFP189VPR in Drd1+ MSNs or stabilizing TEs with ZFP189WT in Drd2+ MSNs, revealing a persistent opponent process balanced across MSN subtypes and weighted by TE stability and consequent gene expression within MSN subtype. We next performed snRNAseq of the whole NAc virally manipulated with ZFP189 TFs. We observed that, relative to ZFP189WT, NAc manipulated with ZFP189VPR impeded cocaine-induced gene expression in NAc cell-types, including both Drd1+ and Drd2+ MSNs. Within either MSN subtype, the consequence of normal ZFP189 function was to enhance immune-related gene expression, and ZFP189VPR impeded these gene expression profiles. We finally performed cocaine intravenous self-administration to determine the consequence of NAc ZFP189-mediated transcriptional control on cocaine use behaviors. We observed that ZFP189VPR impeded any increases in active lever responses following a period forced cocaine abstinence. This research demonstrates that KZFP-mediated transcriptional repression of TEs within NAc MSNs is a causal molecular step in enabling gene expression and subsequent cellular and behavioral responses to cocaine use, and the use of ZFP189VPR in this work demonstrates cell-type specific mechanistic strategies to block CUD-related brain adaptations, which may inform future CUD treatments.