Dopamine from the ventral tegmental area and glutamate from several brain nuclei converge in the nucleus accumbens (NAc) to drive motivated behaviors. Repeated activation of D2 receptors with quinpirole (QNP) induces locomotor sensitization and compulsive behaviors, but the mechanisms are unknown. In this study, in vivo microdialysis and fast scan cyclic voltammetry in adult anesthetized rats were used to investigate the effect of repeated QNP on dopamine and glutamate neurotransmission within the NAc. Following eight injections of QNP, a significant decrease in phasic and tonic dopamine release was observed in rats that displayed locomotor sensitization. Either a systemic injection or the infusion of QNP into the NAc decreased dopamine release, and the extent of this effect was similar in QNP-sensitized and control rats, indicating that inhibitory D2 autoreceptor function is maintained despite repeated activation of D2 receptors and decreased dopamine extracellular levels. Basal extracellular levels of glutamate in the NAc were also significantly lower in QNP-treated rats than in controls. Moreover, the increase in NAc glutamate release induced by direct stimulation of medial prefrontal cortex was significantly lower in QNP-sensitized rats. Together, these results indicate that repeated activation of D2 receptors disconnects NAc from medial prefrontal cortex and ventral tegmental area.

RCOR1 is a known transcription repressor that recruits and positions LSD1 and HDAC1/2 on chromatin to erase histone methylation and acetylation. However, there is currently an incomplete understanding of RCOR1’s range of localization and function. Here, we probe RCOR1’s distribution on a genome-wide scale and unexpectedly find that RCOR1 is predominantly associated with transcriptionally active genes. Biochemical analysis reveals that RCOR1 associates with RNA Polymerase II (POL-II) during transcription and deacetylates its carboxy-terminal domain (CTD) at lysine 7. We provide evidence that this non-canonical RCOR1 activity is linked to dampening of POL-II productive elongation at actively transcribing genes. Thus, RCOR1 represses transcription in two ways—first, via a canonical mechanism by erasing transcriptionally permissive histone modifications through associating with HDACs and, second, via a non-canonical mechanism that deacetylates RNA POL-II’s CTD to inhibit productive elongation. We conclude that RCOR1 is a transcription rheostat.

Prenatal ethanol exposure is associated with neurodevelopmental defects and long-lasting cognitive deficits, which are grouped as fetal alcohol spectrum disorders (FASD). The molecular mechanisms underlying FASD are incompletely characterized. Alternative splicing, including the insertion of microexons (exons of less than 30 nucleotides in length), is highly prevalent in the nervous system. However, whether ethanol exposure can have acute or chronic deleterious effects in this process is poorly understood. In this work, we used the bioinformatic tools VAST-TOOLS, rMATS, MAJIQ, and MicroExonator to predict alternative splicing events affected by ethanol from available RNA sequencing data. Experimental protocols of ethanol exposure included human cortical tissue development, human embryoid body differentiation, and mouse development. We found common genes with predicted differential alternative splicing using distinct bioinformatic tools in different experimental designs. Notably, Gene Ontology and KEGG analysis revealed that the alternative splicing of genes related to RNA processing and protein synthesis was commonly affected in the different ethanol exposure schemes. In addition, the inclusion of microexons was also affected by ethanol. This bioinformatic analysis provides a reliable list of candidate genes whose splicing is affected by ethanol during nervous system development. Furthermore, our results suggest that ethanol particularly modifies the alternative splicing of genes related to post-transcriptional regulation, which probably affects neuronal proteome complexity and brain function.

Null mice for the dopamine D2 receptor (D2R) have been instrumental in understanding the function of this protein. For our research, we obtained the functional D2R knockout mouse strain described initially in 1997. Surprisingly, our biochemical characterization showed that this mouse strain is not a true knockout. We determined by sequence analysis of the rapid 3′ amplification of cDNA ends that functional D2R knockout mice express transcripts that lack only the eighth exon. Furthermore, immunofluorescence assays showed a D2R-like protein in the brain of functional D2R knockout mice. We verified by immunofluorescence that the recombinant truncated D2R is expressed in HEK293T cells, showing intracellular localization, colocalizing in the Golgi apparatus and the endoplasmic reticulum, but with less presence in the Golgi apparatus compared to the native D2R. As previously reported, functional D2R knockout mice are hypoactive and insensitive to the D2R agonist quinpirole. Concordantly, microdialysis studies confirmed that functional D2R knockout mice have lower extracellular dopamine levels in the striatum than the native mice. In conclusion, functional D2R knockout mice express transcripts that lead to a truncated D2R protein lacking from the sixth transmembrane domain to the C-terminus. We share these findings to avoid future confusion and the community considers this mouse strain in D2R traffic and protein–protein interaction studies.

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27Null mice for the dopamine D2 receptor (D2R) have been instrumental in understanding 28 the function of this protein in the central nervous system. Several lines of D2R knockout 29 mice have been generated, which share some characteristics but differ in others. The D2R 30 functional knockout mouse, first described in 1997, is functionally null for D2R-mediated 31 signaling but the Drd2 gene was interrupted at the most extreme distal end leaving open 32 the question about whether transcript and protein are produced. We decided to determine 33 if there are D2R transcripts, the characteristics of these transcripts and whether they are 34 translated in the brain of D2R functional knockout mice. Sequence analysis of 3' Rapid 35Amplification of cDNA Ends showed that D2R functional knockout mice express 36 transcripts that lack only the exon eight. Immunofluorescence showed D2R-like protein 37 in the brain of the knockout mice. As previously reported, D2R functional knockout mice 38 are hypoactive and insensitive to the D2R agonist quinpirole (QNP). However, the 39 heterozygous showed locomotor activity and response to QNP similar to the wild-type 40 mice. Intriguingly, microdialysis experiments showed that heterozygous mice, such as 41 knockouts, have half the normal levels of synaptic dopamine in the striatum. However, 42 heterozygous mice responded similarly to wild-type mice to an acute injection of QNP, 43 showing a 50% decrease in synaptic dopamine. In conclusion, D2R functional knockout 44 mice express transcripts that lead to a truncated D2R protein that lacks from the sixth 45 transmembrane domain to the C-terminal end but retains the third intracellular loop. We 46 discuss the implications of this truncated D2R coexisting with the native D2R that may 47 explain the unexpected outcomes observed in the heterozygous. Finally, we suggest that 48 the D2R functional knockout mouse can be a useful model for studying protein-protein 49 interaction and trafficking of D2R. 50 3 51 Introduction 52 Dopamine is a neurotransmitter that participates in the control of voluntary 53 movements and motivated behaviors, among other relevant functions. Two types of 54 receptors mediate the action of dopamine, type 1 receptors coupled to excitatory G protein 55 and which include D1 and D5, and type 2 receptors coupled to inhibitory G protein, which 56 include D2, D3 and D4 receptors. D2 receptors (D2R) exist as two splice variants, the 57 long (D2L) and the short (D2S) variants that differ in 29 amino acids in the third 58 intracellular loop [1, 2]. Cumulated evidence indicate that D2L variant mediates mainly 59 dopamine postsynaptic actions whereas D2S variant mediates presynaptic control of 60 dopamine release and dopamine neurons firing [3]. Although, more recently it was 61 described that under basal conditions both isoforms are able to play postsynaptic 62 functions [4]. 63 D2R are especially abundant in the striato-pallidal efferent GABA medium spiny 64 neurons (MSN) that are involved in the control of voluntary movements...