H3.3 Barcoding of Nucleus Accumbens Transcriptional Activity Identifies Novel Molecular Cascades Associated with Cocaine Self-administration in Mice

Abstract

Although numerous epigenetic modifications have been associated with addiction, little work has explored the turnover of histone variants. Uniquely, the H3.3 variant incorporates stably and preferentially into chromatin independently of DNA replication at active sites of transcription and transcription factor binding. Thus, genomic regions associated with H3.3-containing nucleosomes are particularly likely to be involved in plasticity, such as following repeated cocaine exposure. A recently developed mouse line expressing a neuron-specific hemagglutinin (HA)-tagged H3.3 protein was used to track transcriptionally active sites cumulatively across 19 d of cocaine self-administration. RNA-seq and H3.3-HA ChIP-seq analyses were performed on NAcc tissue collected following cocaine or food self-administration in male mice. RNA sequencing revealed five genes upregulated in cocaine relative to food self-administering mice: Fosb, Npas4, Vgf, Nptx2, and Pmepa1, which reflect known and novel cocaine plasticity-associated genes. Subsequent ChIP-seq analysis confirmed increased H3.3 aggregation at four of these five loci, thus validating H3.3 insertion as a marker of enhanced cocaine-induced transcription. Further motif recognition analysis of the ChIP-seq data showed that cocaine-associated differential H3.3 accumulation correlated with the presence of several transcription factor binding motifs, including RBPJ1, EGR1, and SOX4, suggesting that these are potentially important regulators of molecular cascades associated with cocaine-induced neuronal plasticity. Additional ontological analysis revealed differential H3.3 accumulation mainly near genes involved in neuronal differentiation and dendrite formation. These results establish the H3.3-HA transgenic mouse line as a compelling molecular barcoding tool to identify the cumulative effects of long-term environmental perturbations, such as exposure to drugs of abuse.

Postmitotic accumulation of histone variant H3.3 in new cortical neurons establishes neuronal chromatin, transcriptome, and identity

“…Together, our data support crucial H3.3 functions in the developmental acquisition, but not long-term maintenance, of neuronal identity, and we identify the first postmitotic days as a critical window for de novo H3.3. Previous studies have reported a role for H3.3 in plasticityrelated transcription in adult brain (21,95). Although we find in dKO-R no changes in the developmental acquisition of much of the neuronal transcriptome, we do find a number of differentially regulated genes in dKO-R L5 PT that are associated with synaptic activity.…”

Additive, synergic and antagonistic interactions between maternal immune activation and peripubertal stress in cocaine addiction-like behaviour, morphofunctional brain parameters and striatal transcriptome

“…These categories include 'regulation of postsynaptic neurotransmitter receptor activity', 'regulation of ion transport' (including 'activation of G protein gated potassium channels') and 'cognition'. Some members of the pentraxin gene family that we found modulated here (Nptxr | Nptx1 | Nptx2) (Figure 5, F; Table S5) are involved in anxiety and responses to stress (42), which support their modulation in stressed animals, and more importantly, they are involved in synaptic processes related to cocaine self-administration, cocaine-induced rearrangements of AMPA receptor trafficking and also in the modulation of cocaine-associated memories (43)(44)(45). According to these data, this family of proteins could be partially responsible for the increase in self-administration observed in LPS-exposed stressed rats compared to their controls.…”

More than Addiction—The Nucleus Accumbens Contribution to Development of Mental Disorders and Neurodegenerative Diseases

“…Among the important mechanisms determining the development of addiction are epigenetic processes, which involve the modification of the DNA structure and binding with histone proteins [ 24 ]. The influence of environmental stimuli on the activation or suppression of transcription and, consequently, on changes in gene expression could occur in this way.…”

“…The influence of environmental stimuli on the activation or suppression of transcription and, consequently, on changes in gene expression could occur in this way. The specific regions in the genome rich in histone H3.3 are believed to indicate DNA sequences of genes binding with transcription factors involved in the cocaine-induced plasticity (e.g., Npas4, Nptx2, Pmepa1, Vgf, and Fosb) [ 24 ]. Alterations to the expression of the relevant genes may induce changes in BDNF concentration [ 25 , 26 ], morphogenesis of dendrites and the dendritic spines, along with an increase in their density [ 27 ], and clustering of AMPARs in synapses [ 21 ].…”

“…Alterations to the expression of the relevant genes may induce changes in BDNF concentration [ 25 , 26 ], morphogenesis of dendrites and the dendritic spines, along with an increase in their density [ 27 ], and clustering of AMPARs in synapses [ 21 ]. The consequence of these processes could be behavioral reactions, such as cocaine-conditioned place preference, drug self-administration, cocaine-induced locomotor activity, and spatial memory disturbances [ 24 ]. Altogether, the data indicate the involvement of various mechanisms of cocaine action upon the NAc during the development of addiction.…”