| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Bakalkin, Georgy, et al.
(author)
-
Prodynorphin mutations cause the neurodegenerative disorder spinocerebellar ataxia type 23.
- 2010
-
In: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 87:5, s. 593-603
-
Journal article (peer-reviewed)abstract
- Spinocerebellar ataxias (SCAs) are dominantly inherited neurodegenerative disorders characterized by progressive cerebellar ataxia and dysarthria. We have identified missense mutations in prodynorphin (PDYN) that cause SCA23 in four Dutch families displaying progressive gait and limb ataxia. PDYN is the precursor protein for the opioid neuropeptides, α-neoendorphin, and dynorphins A and B (Dyn A and B). Dynorphins regulate pain processing and modulate the rewarding effects of addictive substances. Three mutations were located in Dyn A, a peptide with both opioid activities and nonopioid neurodegenerative actions. Two of these mutations resulted in excessive generation of Dyn A in a cellular model system. In addition, two of the mutant Dyn A peptides induced toxicity above that of wild-type Dyn A in cultured striatal neurons. The fourth mutation was located in the nonopioid PDYN domain and was associated with altered expression of components of the opioid and glutamate system, as evident from analysis of SCA23 autopsy tissue. Thus, alterations in Dyn A activities and/or impairment of secretory pathways by mutant PDYN may lead to glutamate neurotoxicity, which underlies Purkinje cell degeneration and ataxia. PDYN mutations are identified in a small subset of ataxia families, indicating that SCA23 is an infrequent SCA type (~0.5%) in the Netherlands and suggesting further genetic SCA heterogeneity.
|
|
| 5. |
- Bazov, Igor, 1973-, et al.
(author)
-
Downregulation of the neuronal opioid gene expression concomitantly with neuronal decline in dorsolateral prefrontal cortex of human alcoholics
- 2018
-
In: Translational Psychiatry. - : NATURE PUBLISHING GROUP. - 2158-3188. ; 8
-
Journal article (peer-reviewed)abstract
- Molecular changes in cortical areas of addicted brain may underlie cognitive impairment and loss of control over intake of addictive substances and alcohol. Prodynorphin (PDYN) gives rise to dynorphin (DYNs) opioid peptides which target kappa-opioid receptor (KOR). DYNs mediate alcohol-induced impairment of learning and memory, while KOR antagonists block excessive, compulsive-like drug and alcohol self-administration in animal models. In human brain, the DYN/KOR system may undergo adaptive changes, which along with neuronal loss, may contribute to alcohol-associated cognitive deficit. We addressed this hypothesis by comparing the expression levels and co-expression (transcriptionally coordinated) patterns of PDYN and KOR (OPRK1) genes in dorsolateral prefrontal cortex (dlPFC) between human alcoholics and controls. Postmortem brain specimens of 53 alcoholics and 55 controls were analyzed. PDYN was found to be downregulated in dlPFC of alcoholics, while OPRK1 transcription was not altered. PDYN downregulation was confined to subgroup of subjects carrying C, a high-risk allele of PDYN promoter SNP rs1997794 associated with alcoholism. Changes in PDYN expression did not depend on the decline in neuronal proportion in alcoholics, and thereby may be attributed to transcriptional adaptations in alcoholic brain. Absolute expression levels of PDYN were lower compared to those of OPRK1, suggesting that PDYN expression is a limiting factor in the DYN/KOR signaling, and that the PDYN downregulation diminishes efficacy of DYN/KOR signaling in dlPFC of human alcoholics. The overall outcome of the DYN/KOR downregulation may be disinhibition of neurotransmission, which when overactivated could contribute to formation of alcohol-related behavior.
|
|
| 6. |
- Bazov, Igor, 1973-, et al.
(author)
-
Dynorphin and κ-Opioid Receptor Dysregulation in the Dopaminergic Reward System of Human Alcoholics.
- 2018
-
In: Molecular Neurobiology. - : Springer. - 0893-7648 .- 1559-1182. ; 55:8, s. 7049-7061
-
Journal article (peer-reviewed)abstract
- Molecular changes induced by excessive alcohol consumption may underlie formation of dysphoric state during acute and protracted alcohol withdrawal which leads to craving and relapse. A main molecular addiction hypothesis is that the upregulation of the dynorphin (DYN)/κ-opioid receptor (KOR) system in the nucleus accumbens (NAc) of alcohol-dependent individuals causes the imbalance in activity of D1- and D2 dopamine receptor (DR) expressing neural circuits that results in dysphoria. We here analyzed post-mortem NAc samples of human alcoholics to assess changes in prodynorphin (PDYN) and KOR (OPRK1) gene expression and co-expression (transcriptionally coordinated) patterns. To address alterations in D1- and D2-receptor circuits, we studied the regulatory interactions between these pathways and the DYN/KOR system. No significant differences in PDYN and OPRK1 gene expression levels between alcoholics and controls were evident. However, PDYN and OPRK1 showed transcriptionally coordinated pattern that was significantly different between alcoholics and controls. A downregulation of DRD1 but not DRD2 expression was seen in alcoholics. Expression of DRD1 and DRD2 strongly correlated with that of PDYN and OPRK1 suggesting high levels of transcriptional coordination between these gene clusters. The differences in expression and co-expression patterns were not due to the decline in neuronal proportion in alcoholic brain and thereby represent transcriptional phenomena. Dysregulation of DYN/KOR system and dopamine signaling through both alterations in co-expression patterns of opioid genes and decreased DRD1 gene expression may contribute to imbalance in the activity of D1- and D2-containing pathways which may lead to the negative affective state in human alcoholics.
|
|
| 7. |
- Bazov, Igor
(author)
-
Epigenetic Dysregulations in the Brain of Human Alcoholics : Analysis of Opioid Genes
- 2016
-
Doctoral thesis (other academic/artistic)abstract
- Neuropeptides are special in their expression profiles restricted to neuronal subpopulations and low tissue mRNA levels. Genetic, epigenetic and transcriptional mechanisms that define spatiotemporal expression of the neuropeptide genes have utmost importance for the formation and functions of neural circuits in normal and pathological human brain. This thesis focuses on regulation of transcription of the opioid/nociceptin genes, the largest neuropeptide family, and on identification of adaptive changes in these mechanisms associated with alcoholism as model human pathology. Two epigenetic mechanisms, the common for most cells in the dorsolateral prefrontal cortex (dlPFC) and the neuron-subpopulation specific that may orchestrate prodynorphin (PDYN) transcription in the human dlPFC have been uncovered. The first, repressive mechanism may operate through control of DNA methylation/demethylation in a short, nucleosome size promoter CpG island (CGI). The second mechanism may involve USF2, the sequence–specific methylation–sensitive transcription factor which interaction with its target element in the CpG island results in USF2 and PDYN co-expression in the same neurons. The short PDYN promoter CGI may function as a chromatin element that integrates cellular and environmental signals through changes in methylation and transcription factor binding. Alterations in USF2–dependent PDYN transcription are affected by the promoter SNP (rs1997794: T>C) under transition to pathological state, i.e. in the alcoholic brain. This and two other PDYN SNPs that are most significantly associated with alcoholism represent CpG-SNPs, which are differentially methylated in the human dlPFC. The T, low risk allele of the promoter SNP forms a noncanonical AP-1–binding element. JUND and FOSB proteins, which may form homo- or heterodimers have been identified as dominant constituents of AP-1 complex. The C, non-risk variant of the PDYN 3′ UTR SNP (rs2235749 SNP: C>T) demonstrated significantly higher methylation in alcoholics compared to controls. PDYN mRNA and dynorphin levels significantly and positively correlated with methylation of the PDYN 3′ UTR CpG-SNP suggesting its involvement in PDYN regulation. A DNA–binding factor with differential binding affinity for the T allele and methylated and unmethylated C alleles of the PDYN 3′ UTR SNP (the T allele specific binding factor, Ta-BF) has been discovered, which may function as a regulator of PDYN transcription. These findings emphasize the complexity of PDYN regulation that determines its expression in specific neuronal subpopulations and suggest previously unknown integration of epigenetic, transcriptional and genetic mechanisms that orchestrate alcohol–induced molecular adaptations in the human brain. Given the important role of PDYN in addictive behavior, the findings provide a new insight into fundamental molecular mechanisms of human brain disorder. In addition to PDYN in the dlPFC, the PNOC gene in the hippocampus and OPRL1 gene in central amygdala that were downregulated in alcoholics may contribute to impairment of cognitive control over alcohol seeking and taking behaviour.
|
|
| 8. |
- Bazov, Igor, 1973-, et al.
(author)
-
Neuronal Expression of Opioid Gene is Controlled by Dual Epigenetic and Transcriptional Mechanism in Human Brain
- 2018
-
In: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 28:9, s. 3129-3142
-
Journal article (peer-reviewed)abstract
- Molecular mechanisms that define patterns of neuropeptide expression are essential for the formation and rewiring of neural circuits. The prodynorphin gene (PDYN) gives rise to dynorphin opioid peptides mediating depression and substance dependence. We here demonstrated that PDYN is expressed in neurons in human dorsolateral prefrontal cortex (dlPFC), and identified neuronal differentially methylated region in PDYN locus framed by CCCTC-binding factor binding sites. A short, nucleosome size human-specific promoter CpG island (CGI), a core of this region may serve as a regulatory module, which is hypomethylated in neurons, enriched in 5-hydroxymethylcytosine, and targeted by USF2, a methylation-sensitive E-box transcription factor (TF). USF2 activates PDYN transcription in model systems, and binds to nonmethylated CGI in dlPFC. USF2 and PDYN expression is correlated, and USF2 and PDYN proteins are co-localized in dlPFC. Segregation of activatory TF and repressive CGI methylation may ensure contrasting PDYN expression in neurons and glia in human brain.
|
|
| 9. |
|
|
| 10. |
- Bazov, Igor, 1973-, et al.
(author)
-
Prodynorphin Epialleles
- 2016
-
In: Epigenetics and Neuroendocrinology. - Cham : Springer. - 9783319299006 - 9783319299013 ; , s. 43-76
-
Book chapter (peer-reviewed)abstract
- Dynorphins, the endogenous ligands for kappa-opioid receptors play an essential role in neuroendocrine regulation, stress response, reward processing, and mood control. These neuropeptides induce strong dysphoric and aversive effects. Polymorphisms in the prodynorphin (PDYN), the dynorphin-encoding gene, are associated with substance addiction and negative craving, while dynorphin mutations cause neurodegeneration in the human brain. Similarly to other neuropeptide genes, PDYN is expressed in selective neural circuits at extremely low tissue levels. A sophisticated epigenetic/transcriptional regulation by cell lineage-specific transcription factors (TFs), insulators, and silencers such as CCCTC-binding factor (CTCF) and RE1-silencing transcription factor (REST) along with mechanisms that control neuronal activity-dependent transcription may define spatial, temporal, and adaptive PDYN expression patterns. Impairment of the epigenetic control of PDYN expression may contribute to human pathological conditions including substance dependence, depression, and chronic pain. Epigenetic and environmental factors may mechanistically converge on the PDYN CpG-SNPs associated with a risk for alcohol dependence, and the resulting methylation signals may be translated into disease predisposition via alterations in PDYN transcription. Understanding the mechanisms that regulate neuropeptide epigenome and transcriptome is essential for understanding of neuropeptide-mediated functional connectivity within neural circuits which activities define cognition and behavior.
|
|
