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- Bazov, Igor, 1973-, et al.
(author)
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Neuronal Expression of Opioid Gene is Controlled by Dual Epigenetic and Transcriptional Mechanism in Human Brain
- 2018
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In: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 28:9, s. 3129-3142
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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.
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| 3. |
- Taqi, Malik Mumtaz, 1983-
(author)
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Conformational polymorphism of single stranded oligonucleotides with the opioid peptide dynorphin-encoding sequences: effect of CpG methylation and human pathogenic mutations
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Other publication (pop. science, debate, etc.)abstract
- Single stranded DNA (ssDNA) is characterized by high conformational flexibility that allows these molecules to adopt a variety of conformations and form non-canonical DNA secondary structures. We here evaluated whether cytosine methylation at CpG sites affects conformational flexibility of short ssDNA molecules using native polyacrylamide gel electrophoresis (PAGE), nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy. The 37-nucleotide fragments of exon 4 of the PDYN gene that contain four CpG sites were used as model molecules. Some of the analyzed single stranded oligonucleotides demonstrated formation of non-canonical DNA structures at 4oC that were not evident at 37oC. Cytosine methylation at specific CpG sites interfered with the formation of these structures and promoted formation of other conformers at 4oC. Results obtained by the three methods generally correlated. Thus, cytosine methylation may affect conformational flexibility of ssDNA molecules and therefore their propensity to form non-canonical DNA secondary structures. This effect may be potentially relevant for molecular events in the chromatin context including regulation of gene transcription, and DNA replication and recombination where double stranded DNA is unwinded to ssDNA.
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| 4. |
- Taqi, Malik Mumtaz, 1983-
(author)
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Mechanisms of Prodynorphin Gene Dysregulation in the Brain of Human Alcoholics
- 2011
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Doctoral thesis (other academic/artistic)abstract
- The endogenous opioid system (EOS) including dynorphin opioid peptides and κ-opioid receptor (KOR) plays a critical role in alcohol dependence. Aims of the thesis were to evaluate whether the EOS undergoes molecular adaptations in brain areas involved in cognitive control of addiction in human alcohol dependent subjects, and to analyze the impact of genetic and epigenetic factors on these adaptive changes. The main findings were that (1) the dynorphin/KOR system including PDYN mRNA and dynorphins in the dorsolateral prefrontal cortex (dl-PFC), dynorphins in the hippocampus, and KOR mRNA in the orbitofrontal cortex (OFC), is upregulated in human alcoholics. No other significant changes in the EOS were found. (2) Three PDYN single nucleotide polymorphisms (SNPs), which show the most significant association with alcohol dependence, form CpG sites that are methylated in human brain at different levels. Methylation of the C, non-risk variant of the 3’-untranslated region (3’-UTR) SNP (rs2235749; C>T) was increased in dl-PFC and positively correlated with dynorphins. The DNA-binding factor that differentially targeted the T, risk allele and methylated and unmethylated C allele of this SNP was identified in human brain. We hypothesize that influences of the genetic, epigenetic and environmental factors may be integrated through alterations in methylation of the PDYN 3’jUTR CpG/SNP and, as a consequence, affect PDYN transcription and vulnerability to develop alcohol dependence. (3) The principal component analysis suggested that PDYN expression in the dl-PFC may be related to alcoholism, while in the hippocampus may depend on the genotype of the PDYN promoter SNP (rs1997794; T>C). The T, low risk allele of this SNP resides within non-canonical AP-1-binding element and may be targeted by JUND and FOSB proteins, the dominant AP-1 constituents in the human brain. The T to C transition abrogated AP-1 binding. The impact of genetic variations on PDYN transcription may be relevant for diverse adaptive responses of this gene to alcohol. (4) It was proposed that PDYN transcription may be regulated by intragenic DNA regulatory elements controlling the DNA-protein interactions through formation of non-canonical DNA secondary structures. The dynorphin-encoding sequence in PDYN was found to have potential to form such DNA structure in vitro, and this formation was affected by CpG methylation in this region. This methylation sensitive non-canonical DNA structure formation may be involved in regulation of initiation of PDYN transcription from alternative start sites located within this region, or in splicing of non-canonical mRNA. In conclusion, the dynorphin/KOR system has been identified as the site of robust adaptive changes associated with alcohol dependence in the areas of human brain involved in cognitive control of addiction. Regulation of PDYN was found to be brain area specific, apparently affected by the genetic and epigenetic factors, and possibly dependent on the internal properties of the gene such as its ability to form non-canonical DNA secondary structures.
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