DNA Methylation within the Amygdala Early in Life Increases Susceptibility for Depression and Anxiety Disorders

The role of epigenetics in anxiety disorders

Anxiety disorders (ADs) are extremely common psychiatric conditions that frequently co-occur with other physical and mental disorders. The pathophysiology of ADs is multifaceted and involves intricate connections among biological elements, environmental stimuli, and psychological mechanisms. Recent discoveries have highlighted the significance of epigenetics in bridging the gap between multiple risk factors that contribute to ADs and expanding our understanding of the pathomechanisms underlying ADs. Epigenetics is the study of how changes in the environment and behavior can have an impact on gene function. Indeed, researchers have found that epigenetic mechanisms can affect how genes are activated or inactivated, as well as whether they are expressed. Such mechanisms may also affect how ADs form and are protected. That is, the bulk of pharmacological trials evaluating epigenetic treatments for the treatment of ADs have used histone deacetylase inhibitors (HDACi), yielding promising outcomes in both preclinical and clinical studies. This review will provide an outline of how epigenetic pathways can be used to treat ADs or lessen their risk. It will also present the findings from preclinical and clinical trials that are currently available on the use of epigenetic drugs to treat ADs.

DNA methylation patterns and gene expression from amygdala tissue of mature Brahman cows exposed to prenatal stress

Prenatal stress can alter postnatal performance and temperament of cattle. These phenotypic effects may result from changes in gene expression caused by stress-induced epigenetic alterations. Specifically, shifts in gene expression caused by DNA methylation within the brain’s amygdala can result in altered behavior because it regulates fear, stress response and aggression in mammals Thus, the objective of this experiment was to identify DNA methylation and gene expression differences in the amygdala tissue of 5-year-old prenatally stressed (PNS) Brahman cows compared to control cows. Pregnant Brahman cows (n = 48) were transported for 2-h periods at 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 days of gestation. A non-transported group (n = 48) were controls (Control). Amygdala tissue was harvested from 6 PNS and 8 Control cows at 5 years of age. Overall methylation of gene body regions, promoter regions, and cytosine-phosphate-guanine (CpG) islands were compared between the two groups. In total, 202 genes, 134 promoter regions, and 133 CpG islands exhibited differential methylation (FDR ≤ 0.15). Following comparison of gene expression in the amygdala between the PNS and Control cows, 2 differentially expressed genes were identified (FDR ≤ 0.15). The minimal differences observed could be the result of natural changes of DNA methylation and gene expression as an animal ages, or because this degree of transportation stress was not severe enough to cause lasting effects on the offspring. A younger age may be a more appropriate time to assess methylation and gene expression differences produced by prenatal stress.

N6-Methyladenine in Eukaryotic DNA: Tissue Distribution, Early Embryo Development, and Neuronal Toxicity

DNA methylation is one of the most important epigenetic modifications and is closely related with several biological processes such as regulation of gene transcription and the development of non-malignant diseases. The prevailing dogma states that DNA methylation in eukaryotes occurs essentially through 5-methylcytosine (5mC) but recently adenine methylation was also found to be present in eukaryotes. In mouse embryonic stem cells, 6-methyladenine (6mA) was associated with the repression and silencing of genes, particularly in the X-chromosome, known to play an important role in cell fate determination. Here, we have demonstrated that 6mA is a ubiquitous eukaryotic epigenetic modification that is put in place during epigenetically sensitive periods such as embryogenesis and fetal development. In somatic cells there are clear tissue specificity in 6mA levels, with the highest 6mA levels being observed in the brain. In zebrafish, during the first 120 h of embryo development, from a single pluripotent cell to an almost fully formed individual, 6mA levels steadily increase. An identical pattern was observed over embryonic days 7–21 in the mouse. Furthermore, exposure to a neurotoxic environmental pollutant during the same early life period may led to a decrease in the levels of this modification in female rats. The identification of the periods during which 6mA epigenetic marks are put in place increases our understanding of this mammalian epigenetic modification, and raises the possibility that it may be associated with developmental processes.

Upregulation of KDM6B contributes to lipopolysaccharide-induced anxiety-like behavior via modulation of VGLL4 in mice

Histone H3K27me3 demethylase KDM6B (also known as Jumonji domain-containing protein D3, JMJD3) plays vital roles in the etiology of inflammatory responses; however, little is known about the role of KDM6B in neuroinflammation-induced anxiety-like behavior. The present study aimed to investigate the potential role of KDM6B in lipopolysaccharide (LPS)-induced anxiety-like behavior and to evaluate whether it is associated with the modulation of vestigial-like family member 4 (VGLL4). The elevated plus maze, light-dark box, and open-field test were performed to test the anxiety-like behavior induced by LPS in C57BL/6 J male mice. Levels of relative protein expression in the hippocampus were quantified by western blotting. KDM6B inhibitor GSK-J4 and microglia inhibitor minocycline as well as adeno-associated virus of Vgll4 shRNA were used to explore the underlying mechanisms. We found that KDM6B, VGLL4, interleukin-1β (IL-1β), and ionized calcium-binding adaptor molecule-1 (Iba-1, microglia marker) protein levels were increased in LPS-dose dependent manner in the hippocampus but not in prefrontal cortex. GSK-J4 treatment attenuated LPS-induced VGLL4, the signal transducer and activator of transcription 3 (STAT3), IL-1β and Iba-1 upregulation and anxiety-like behavior. Knockdown VGLL4 with Vgll4 shRNA prevented the increase of anxiety-like behavior and levels of STAT3, IL-1β, and Iba-1 expression in the hippocampus of LPS-treated mice. Moreover, minocycline, an inhibitor of microglia treatment blunted LPS-induced anxiety-like behavior. Collectively, these results demonstrate that the induction of neuroinflammation by LPS promotes KDM6B activation in the hippocampus, and LPS-induced anxiety-like behavior is associated with upregulation of VGLL4 by KDM6B in the hippocampus.