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Gliomas, the most common type of malignant primary brain tumor, were conventionally classified through WHO Grades I-IV (now 1-4), with low-grade gliomas being entities belonging to Grades 1 or 2. While the focus of the WHO Classification for Central Nervous System (CNS) tumors had historically been on histopathological attributes, the recently released fifth edition of the classification (WHO CNS5) characterizes brain tumors, including gliomas, using an integration of histological and molecular features, including their epigenetic changes such as histone methylation, DNA methylation, and histone acetylation, which are increasingly being used for the classification of low-grade gliomas. This review describes the current understanding of the role of DNA methylation, demethylation, and histone modification in pathogenesis, clinical behavior, and outcomes of brain tumors, in particular of low-grade gliomas. The review also highlights potential diagnostic and/or therapeutic targets in associated cellular biomolecules, structures, and processes. Targeting of MGMT promoter methylation, TET-hTDG-BER pathway, association of G-CIMP with key gene mutations, PARP inhibition, IDH and 2-HG-associated processes, TERT mutation and ARL9-associated pathways, DNA Methyltransferase (DNMT) inhibition, Histone Deacetylase (HDAC) inhibition, BET inhibition, CpG site DNA methylation signatures, along with others, present exciting avenues for translational research. This review also summarizes the current clinical trial landscape associated with the therapeutic utility of epigenetics in low-grade gliomas. Much of the evidence currently remains restricted to preclinical studies, warranting further investigation to demonstrate true clinical utility.

Background: Late onset dementia due to Alzheimer's disease (AD) has a sex‐biased incidence with females comprising nearly two thirds of all cases. Females have a more rapid progression in cognitive decline and higher levels of known AD biomarker pathology compared to men. Genetic sequence variation does not account for the sex‐biased incidence of AD, directing attention to the emerging role of epigenetics in AD. Using whole genome methylation sequencing (WGMS), we previously reported 28,038 differentially methylated position (DMPs) within 2,707 genes between persons with and without AD. Here we report sex‐specific DNA methylation levels in AD. Method: WGMS data quantified DNA methylation levels at 25,406,945 CpG loci in 281 blood samples from 109 AD (47 female, 62 male) and 174 cognitively unimpaired (CU) individuals (90 female, 84 male) in the Wisconsin Alzheimer's Disease Research Center and the Wisconsin Registry for Alzheimer's Prevention cohorts. Beta‐binomial regression models were developed to test for significant sex‐specific DNA methylation levels between CU and AD accounting for batch effects, estimated white blood cell proportions, BMI, and age. P‐values were corrected and local false discovery rates (lFDRs) were calculated. Result: 13,293 DMPs were identified in females and 20,719 DMPs were identified in males (Figure 1) when comparing CU and AD (lFDR < 0.05; mean methylation difference > 2.5%). Approximately 2% (280) of the DMPs overlap between sexes with 87 having opposite mean methylation differences. The majority of DMPs annotate to introns (55.9% females; 54.8% males) with most of the remainder intergenic (37.0% females; 37.9% males). Annotation of DMPs to genes identified 1,498 genes that are only differentially methylated in females, and 2,183 genes that are only differentially methylated in males, with 1,365 differentially methylated genes shared between females and males (Figure 2). Gene ontological analyses identified significant enrichment of pathways related to glutamate receptor and ion channel activity in shared gene sets (Figure 3). Conclusion: 33,732 unique, sex‐specific DMPs in AD were identified with more than 60% annotated to one of 5,067 genes. DMP‐associated genes have sex‐specific DNA methylation levels suggesting that these DMPs may play a role in the biased pathogenesis of AD. [ABSTRACT FROM AUTHOR]

In mammals, the molecular mechanisms underlying transgenerational inheritance of phenotypic traits in serial generations of progeny after ancestral environmental exposures, without variation in DNA sequence, remain elusive. We've recently described transmission of a beneficial trait in rats and mice, in which F0 supplementation of methyl donors, including folic acid, generates enhanced axon regeneration after sharp spinal cord injury in untreated F1 to F3 progeny linked to differential DNA methylation levels in spinal cord tissue. To test whether the transgenerational effect of folic acid is transmitted via the germline, we performed whole-genome methylation sequencing on sperm DNA from F0 mice treated with either folic acid or vehicle control, and their F1, F2, and F3 untreated progeny. Transgenerational differentially methylated regions (DMRs) are observed in each consecutive generation and distinguish folic acid from untreated lineages, predominate outside of CpG islands and in regions of the genome that regulate gene expression, including promoters, and overlap at both the differentially methylated position (DMP) and gene levels. These findings indicate that molecular changes between generations are caused by ancestral folate supplementation. In addition, 29,719 DMPs exhibit serial increases or decreases in DNA methylation levels in successive generations of untreated offspring, correlating with a serial increase in the phenotype across generations, consistent with a 'wash-in' effect. Sibship-specific DMPs annotate to genes that participate in axon- and synapse-related pathways. [ABSTRACT FROM AUTHOR]

Background: DNA microarray‐based studies report differentially methylated positions (DMPs) in blood between cognitively unimpaired persons (CU) and persons with late‐onset dementia due to Alzheimer's disease (AD) or Mild Cognitive Impairment (MCI) but interrogate less than 4% of the human genome. Whole genome methylation sequencing (WGMS) quantifies DNA methylation levels across the entire human genome (>25 million CpG loci). Using WGMS, we previously reported 28,038 DMPs within 2,707 genes between persons with and without AD. Method: We used WGMS to measure DNA methylation levels in nuclear genes encoding proteins that participate in mitochondrial function as cataloged in the Human Protein Atlas in blood samples from participants with AD (N = 109) and MCI (N = 99) compared to CU (N = 174). DNA methylation levels were compared cross‐sectionally in the Wisconsin Alzheimer's Disease Research Center (WADRC) and the Wisconsin Registry for Alzheimer's Prevention (WRAP) cohorts. ParticipantAPOE allele and demographic information are provided in Table 1. Result: Mitochondrial‐related genes (N = 1,121) were differentially methylated (local false discovery rate [lFDR] < 0.01) in persons with AD (N = 218) and MCI (N = 421) compared to CU controls. Gene ontology pathway analyses of differentially methylated genes observed in both AD and MCI groups (N = 142) are enriched for multiple terms, including myristoyl‐CoA hydrolase, palmitoyl‐CoA hydrolase, and thiolester hydrolase activity (Figure 1). Differentially methylated genes align with differentially expressed genes that support beta‐oxidation (acyl‐CoA dehydrogenase family member 9 [ACAD9]) and fatty acid transport into mitochondria (carnitine palmitoyl transferase I [CPT1A]) in blood from persons with AD. Conclusion: Disordered pathways that participate in beta‐oxidation and fatty acid metabolism have been identified in large‐scale multi‐omic reports of AD histopathology. Present data indicate that corresponding changes in the methylome play a role in mitochondrial pathways known to contribute to the pathogenesis of AD and may serve as candidates for diagnosis and intervention. [ABSTRACT FROM AUTHOR]

Children with an anxious temperament (AT) are at a substantially increased risk to develop anxiety and depression. The young rhesus monkey is ideal for studying the origin of human AT because it shares with humans the genetic, neural, and phenotypic underpinnings of complex social and emotional functioning. Heritability, functional imaging, and gene expression studies of AT in young monkeys revealed that the central nucleus of the amygdala (Ce) is a key environmentally sensitive substrate of this at risk phenotype. Because epigenetic marks (e.g., DNA methylation) can be modulated by environmental stimuli, these data led us to hypothesize a role for DNA methylation in the development of AT. To test this hypothesis, we used reduced representation bisulfite sequencing to examine the cross-sectional genome-wide methylation levels in the Ce of 23 age-matched monkeys (1.3 ± 0.2 years) phenotyped for AT. Because AT reflects a continuous trait-like variable, we used an analytical approach that is consistent with this biology to identify genes in the Ce with methylation patterns that predict AT. Expression data from the Ce of these same monkeys were then used to find differentially methylated candidates linked to altered gene regulation. Two genes particularly relevant to the AT phenotype were BCL11A and JAG1. These transcripts have well-defined roles in neurodevelopmental processes, including neurite arborization and the regulation of neurogenesis. Together, these findings represent a critical step toward understanding the effects of early environment on the neuromolecular mechanisms that underlie the risk to develop anxiety and depressive disorders.

INTRODUCTION: DNA microarray‐based studies report differentially methylated positions (DMPs) in blood between late‐onset dementia due to Alzheimer's disease (AD) and cognitively unimpaired individuals, but interrogate < 4% of the genome. METHODS: We used whole genome methylation sequencing (WGMS) to quantify DNA methylation levels at 25,409,826 CpG loci in 281 blood samples from 108 AD and 173 cognitively unimpaired individuals. RESULTS: WGMS identified 28,038 DMPs throughout the human methylome, including 2707 differentially methylated genes (e.g., SORCS3, GABA, and PICALM) encoding proteins in biological pathways relevant to AD such as synaptic membrane, cation channel complex, and glutamatergic synapse. One hundred seventy‐three differentially methylated blood‐specific enhancers interact with the promoters of 95 genes that are differentially expressed in blood from persons with and without AD. DISCUSSION: WGMS identifies differentially methylated CpGs in known and newly detected genes and enhancers in blood from persons with and without AD. Highlights: Whole genome DNA methylation levels were quantified in blood from persons with and without Alzheimer's disease (AD).Twenty‐eight thousand thirty‐eight differentially methylated positions (DMPs) were identified.Two thousand seven hundred seven genes comprise DMPs.Forty‐eight of 75 independent genetic risk loci for AD have DMPs.One thousand five hundred sixty‐eight blood‐specific enhancers comprise DMPs, 173 of which interact with the promoters of 95 genes that are differentially expressed in blood from persons with and without AD. [ABSTRACT FROM AUTHOR]

Orofacial clefts of the lip and palate are widely recognized to result from complex gene- environment interactions, but inadequate understanding of environmental risk factors has stymied development of prevention strategies. We interrogated the role of DNA methylation, an environmentally malleable epigenetic mechanism, in orofacial development. Expression of the key DNA methyltransferase enzyme DNMT1 was detected throughout palate morphogenesis in the epithelium and underlying cranial neural crest cell (cNCC) mesenchyme, a highly proliferative multipotent stem cell population that forms orofacial connective tissue. Genetic and pharmacologic manipulations of DNMT activity were then applied to define the tissue-and timing-dependent requirement of DNA methylation in orofacial development. cNCC-specific Dnmt1 inactivation targeting initial palate outgrowth resulted in OFCs, while later targeting during palatal shelf elevation and elongation did not. Conditional Dnmt1 deletion reduced cNCC proliferation and subsequent differentiation trajectory, resulting in attenuated outgrowth of the palatal shelves and altered development of cNCC-derived skeletal elements. Finally, we found that the cellular mechanisms of cleft pathogenesis observed in vivo can be recapitulated by pharmacologically reducing DNA methylation in multipotent cNCCs cultured in vitro. These findings demonstrate that DNA methylation is a crucial epigenetic regulator of cNCC biology, define a critical period of development in which its disruption directly causes OFCs, and provide opportunities to identify environmental influences that contribute to OFC risk. [ABSTRACT FROM AUTHOR]

Over the last years, the use of peripheral blood-derived big datasets in combination with machine learning technology has accelerated the understanding, prediction, and management of pulmonary and critical care conditions. The goal of this article is to provide readers with an introduction to the methods and applications of blood omics and other multiplex-based technologies in the pulmonary and critical care medicine setting to better appreciate the current literature in the field. To accomplish that, we provide essential concepts needed to rationalize this approach and introduce readers to the types of molecules that can be obtained from the circulating blood to generate big datasets; elaborate on the differences between bulk, sorted, and single-cell approaches; and the basic analytical pipelines required for clinical interpretation. Examples of peripheral blood-derived big datasets used in recent literature are presented, and limitations of that technology are highlighted to qualify both the current and future value of these methodologies. [ABSTRACT FROM AUTHOR]

Treatment with rapamycin, an inhibitor of the mechanistic Target Of Rapamycin Complex One (mTORC1) protein kinase, has been repeatedly demonstrated to extend lifespan and prevent or delay age-related diseases in diverse model systems. Concerns over the risk of potentially serious side effects in humans, including immunosuppression and metabolic disruptions, have cautiously limited the translation of rapamycin and its analogs as a treatment for aging associated conditions. During the last decade, we and others have developed a working model that suggests that while inhibition of mTORC1 promotes healthy aging, many of the negative side effects of rapamycin are associated with "off-target" inhibition of a second mTOR complex, mTORC2. Differences in the kinetics and molecular mechanisms by which rapamycin inhibits mTORC1 and mTORC2 suggest that a therapeutic window for rapamycin could be exploited using intermittent dosing schedules or alternative rapalogs that may enable more selective inhibition of mTORC1. However, the optimal dosing schedules and the long-term efficacy of such interventions in humans are unknown. Here, we highlight ongoing or upcoming clinical trials that will address outstanding questions regarding the safety, pharmacokinetics, pharmacodynamics, and efficacy of rapamycin and rapalogs on several clinically oriented outcomes. Results from these early phase studies will help guide the design of phase 3 clinical trials to determine whether rapamycin can be used safely to inhibit mTORC1 for the treatment and prevention of age-related diseases in humans. [ABSTRACT FROM AUTHOR]

Background: Age is the most significant predictor of Alzheimer's disease and related dementias (ADRD). Biological age, in contrast to chronological age, is modifiable – shaped by environmental and social factors which contribute to the functional declines observed in aging. Accelerated biological aging has been observed in historically underrepresented populations in ADRD research who are at highest risk for developing ADRD. Telomere length (TL) is a marker of biological age and empirically associated with cognitive aging. However, this association has not been investigated in historically underrepresented populations such as American Indians / Alaska Natives (AI/AN). This study reports on the utility of TL to predict cognitive performance in a sample of middle‐aged and older adults from Wisconsin communities historically underrepresented in ADRD research. Method: The Wisconsin Alzheimer's Disease Research Center's (WADRC) Inclusion of Underrepresented Groups Core engages AI/AN, Blacks / African Americans (B/AA), and participants of multi‐race and ethnicity identities through community based participatory research practices. A sample (n = 188) identifying their race as AI/AN or B/AA were included if they provided whole blood and completed the Rey Auditory Verbal Learning Test (RAVLT, Trials 1‐5) and the Trails Making Test (TMT, A and B times) for verbal learning and executive functioning, respectively. DNA was extracted from whole blood and analyzed with monochrome multiplex quantitative polymerase chain reaction for TL. Multivariable linear regression analyses tested relationships between TL and cognitive test performance. Result: The participants (mean age = 60.88 ±9.06) were majority female, with 79.26% B/AA and 12.77% AI/AN (Table 1). In bivariate analyses, TL significantly correlated with all outcomes: longer telomeres correlated with better verbal learning and executive functioning performance (Figure 1A‐C). In multivariable regression models, TL significantly predicted cognitive performance for all outcomes independent of participant sex, race, age, and cognitive status (Table 2). Conclusion: These findings suggest that TL is a strong predictor of cognitive performance for historically underrepresented populations, offering potential opportunities for screening of accelerated biological aging and interventions. The community‐led research at the WADRC makes this analysis the first of its kind to include AI/AN participants. Future ADRD research should consider behavioral and socioeconomic interventions shown to modify biological aging. [ABSTRACT FROM AUTHOR]

Human epidemiological studies reveal that dietary and environmental alterations influence the health of the offspring and that the effect is not limited to the F1 or F2 generations. Non-Mendelian transgenerational inheritance of traits in response to environmental stimuli has been confirmed in non-mammalian organisms including plants and worms and are shown to be epigenetically mediated. However, transgenerational inheritance beyond the F2 generation remains controversial in mammals. Our lab previously discovered that the treatment of rodents (rats and mice) with folic acid significantly enhances the regeneration of injured axons following spinal cord injury in vivo and in vitro , and the effect is mediated by DNA methylation. The potential heritability of DNA methylation prompted us to investigate the following question: Is the enhanced axonal regeneration phenotype inherited transgenerationally without exposure to folic acid supplementation in the intervening generations? In the present review, we condense our findings showing that a beneficial trait (i.e. enhanced axonal regeneration after spinal cord injury) and accompanying molecular alterations (i.e. DNA methylation), triggered by an environmental exposure (i.e. folic acid supplementation) to F0 animals only, are inherited transgenerationally and beyond the F3 generation. [ABSTRACT FROM AUTHOR]

Maternal malnutrition remains one of the major adversities affecting brain development and long-term mental health outcomes, increasing the risk to develop anxiety and depressive disorders. We have previously shown that malnutrition-induced anxiety-like behaviours can be rescued by a social and sensory stimulation (enriched environment) in male mice. Here, we expand these findings to adult female mice and profiled genome-wide ventral hippocampal 5hmC levels related to malnutrition-induced anxiety-like behaviours and their rescue by an enriched environment. This approach revealed 508 differentially hydroxymethylated genes associated with protein malnutrition and that several genes (N = 34) exhibited a restored 5hmC abundance to control levels following exposure to an enriched environment, including genes involved in neuronal functions like dendrite outgrowth, axon guidance, and maintenance of neuronal circuits (e.g. Fltr3, Itsn1, Lman1, Lsamp, Nav, and Ror1) and epigenetic mechanisms (e.g. Hdac9 and Dicer1). Sequence motif predictions indicated that 5hmC may be modulating the binding of transcription factors for several of these transcripts, suggesting a regulatory role for 5hmC in response to perinatal malnutrition and exposure to an enriched environment. Together, these findings establish a role for 5hmC in early-life malnutrition and reveal genes linked to malnutrition-induced anxious behaviours that are mitigated by an enriched environment. [ABSTRACT FROM AUTHOR]

Alterations in environmentally sensitive epigenetic mechanisms (e.g., DNA methylation) influence axonal regeneration in the spinal cord following sharp injury. Conventional DNA methylation detection methods using sodium bisulphite treatment do not distinguish between methylated and hydroxymethylated forms of cytosine, meaning that past studies report a composite of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC). To identify the distinct contributions of DNA methylation modifications to axonal regeneration, we collected spinal cord tissue after sharp injury from untreated adult F3 male rats with enhanced regeneration of injured spinal axons or controls, derived from folate- or water-treated F0 lineages, respectively. Genomic DNA was profiled for genome-wide 5hmC levels, revealing 658 differentially hydroxymethylated regions (DhMRs). Genomic profiling with whole genome bisulphite sequencing disclosed regeneration-related alterations in composite 5mC + 5hmC DNA methylation levels at 2,260 differentially methylated regions (DMRs). While pathway analyses revealed that differentially hydroxymethylated and methylated genes are linked to biologically relevant axon developmental pathways, only 22 genes harbour both DhMR and DMRs. Since these differential modifications were more than 60 kilobases on average away from each other, the large majority of differential hydroxymethylated and methylated regions are unique with distinct functions in the axonal regeneration phenotype. These data highlight the importance of distinguishing independent contributions of 5mC and 5hmC levels in the central nervous system, and denote discrete roles for DNA methylation modifications in spinal cord injury and regeneration in the context of transgenerational inheritance. [ABSTRACT FROM AUTHOR]

Differentially methylated positions (DMPs) between persons with and without late-onset Alzheimer's disease (LOAD) were observed at 477 of 769,190 loci in a plurality of genes. Of these, 17 were shared with DMPs identified using clinical LOAD markers analyzed independently as continuous variables comprising Rey Auditory Verbal Learning Test scores, cerebrospinal fluid total tau (t-tau) and phosphorylated tau 181 (p-tau181) levels, and t-tau/Aβ1-42 (Aβ42), p-tau181/Aβ42, and Aβ42/Aβ1-40 (Aβ40) ratios. In patients with LOAD, 12 of the shared 17 DMPs were hypomethylated in B3GALT4 (Beta-1,3-galatcosyltransferase 4) (EC 2.4.1.62), and 5 were hypomethylated in ZADH2 (Prostaglandin reductase 3) (EC 1.3.1.48). [ABSTRACT FROM AUTHOR]

Human evolution from non-human primates has seen substantial change in the central nervous system, with the molecular mechanisms underlying human brain evolution remaining largely unknown. Methylation of cytosine at the fifth carbon (5-methylcytosine; 5mC) is an essential epigeneticmark linked to neurodevelopment, as well as neurological disease. The emergence of another modified form of cytosine (5-hydroxymethylcytosine; 5 hmC) that is enriched in the brain further substantiates a role for these epigenetic marks in neurodevelopment, yet little is known about the evolutionary importance of thesemarks in brain development. Here, human and monkey brain tissue were profiled, identifying 5,516 and 4,070 loci that were differentially methylated and hydroxymethylated, respectively, between the species. Annotation of these loci to the human genome revealed genes critical for the development of the nervous system and that are associated with intelligence and higher cognitive functioning, such as RELN and GNAS. Moreover, ontological analyses of these differentially methylated and hydroxymethylated genes revealed a significant enrichment of neuronal/immunological-related processes, including neurogenesis and axon development. Finally, the sequences flanking the differentially methylated/hydroxymethylated loci contained a significant enrichment of binding sites for neurodevelopmentally important transcription factors (e.g., OTX1 and PITX1), suggesting that DNA methylation may regulate gene expression by mediating transcription factor binding on these transcripts. Together, these data support dynamic species-specific epigenetic contributions in the evolution and development of the human brain from non-human primates. [ABSTRACT FROM AUTHOR]

Environmental stress contributes to the development of psychiatric disorders, including posttraumatic stress disorder and anxiety. While even acute stress alters gene expression, the molecular mechanisms underlying these changes remain largely unknown. 5-hydroxymethylcytosine (5hmC) is a novel environmentally sensitive DNA modification that is highly enriched in the brain and is associated with active transcription of neuronal genes. Here we examined behavioral and molecular alterations in adult mice that experienced an early-life stress before weaning (postnatal day 12 to 18) and found anxiety-like behaviors in adult female mice that were accompanied by correlated disruptions of hypothalamic 5hmC and gene expression in 118 genes, revealing potentially functional 5hmC (i.e., gene regulation). These genes are known and potentially novel stress-related targets, includingNr3c2, Nrxn1, Nfia, andClip1, that have a significant enrichment for neuronal ontological functions, such as neuronal development and differentiation. Sequence motif predictions indicated that 5hmC may regulate gene expression by mediating transcription factor binding and alternative splicing of many of these transcripts. Together, these findings represent a critical step toward understanding the effects of early environment on the neuromolecular mechanisms that underlie the risk to develop anxiety disorders. [ABSTRACT FROM PUBLISHER]

Background Methylation on the fifth position of cytosine (5-mC) is an essential epigenetic mark that is linked to both normal neurodevelopment and neurological diseases. The recent identification of another modified form of cytosine, 5-hydroxymethylcytosine (5-hmC), in both stem cells and post-mitotic neurons, raises new questions as to the role of this base in mediating epigenetic effects. Genomic studies of these marks using model systems are limited, particularly with array-based tools, because the standard method of detecting DNA methylation cannot distinguish between 5-mC and 5-hmC and most methods have been developed to only survey the human genome. Results We show that non-human data generated using the optimization of a widely used human DNA methylation array, designed only to detect 5-mC, reproducibly distinguishes tissue types within and between chimpanzee, rhesus, and mouse, with correlations near the human DNA level (R2 > 0.99). Genome-wide methylation analysis, using this approach, reveals 6,102 differentially methylated loci between rhesus placental and fetal tissues with pathways analysis significantly overrepresented for developmental processes. Restricting the analysis to oncogenes and tumor suppressor genes finds 76 differentially methylated loci, suggesting that rhesus placental tissue carries a cancer epigenetic signature. Similarly, adapting the assay to detect 5-hmC finds highly reproducible 5-hmC levels within human, rhesus, and mouse brain tissue that is species-specific with a hierarchical abundance among the three species (human > rhesus >> mouse). Annotation of 5-hmC with respect to gene structure reveals a significant prevalence in the 3'UTR and an association with chromatin-related ontological terms, suggesting an epigenetic feedback loop mechanism for 5-hmC. Conclusions Together, these data show that this array-based methylation assay is generalizable to all mammals for the detection of both 5-mC and 5-hmC, greatly improving the utility of mammalian model systems to study the role of epigenetics in human health, disease, and evolution. [ABSTRACT FROM AUTHOR]

Background: Fragile X syndrome (FXS) is a common form of inherited intellectual disability caused by an expansion of CGG repeats located in the 5' untranslated region (UTR) of the FMR1 gene, which leads to hypermethylation and silencing of this locus. Although a dramatic increase in DNA methylation of the FMR1 full mutation allele is well documented, the extent to which these changes affect DNA methylation throughout the rest of the genome has gone unexplored. Methods: Here we examined genome-wide methylation in both peripheral blood (N = 62) and induced pluripotent stem cells (iPSCs; N = 10) from FXS individuals and controls. Results: We not only found the expected significant DNA methylation differences in the FMR1 promoter and 50 UTR, we also saw that these changes inverse in the FMR1 gene body. Importantly, we found no other differentially methylated loci throughout the remainder of the genome, indicating the aberrant methylation of FMR1 in FXS is locus-specific. Conclusions: This study provides a comprehensive methylation profile of FXS and helps refine our understanding of the mechanisms behind FMR1 silencing. [ABSTRACT FROM AUTHOR]

Mammalian Argonaute proteins (EIF2C1-4) play an essential role in RNA-induced silencing. Here, we show that the loss of eIF2C2 (Argonaute2 or Ago2) results in gastrulation arrest, ectopic expression of Brachyury (T), and mesoderm expansion. We identify a genetic interaction between Ago2 and T, as Ago2 haploinsufficiency partially rescues the classic T/+ short-tail phenotype. Finally, we demonstrate that the ectopic T expression and concomitant mesoderm expansion result from disrupted fibroblast growth factor signaling, likely due to aberrant expression of Eomesodermin. Together, these data indicate that a factor best known as a key component of the RNA-induced silencing complex is required for proper fibroblast growth factor signaling during gastrulation, suggesting a possible micro-RNA function in the formation of a mammalian germ layer. [ABSTRACT FROM AUTHOR]

Long Interspersed Element-1 (LINE-1 or L1) retrotransposons encode proteins required for their mobility (ORF1p and ORF2p), yet little is known about how L1 mRNA is translated. Here, we show that ORF2 translation generally initiates from the first in-frame methionine codon of ORF2, and that both ORF1 and the inter-ORF spacer are dispensable for ORF2 translation. Remarkably, changing the ORF2 AUG codon to any other coding triplet is compatible with retrotransposition. However, introducing a premature termination codon in ORF1 or a thermostable hairpin in the inter-ORF spacer reduces ORF2p translation or L1 retrotransposition to ∼5% of wild-type levels. Similar data obtained from "natural" and codon optimized "synthetic" mouse L1s lead us to propose that ORF2 is translated by an unconventional termination/ reinitiation mechanism. [ABSTRACT FROM AUTHOR]

Fragile X syndrome is caused by the loss of an RNA-binding protein called FMRP (for fragile X mental retardation protein). FMRP seems to influence synaptic plasticity through its role in mRNA transport and translational regulation. Recent advances include the identification of mRNA ligands, FMRP-mediated mRNA transport and the neuronal consequence of FMRP deficiency. FMRP was also recently linked to the microRNA pathway. These advances provide mechanistic insight into this disorder, and into learning and memory in general. [ABSTRACT FROM AUTHOR]

DNA methylation (DNAm) plays diverse roles in human biology, but this dynamic epigenetic mark remains far from fully characterized. Although earlier studies uncovered loci that undergo age-associated DNAm changes in adults, little is known about such changes during childhood. Despite profound DNAm plasticity during embryogenesis, monozygotic twins show indistinguishable childhood methylation, suggesting that DNAm is highly coordinated throughout early development. Here we examine the methylation of 27,578 CpG dinucleotides in peripheral blood DNA from a cross-sectional study of 398 boys, aged 3"17 yr, and find significant ageassociated changes in DNAm at 2078 loci. These findings correspond well with pyrosequencing data and replicate in a second pediatric population (N = 78). Moreover, we report a deficit of age-related loci on the X chromosome, a preference for specific nucleotides immediately surrounding the interrogated CpG dinucleotide, and a primary association with developmental and immune ontological functions. Meta-analysis (N = 1158) with two adult populations reveals that despite a significant overlap of age-associated loci, most methylation changes do not follow a lifelong linear pattern due to a threefold to fourfold higher rate of change in children compared with adults; consequently, the vast majority of changes are more accurately modeled as a function of logarithmic age. We therefore conclude that age-related DNAm changes in peripheral blood occur more rapidly during childhood and are imperfectly accounted for by statistical corrections that are linear in age, further suggesting that future DNAm studies should be matched closely for age. [ABSTRACT FROM AUTHOR]

Introduction: Whole genome methylation sequencing (WGMS) in blood identifies differential DNA methylation in persons with late-onset dementia due to Alzheimer's disease (AD) but has not been tested in persons with mild cognitive impairment (MCI)., Methods: We used WGMS to compare DNA methylation levels at 25,244,219 CpG loci in 382 blood samples from 99 persons with MCI, 109 with AD, and 174 who are cognitively unimpaired (CU)., Results: WGMS identified 9756 differentially methylated positions (DMPs) in persons with MCI, including 1743 differentially methylated genes encoding proteins in biological pathways related to synapse organization, dendrite development, and ion transport. A total of 447 DMPs exhibit progressively increasing or decreasing DNA methylation levels among CU, MCI, and AD that correspond to cognitive status., Discussion: WGMS identifies DMPs in known and newly detected genes in blood from persons with MCI and AD that support blood DNA methylation levels can distinguish cognitive status., Highlights: Whole genome methylation levels in blood from 99 persons with mild cognitive impairment (MCI), 109 with Alzheimer's disease, and 174 who are cognitively unimpaired were analyzed. Nine thousand seven hundred fifty-six differentially methylated positions (DMPs) were identified in MCI. One thousand seven hundred forty-three genes comprise one or more DMPs in persons with MCI. Fifty-eight DMPs and 392 differentially methylated genes are shared among the three pairwise comparisons. Four hundred forty-seven DMPs exhibit progressive changes that correspond to cognitive status., (© 2024 The Author(s). Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)

Objective: Accelerated biological aging is a plausible and modifiable determinant of dementia burden facing minoritized communities, but is not well-studied in these historically underrepresented populations. Our objective was to preliminarily characterize relationships between telomere length and cognitive health among American Indian/Alaska Native (AI/AN) and Black/African American (B/AA) middle-aged and older adults., Methods: This study included data on telomere length and cognitive test performance from 187 participants, enrolled in one of two community-based cognitive aging cohorts and who identified their primary race as AI/AN or B/AA., Results: Nested multivariable regression models revealed preliminary evidence for associations between telomere length and cognitive performance, and these associations were partially independent of chronological age., Discussion: Small sample size limited estimate precision, however, findings suggest future work on telomere length and cognitive health in underrepresented populations at high risk for dementia is feasible and valuable as a foundation for social and behavioral intervention research.