Base-resolution analysis of 5-hydroxymethylcytosine in the mammalian genome.

The study of 5-hydroxylmethylcytosines (5hmC) has been hampered by the lack of a method to map it at single-base resolution on a genome-wide scale. Affinity purification-based methods cannot precisely locate 5hmC nor accurately determine its relative abundance at each modified site. We here present a genome-wide approach, Tet-assisted bisulfite sequencing (TAB-Seq), that when combined with traditional bisulfite sequencing can be used for mapping 5hmC at base resolution and quantifying the relative abundance of 5hmC as well as 5mC. Application of this method to embryonic stem cells not only confirms widespread distribution of 5hmC in the mammalian genome but also reveals sequence bias and strand asymmetry at 5hmC sites. We observe high levels of 5hmC and reciprocally low levels of 5mC near but not on transcription factor-binding sites. Additionally, the relative abundance of 5hmC varies significantly among distinct functional sequence elements, suggesting different mechanisms for 5hmC deposition and maintenance.

Efr3b is essential for social recognition by modulating the excitability of CA2 pyramidal neurons.

CA2 pyramidal neurons (PNs) are associated with social behaviors. The mechanisms, however, remain to be fully investigated. Here, we report that Efr3b, a protein essential for phospholipid metabolism at the plasma membrane, is widely expressed in the brain, especially in the hippocampal CA2/CA3 areas. To assess the functional significance of Efr3b in the brain, we generated Efr3bf/f mice and crossed them with Nestin-cre mice to delete Efr3b specifically in the brain. We find that Efr3b deficiency in the brain leads to deficits of social novelty recognition and hypoexcitability of CA2 PNs. We then knocked down the expression of Efr3b specifically in CA2 PNs of C57BL/6J mice, and our results showed that reducing Efr3b in CA2 PNs also resulted in deficits of social novelty recognition and hypoexcitability of CA2 PNs. More interestingly, restoring the expression of Efr3b in CA2 PNs enhances their excitability and improves social novelty recognition in Efr3b-deficient mice. Furthermore, direct activation of CA2 PNs with chemogenetics improves social behaviors in Efr3b-deficient mice. Together, our data suggest that Efr3b is essential for social novelty by modulating the excitability of CA2 PNs.

Ogt Deficiency Induces Abnormal Cerebellar Function and Behavioral Deficits of Adult Mice through Modulating RhoA/ROCK Signaling.

Previous studies have shown the essential roles of O-GlcNAc transferase (Ogt) and O-GlcNAcylation in neuronal development, function and neurologic diseases. However, the function of Ogt and O-GlcNAcylation in the adult cerebellum has not been well elucidated. Here, we have found that cerebellum has the highest level of O-GlcNAcylation relative to cortex and hippocampus of adult male mice. Specific deletion of Ogt in granule neuron precursors (GNPs) induces abnormal morphology and decreased size of the cerebellum in adult male Ogt deficient [conditional knock-out (cKO)] mice. Adult male cKO mice show the reduced density and aberrant distribution of cerebellar granule cells (CGCs), the disrupted arrangement of Bergman glia (BG) and Purkinje cells. In addition, adult male cKO mice exhibit aberrant synaptic connection, impaired motor coordination, and learning and memory abilities. Mechanistically, we have identified G-protein subunit α12 (Gα12) is modified by Ogt-mediated O-GlcNAcylation. O-GlcNAcylation of Gα12 facilitates its binding to Rho guanine nucleotide exchange factor 12 (Arhgef12) and consequently activates RhoA/ROCK signaling. RhoA/ROCK pathway activator LPA can rescue the developmental deficits of Ogt deficient CGCs. Therefore, our study has revealed the critical function and related mechanisms of Ogt and O-GlcNAcylation in the cerebellum of adult male mice.SIGNIFICANCE STATEMENT Cerebellar function are regulated by diverse mechanisms. To unveil novel mechanisms is critical for understanding the cerebellar function and the clinical therapy of cerebellum-related diseases. In the present study, we have shown that O-GlcNAc transferase gene (Ogt) deletion induces abnormal cerebellar morphology, synaptic connection, and behavioral deficits of adult male mice. Mechanistically, Ogt catalyzes O-GlcNAcylation of Gα12, which promotes the binding to Arhgef12, and regulates RhoA/ROCK signaling pathway. Our study has uncovered the important roles of Ogt and O-GlcNAcylation in regulating cerebellar function and cerebellum-related behavior. Our results suggest that Ogt and O-GlcNAcylation could be potential targets for some cerebellum-related diseases.

The influence of resourcefulness on the family functioning of young- and middle-aged lymphoma patients in China: a cross-sectional study.

BACKGROUND: Lymphoma has become 1 of the 10 most common cancers with increased prevalence in young- and middle-aged adults in China. This poses a tremendous burden on patients and their families and brings great challenges to maintaining the balance of family functioning in young- and middle-aged patients. OBJECTIVE: This cross-sectional study aimed to analyse the influence of resourcefulness on the family functioning of Chinese young- and middle-aged lymphoma patients. METHODS: A total of 172 Chinese young- and middle-aged patients with lymphoma were recruited from the oncology departments of two tertiary hospitals in Zhengzhou, Henan, China. They were invited to complete a survey that included a demographic questionnaire, the Resourcefulness Scale and the Chinese Version Family Adaptability and Cohesion Scale II. Multiple linear regression was used to analyse the related factors for family functioning. RESULTS: The multiple regression analysis revealed that the main influencing factors of family cohesion were resourcefulness (ß = 0.338, 95% CI (0.072, 0.173)), spouse caregiver (ß = 0.376, 95% CI (1.938, 10.395)), and cancer stage (ß = -0.274, 95% CI (-3.219, -1.047)). Resourcefulness (ß = 0.438, 95% CI (0.096, 0.181)), spouse caregiver (ß = 0.340, 95% CI (1.348, 8.363)), and family per capita monthly income (ß = 0.157, 95% CI (0.066, 2.243)) were the influencing factors of family adaptability. CONCLUSIONS: Healthcare professionals and family scholars should value young- and middle-aged lymphoma patients' family functioning throughout the cancer treatment process, and family interventions should be designed by healthcare providers based on patients' resourcefulness. Moreover, healthcare providers need to pay attention to the risk factors of patients' family cohesion and adaptability, such as low family per capita monthly income, and consider employing corresponding measures to help them.

OGT-1 regulates synaptic assembly through the insulin signaling pathway.

The formation and maintenance of synapses are precisely regulated, and the misregulation often leads to neurodevelopmental or neurodegenerative disorders. Besides intrinsic genetically encoded signaling pathways, synaptic structure and function are also regulated by extrinsic factors, such as nutrients. O-GlcNAc transferase (OGT), a nutrient sensor, is abundant in the nervous system and required for synaptic plasticity, learning, and memory. However, whether OGT is involved in synaptic development and the mechanism underlying the process are largely unknown. In this study, we found that OGT-1, the OGT homolog in C. elegans, regulates the presynaptic assembly in AIY interneurons. The insulin receptor DAF-2 acts upstream of OGT-1 to promote the presynaptic assembly by positively regulating the expression of ogt-1. This insulin-OGT-1 axis functions most likely by regulating neuronal activity. In this study, we elucidated a novel mechanism for synaptic development, and provided a potential link between synaptic development and insulin-related neurological disorders.

O-GlcNAc transferase Ogt regulates embryonic neuronal development through modulating Wnt/ß-catenin signaling.

Ogt-mediated O-GlcNAcylation is enriched in the nervous system and involves in neuronal development, brain function and neurological diseases. However, the roles of Ogt and O-GlcNAcylation in embryonic neurogenesis have remained largely unknown. Here, we show that Ogt is highly expressed in embryonic brain, and Ogt depletion reduces the proliferation of embryonic neural stem cells and migration of new born neurons. Ogt depletion in cultured hippocampal neurons impairs neuronal maturation, including reduced dendritic numbers and length, and immature development of spines. Mechanistically, Ogt depletion decreases the activity of Wnt/ß-catenin signaling. Ectopic ß-catenin rescues neuronal developmental deficits caused by Ogt depletion. Ogt also regulates human cortical neurogenesis in forebrain organoids derived from induced pluripotent stem cells. Our findings reveal the essential roles and mechanisms of Ogt-mediated O-GlcNAc modification in regulating mammalian neuronal development.

Loss of ten-eleven translocation 2 induces cardiac hypertrophy and fibrosis through modulating ERK signaling pathway.

The ten-eleven translocation (Tet) family of dioxygenases convert 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). Previous studies have shown that 5hmC-mediated epigenetic modifications play essential roles in diverse biological processes and diseases. Here, we show that Tet proteins and 5hmC display dynamic features during postnatal cardiac development and that Tet2 is the predominant dioxygenase present in heart. Tet2 knockout results in abnormal cardiac function, progressive cardiac hypertrophy and fibrosis. Mechanistically, Tet2 deficiency leads to reduced hydroxymethylation in the cardiac genome and alters the cardiac transcriptome. Mechanistically, Tet2 loss leads to a decrease of Hspa1b expression, a regulator of the extracellular signal-regulated protein kinase (Erk) signaling pathway, which leads to over-activation of Erk signaling. Acute Hspa1b knock down (KD) increased the phosphorylation of Erk and induced hypertrophy of cardiomyocytes, which could be blocked by Erk signaling inhibitor. Consistently, ectopic expression of Hspa1b was able to rescue the deficits of cardiomyocytes induced by Tet2 depletion. Taken together, our study's results reveal the important roles of Tet2-mediated DNA hydroxymethylation in cardiac development and function.

Ogt-mediated O-GlcNAcylation inhibits astrocytes activation through modulating NF-κB signaling pathway.

Previous studies have shown that Ogt-mediated O-GlcNAcylation is essential for neuronal development and function. However, the function of O-GlcNAc transferase (Ogt) and O-GlcNAcylation in astrocytes remains largely unknown. Here we show that Ogt deficiency induces inflammatory activation of astrocytes in vivo and in vitro, and impairs cognitive function of mice. The restoration of O-GlcNAcylation via GlcNAc supplementation inhibits the activation of astrocytes, inflammation and improves the impaired cognitive function of Ogt deficient mice. Mechanistically, Ogt interacts with NF-κB p65 and catalyzes the O-GlcNAcylation of NF-κB p65 in astrocytes. Ogt deficiency induces the activation of NF-κB signaling pathway by promoting Gsk3ß binding. Moreover, Ogt depletion induces the activation of astrocytes derived from human induced pluripotent stem cells. The restoration of O-GlcNAcylation inhibits the activation of astrocytes, inflammation and reduces Aß plaque of AD mice in vitro and in vivo. Collectively, our study reveals a critical function of Ogt-mediated O-GlcNAcylation in astrocytes through regulating NF-κB signaling pathway.

O-GlcNAcylation regulates the methionine cycle to promote pluripotency of stem cells.

Methionine metabolism is critical for the maintenance of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) pluripotency. However, little is known about the regulation of the methionine cycle to sustain ESC pluripotency. Here, we show that adenosylhomocysteinase (AHCY), an important enzyme in the methionine cycle, is critical for the maintenance and differentiation of mouse embryonic stem cells (mESCs). We show that mESCs exhibit high levels of methionine metabolism, whereas decreasing methionine metabolism via depletion of AHCY promotes mESCs to differentiate into the three germ layers. AHCY is posttranslationally modified with an O-linked ß-N-acetylglucosamine sugar (O-GlcNAcylation), which is rapidly removed upon differentiation. O-GlcNAcylation of threonine 136 on AHCY increases its activity and is important for the maintenance of trimethylation of histone H3 lysine 4 (H3K4me3) to sustain mESC pluripotency. Blocking glycosylation of AHCY decreases the ratio of S-adenosylmethionine versus S-adenosylhomocysteine (SAM/SAH), reduces the level of H3K4me3, and poises mESC for differentiation. In addition, blocking glycosylation of AHCY reduces somatic cell reprogramming. Thus, our findings reveal a critical role of AHCY and a mechanistic understanding of O-glycosylation in regulating ESC pluripotency and differentiation.

Dynamic effects of Fto in regulating the proliferation and differentiation of adult neural stem cells of mice.

N 6-methyladenosine (m6A) modification of RNA is deposited by the methyltransferase complex consisting of Mettl3 and Mettl14 and erased by demethylase Fto and Alkbh5 and is involved in diverse biological processes. However, it remains largely unknown the specific function and mechanism of Fto in regulating adult neural stem cells (aNSCs). In the present study, utilizing a conditional knockout (cKO) mouse model, we show that the specific ablation of Fto in aNSCs transiently increases the proliferation of aNSCs and promotes neuronal differentiation both in vitro and in vivo, but in a long term, the specific ablation of Fto inhibits adult neurogenesis and neuronal development. Mechanistically, Fto deficiency results in a significant increase in m6A modification in Pdgfra and Socs5. The increased expression of Pdgfra and decreased expression of Socs5 synergistically promote the phosphorylation of Stat3. The modulation of Pdgfra and Socs5 can rescue the neurogenic deficits induced by Fto depletion. Our results together reveal an important function of Fto in regulating aNSCs through modulating Pdgfra/Socs5-Stat3 pathway.

Fto-modulated lipid niche regulates adult neurogenesis through modulating adenosine metabolism.

Adult neurogenesis is regulated by diverse factors including the local environment, i.e. the neurogenic niche. However, whether the lipid in the brain regulates adult neurogenesis and related mechanisms remains largely unknown. In the present study, we found that lipid accumulates in the brain during postnatal neuronal development. Conditional knockout of Fto (cKO) in lipid not only reduced the level of lipid in the brain but also impaired the learning and memory of mice. In addition, Fto deficiency in lipid did not affect the proliferation of adult neural stem cells (aNSCs), but it did inhibit adult neurogenesis by inducing cell apoptosis. Mechanistically, specific deleting Fto in lipid altered gene expression and increased adenosine secretion of adipocytes. The treatment of adenosine promoted the apoptosis of newborn neurons. As a whole, these results reveal the important function of the lipid niche and its associated mechanism in regulating adult neurogenesis.

The roles of epigenetic modifications in neurodegenerative diseases.

In neuronal system, epigenetic modifications are essential for neuronal development, the fate determination of neural stem cells and neuronal function. The dysfunction of epigenetic regulation is closely related to occurrence and development of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease. Abnormally elevated DNA methylation inhibits the expression of some DNA repair-related genes and affects the progression of Huntington's disease. In the brain of Alzheimer's disease patients, the levels of H3K27ac and H3K9ac histone modifications increased. In addition, the alteration of RNA methylation in animal models of Alzheimer's disease and Parkinson's disease showed discrepancy trends. Therefore, epigenetic modifications may serve as potential therapeutic targets for neurodegenerative diseases. Here, we summarize the recent progress of the roles of epigenetic modifications in neurodegenerative diseases.

5-Hydroxymethylcytosine alterations in the human postmortem brains of autism spectrum disorder.

Autism spectrum disorders (ASDs) include a group of syndromes characterized by impaired language, social and communication skills, in addition to restrictive behaviors or stereotypes. However, with a prevalence of 1.5% in developed countries and high comorbidity rates, no clear underlying mechanism that unifies the heterogeneous phenotypes of ASD exists. 5-hydroxymethylcytosine (5hmC) is highly enriched in the brain and recognized as an essential epigenetic mark in developmental and brain disorders. To explore the role of 5hmC in ASD, we used the genomic DNA isolated from the postmortem cerebellum of both ASD patients and age-matched controls to profile genome-wide distribution of 5hmC. We identified 797 age-dependent differentially hydroxymethylated regions (DhMRs) in the young group (age ≤ 18), while no significant DhMR was identified in the groups over 18 years of age. Pathway and disease association analyses demonstrated that the intragenic DhMRs were in the genes involved in cell-cell communication and neurological disorders. Also, we saw significant 5hmC changes in the larger group of psychiatric genes. Interestingly, we found that the predicted cis functions of non-coding intergenic DhMRs strikingly associate with ASD and intellectual disorders. A significant fraction of intergenic DhMRs overlapped with topologically associating domains. These results together suggest that 5hmC alteration is associated with ASD, particularly in the early development stage, and could contribute to the pathogenesis of ASD.

Disrupted brain functional networks in patients with end-stage renal disease undergoing hemodialysis.

Patterns of change in whole-brain functional networks remain poorly understood in patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD). We conducted a prospective research to investigate the topological properties of whole-brain functional networks in those patients using a graph-based network analysis. Resting-state functional magnetic resonance imaging was performed on 51 ESRD patients (25 HD and 26 nondialysis patients) and 36 healthy controls (HCs). We compared the topological properties of brain functional networks among the three groups, and analyzed the relationships between those significant parameters and clinical variables in ESRD patients. Progressively disrupted global topological organizations were observed from nondialysis patients to HD patients compared with HCs (all p < 0.05 after Bonferroni correction). HD patients, relative to HCs, showed significantly decreased nodal centralities in the left temporal pole: superior temporal gyrus, bilateral median cingulate and paracingulate gyri, bilateral hippocampus, bilateral parahippocampal gyrus, and bilateral amygdala, and showed increased nodal centralities in the orbital part of the bilateral middle frontal gyrus, left cuneus, and left superior occipital gyrus (all p < 0.05 after Bonferroni correction). Furthermore, nodal centralities in the bilateral hippocampus were significantly decreased in HD patients compared with nondialysis patients (p < 0.05 after Bonferroni correction). Dialysis duration negatively correlated with global efficiency in ESRD patients undergoing HD (r = -0.676, FDR q = 0.004). This study indicates that ESRD patients exhibit disruptions in brain functional networks, which are more severe in HD patients, and these alterations are correlated with cognitive performance and clinical markers.

Altered Whole-Brain Functional Networks in Drug-Naïve, First-Episode Adolescents With Major Depression Disorder.

BACKGROUND: Neuroimaging studies have demonstrated disrupted brain functional networks in major depression disorder (MDD); however, alterations to whole-brain networks specifically associated with adolescent MDD remain poorly understood. PURPOSE: To investigate the topological architecture of intrinsic brain functional networks in drug-naïve, first-episode adolescent MDD patients using graph theoretical analysis. STUDY TYPE: Prospective. SUBJECTS: In all, 109 adolescent MDD patients and 70 healthy control subjects. FIELD STRENGTH/SEQUENCES: 3.0T; gradient-echo echo-planar imaging sequence. ASSESSMENT: After the construction of whole-brain functional networks by thresholding partial correlation matrices of 90 brain regions, we calculated the topological properties (eg, small-world, efficiency, and nodal centrality) using graph theoretical analysis. STATISTICAL TESTS: A chi-squared test was used to compare the gender-ratio difference, and a two-sample t-test was used in the comparison of age. We compared network measures between the two groups using nonparametric permutation tests. Exploratory partial correlation analyses were used to determine the relationships between the topological metrics showing significant between-group differences and the clinical variables for adolescent MDD patients. RESULTS: Small-world architecture in brain functional networks was identified for both the MDD and control groups. However, depressed adolescents exhibited lower characteristic path length, normalized characteristic path length and clustering coefficient, and higher global efficiency than controls (false discovery rate [FDR] q < 0.05). Compared with controls, depressed adolescents exhibited increased nodal centralities in the default mode regions, including the right anterior cingulate and paracingulate gyri, left posterior cingulate gyrus, right superior frontal gyrus (medial part), bilateral hippocampus, and bilateral parahippocampal gyrus, and decreased nodal centralities in the orbitofrontal, temporal, and occipital regions (FDR q < 0.05). DATA CONCLUSION: This study indicated that drug-naïve, first-episode adolescent MDD patients exhibit disruptions in whole-brain functional networks. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 2 J. MAGN. RESON. IMAGING 2020;52:1790-1798.

RYBP modulates stability and function of Ring1B through targeting UBE3A.

Ring1 and yin yang 1-binding protein (RYBP) are central components of noncanonical polycomb-repressive complex 1 (nc-PRC1), which represses target gene expression and is required for normal organismal development. However, the molecular function of RYBP in this complex is obscure. In this study, we showed that RYBP inhibits the polyubiquitination-mediated proteasomal degradation of Ring1B independently of its ubiquitin (Ub)-protein isopeptide ligase (E3) ligase activity, leading to its stabilization and increased catalytic activity toward monoubiquitination of histone H2A at lysine 119. Mechanistic dissection further disclosed that RYBP directly binds to ubiquitin protein ligase E3A (UBE3A) to promote its ubiquitination and proteasomal degradation in an autoubiquitination-independent manner. The resultant reduction of UBE3A protein level alleviates its effect on ubiquitination-mediated degradation of Ring1B, therefore resulting in increased stability and enhanced transcriptional repressor activity on its target genes. Thus, our current findings lay a foundation for understanding how RYBP functions in nc-PRC1 complexes, which is involved in development, stem cell maintenance, and carcinogenesis.-Li, M., Zhang, S., Zhao, W., Hou, C., Ma, X., Li, X., Huang, B., Chen, H., Chen, D. RYBP modulates stability and function of Ring1B through targeting UBE3A.

Fat mass and obesity-associated (FTO) protein regulates adult neurogenesis.

Fat mass and obesity-associated gene (FTO) is a member of the Fe (II)- and oxoglutarate-dependent AlkB dioxygenase family and is linked to both obesity and intellectual disability. The role of FTO in neurodevelopment and neurogenesis, however, remains largely unknown. Here we show that FTO is expressed in adult neural stem cells and neurons and displays dynamic expression during postnatal neurodevelopment. The loss of FTO leads to decreased brain size and body weight. We find that FTO deficiency could reduce the proliferation and neuronal differentiation of adult neural stem cells in vivo, which leads to impaired learning and memory. Given the role of FTO as a demethylase of N6-methyladenosine (m6A), we went on to perform genome-wide m6A profiling and observed dynamic m6A modification during postnatal neurodevelopment. The loss of FTO led to the altered expression of several key components of the brain derived neurotrophic factor pathway that were marked by m6A. These results together suggest FTO plays important roles in neurogenesis, as well as in learning and memory.

Development of an optical defect inspection algorithm based on an active contour model for large steel roller surfaces.

On-site measurements and defect detection are of great importance for precision ground steel rollers due to their large dimension and weight. In addition to dimensional error, form accuracy, surface roughness, and surface/sub-surface cracks, there also exist optical defect requirements for steel roller surfaces, e.g., speckles, chatter marks, or feed traces. Since rollers with optical defects will always duplicate the defect patterns onto the metal sheet or foil during rolling, it is necessary as well as significant to scrutinize the roller surface after grinding. In industrial practice, defects are investigated mainly by experienced engineers through naked-eye inspections along particular directions and under appropriate illumination conditions. This is usually subjective and inconsistent. In this paper, a machine vision system is developed, to add onto the roller grinder, that is capable of acquiring the roller's surface image with high and consistent quality. In addition, to identify defects with fuzzy boundaries, intensity inhomogeneity, and complex background textures, an improved segmentation algorithm is developed based on an active contour without edges model. Furthermore, qualitative and quantitative comparisons of the proposed algorithm with the Chan-Vese model, the local binary fitting model, and the globally signed region pressure force model are carried out. The comparisons prove that the proposed method performs with better accuracy and robustness for fuzzy and inhomogeneous defect segmentation and consumes generally less computational time.

Genome-wide alteration of 5-hydroxymenthylcytosine in a mouse model of Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) is the most common form of neurodegenerative disorder that leads to a decline in cognitive function. In AD, aggregates of amyloid ß peptide precede the accumulation of neurofibrillary tangles, both of which are hallmarks of the disease. The great majority (>90 %) of the AD cases are not originated from genetic defects, therefore supporting the central roles of epigenetic modifications that are acquired progressively during the life span. Strong evidences have indicated the implication of epigenetic modifications, including histone modification and DNA methylation, in AD. Recent studies revealed that 5-hydroxymethylcytosine (5hmC) is dynamically regulated during neurodevelopment and aging. RESULTS: We show that amyloid peptide 1-42 (Aß1-42) could significantly reduce the overall level of 5hmC in vitro. We found that the level of 5hmC displayed differential response to the pathogenesis in different brain regions, including the cortex, cerebellum, and hippocampus of APP-PSEN1 double transgenic (DTg) mice. We observed a significant decrease of overall 5hmC in hippocampus, but not in cortex and cerebellum, as the DTg mice aged. Genome-wide profiling identified differential hydroxymethylation regions (DhMRs) in DTg mice, which are highly enriched in introns, exons and intergenic regions. Gene ontology analyses indicated that DhMR-associated genes are highly enriched in multiple signaling pathways involving neuronal development/differentiation and neuronal function/survival. CONCLUSIONS: 5hmC-mediated epigenetic regulation could potentially be involved in the pathogenesis of AD.

Expanded GGGGCC repeat RNA associated with amyotrophic lateral sclerosis and frontotemporal dementia causes neurodegeneration.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) share phenotypic and pathologic overlap. Recently, an expansion of GGGGCC repeats in the first intron of C9orf72 was found to be a common cause of both illnesses; however, the molecular pathogenesis of this expanded repeat is unknown. Here we developed both Drosophila and mammalian models of this expanded hexanucleotide repeat and showed that expression of the expanded GGGGCC repeat RNA (rGGGGCC) is sufficient to cause neurodegeneration. We further identified Pur α as the RNA-binding protein of rGGGGCC repeats and discovered that Pur α and rGGGGCC repeats interact in vitro and in vivo in a sequence-specific fashion that is conserved between mammals and Drosophila. Furthermore, overexpression of Pur α in mouse neuronal cells and Drosophila mitigates rGGGGCC repeat-mediated neurodegeneration, and Pur α forms inclusions in the fly eye expressing expanded rGGGGCC repeats, as well as in cerebellum of human carriers of expanded GGGGCC repeats. These data suggest that expanded rGGGGCC repeats could sequester specific RNA-binding protein from their normal functions, ultimately leading to cell death. Taken together, these findings suggest that the expanded rGGGGCC repeats could cause neurodegeneration, and that Pur α may play a role in the pathogenesis of amyotrophic lateral sclerosis and frontotemporal dementia.