Understanding the underlying mechanisms of memory formation and maintenance has been a major goal in the field of neuroscience. Memory formation and maintenance are tightly controlled complex processes. Among the various processes occurring at different levels, gene expression regulation is especially crucial for proper memory processing, as some genes need to be activated while some genes must be suppressed. Epigenetic regulation of the genome involves processes such as DNA methylation and histone post-translational modifications. These processes edit genomic properties or the interactions between the genome and histone cores. They then induce structural changes in the chromatin and lead to transcriptional changes of different genes. Recent studies have focused on the concept of chromatin remodeling, which consists of 3D structural changes in chromatin in relation to gene regulation, and is an important process in learning and memory. In this review, we will introduce three major epigenetic processes involved in memory regulation: DNA methylation, histone methylation and histone acetylation. We will also discuss general mechanisms of long-term memory storage and relate the epigenetic control of learning and memory to chromatin remodeling. Finally, we will discuss how epigenetic mechanisms can contribute to the pathologies of neurological disorders and cause memory-related symptoms.
Acetylation ; Chromatin Assembly and Disassembly* ; Chromatin* ; DNA Methylation ; Epigenesis, Genetic ; Epigenomics* ; Gene Expression Regulation ; Genome ; Histones ; Learning* ; Memory* ; Memory, Long-Term ; Methylation ; Nervous System Diseases ; Neurosciences ; Pathology ; Protein Processing, Post-Translational

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). This study investigated the role of glucose-regulated protein 78 (GRP78) in EBI after SAH. Male Sprague-Dawley rats (n=108) weighing 260±40 g were divided into control, sham-operated, and operated groups. Blood was injected into the prechiasmatic cistern of rats in the operated group. Neurological scores, ultrastructures of neurons, apoptosis, and GRP78 expression in the hippocampus were examined using Garcia scoring system, transmission electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling, and Western blotting at 1, 6, 12, 24, 48, and 72 h after SAH, respectively. The results showed that neurological scores were significantly decreased in the operated group as compared with those in control and sham-operated groups at 12, 24, 48, and 72 h. Metachromatin, chromatin pyknosis at the edge, endoplasmic reticulum swelling, and invagination of nuclear membrane were observed at 24 h in the operated group, indicating the early morphological changes of apoptosis. The number of apoptotic cells was significantly increased in the operated group as compared with that in control and sham-operated groups at 6, 12, 24, 48, and 72 h. The GRP78 protein expression levels in the operated group were significantly elevated at all time points and reached the peak at 12 h. GRP78 expression was positively associated with apoptosis cells and negatively with neurological scores. In conclusion, EBI was demonstrated to occur after SAH and GRP78 was involved in the development of EBI after SAH.
Animals ; Apoptosis ; Brain Injuries ; complications ; metabolism ; pathology ; Chromatin ; pathology ; Endoplasmic Reticulum Stress ; Heat-Shock Proteins ; genetics ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Subarachnoid Hemorrhage ; etiology ; metabolism ; pathology

BACKGROUNDThe acute myeloid leukemia 1 (AML1)-eight-twenty-one (ETO) fusion protein generated by the t(8;21)(q22;q22) translocation is considered to display a crucial role in leukemogenesis in AML. By focusing on the anti-leukemia effects of eyes absent 4 (EYA4) gene on AML cells, we investigated the biologic and molecular mechanism associated with AML1-ETO expressed in t(8;21) AML.

METHODSQualitative polymerase chain reaction (PCR), quantitative reverse transcription PCR (RT-PCR), and Western blotting analysis were used to observe the mRNA and protein expression levels of EYA4 in cell lines. Different plasmids (including mutant plasmids) of dual luciferase reporter vector were built to study the binding status of AML1-ETO to the promoter region of EYA4. Chromatin immunoprecipitation assay was used to study the epigenetic silencing mechanism of EYA4. Bisulfite sequencing was applied to detect the methylation status in EYA4 promoter region. The influence of EYA4 gene in the cell proliferation, apoptosis, and cell clone-forming ability was detected by the technique of Cell Counting Kit-8, flow cytometry, and clonogenic assay.

RESULTSEYA4 gene was hypermethylated in AML1-ETO+ patients and its expression was down-regulated by 6-fold in Kasumi-1 and SKNO-1 cells, compared to HL-60 and SKNO-1-siA/E cells, respectively. We demonstrated that AML1-ETO triggered the epigenetic silencing of EYA4 gene by binding at AML1-binding sites and recruiting histone deacetylase 1 and DNA methyltransferases. Enhanced EYA4 expression levels inhibited cellular proliferation and suppressed cell colony formation in AML1-ETO+ cell lines. We also found EYA4 transfection increased apoptosis of Kasumi-1 and SKNO-1 cells by 1.6-fold and 1.4-fold compared to negative control, respectively.

CONCLUSIONSOur study identified EYA4 gene as targets for AML1-ETO and indicated it as a novel tumor suppressor gene. In addition, we provided evidence that EYA4 gene might be a novel therapeutic target and a potential candidate for treating AML1-ETO+ t (8;21) AML.

Apoptosis ; genetics ; physiology ; Blotting, Western ; Cell Line, Tumor ; Cell Proliferation ; genetics ; physiology ; Chromatin Immunoprecipitation ; Core Binding Factor Alpha 2 Subunit ; genetics ; metabolism ; DNA Methylation ; genetics ; Epigenesis, Genetic ; genetics ; Gene Silencing ; HL-60 Cells ; Humans ; Leukemia, Myeloid, Acute ; genetics ; metabolism ; pathology ; Oncogene Proteins, Fusion ; genetics ; metabolism ; RNA, Small Interfering ; genetics ; RUNX1 Translocation Partner 1 Protein ; Radioimmunoprecipitation Assay ; Trans-Activators ; genetics ; metabolism

During normal postnatal mammary gland development and adult remodeling related to the menstrual cycle, pregnancy, and lactation, ovarian hormones and peptide growth factors contribute to the delineation of a definite epithelial cell identity. This identity is maintained during cell replication in a heritable but DNA-independent manner. The preservation of cell identity is fundamental, especially when cells must undergo changes in response to intrinsic and extrinsic signals. The maintenance proteins, which are required for cell identity preservation, act epigenetically by regulating gene expression through DNA methylation, histone modification, and chromatin remodeling. Among the maintenance proteins, the Trithorax (TrxG) and Polycomb (PcG) group proteins are the best characterized. In this review, we summarize the structures and activities of the TrxG and PcG complexes and describe their pivotal roles in nuclear estrogen receptor activity. In addition, we provide evidence that perturbations in these epigenetic regulators are involved in disrupting epithelial cell identity, mammary gland remodeling, and breast cancer initiation.
Animals ; Breast Neoplasms ; genetics ; pathology ; physiopathology ; Cell Transformation, Neoplastic ; Chromatin ; genetics ; metabolism ; Epigenesis, Genetic ; physiology ; Epithelial Cells ; cytology ; Female ; Gene Expression Profiling ; Gene Expression Regulation, Developmental ; Histone-Lysine N-Methyltransferase ; Humans ; Mammary Glands, Animal ; cytology ; growth & development ; Mammary Glands, Human ; cytology ; growth & development ; Myeloid-Lymphoid Leukemia Protein ; genetics ; physiology ; Polycomb-Group Proteins ; genetics ; physiology ; Receptors, Estrogen ; metabolism

BACKGROUND AND OBJECTIVES: Auditory neuropathy is a hearing disorder characterized by the absence or the marked impairment of the auditory brainstem responses with the preservation of the cochlear microphonics (CMs) and otoacoustic emissions. This suggests that outer hair cell (OHC) function is normal but proximal auditory function to OHCs is impaired. It is assumed that the lesion is localized at the level of the inner hair cells (IHCs), auditory nerve fibers, or the synapse between them. This study was aimed to observe the change of hearing threshold and pathology of spiral ganglion cell induced by ouabain application, and present basic data to explain the auditory neuropathy. MATERIALS AND METHOD: Twenty ears of twenty normal hearing cats were used in this study. Cats were treated with 100 microL ouabain (1 mM) applied on the round window. After three days, compound action potential (CAP) and CM were measured and the cochlea was obtained. Pathologic change of spiral ganglion cell was evaluated under light microscope after H&E stain. Normal saline was injected for the control group. RESULTS: In the ouabain group, CAP threshold was increased in all tested frequencies (p<0.001) and the difference of CM threshold was not significant in all frequencies (p>0.05). There was significant difference between CAP and CM threshold shift (p<0.001). In the control group, there was no significant difference in CAP and CM thresholds. Light microscopic findings show that the condensed chromatin and nuclear fragments of spiral ganglion cells of an ear was exposed to ouabain, and outer hair cell and inner hair cell were not damaged. CONCLUSION: This study shows that the CAP threshold was significantly increased but the CM threshold was not changed in the ouabain group. Ouabain induced damage of spiral ganglion cells. This study is not sufficient to explain auditory neuropathy because threshold shift of CAP is not obvious, but it would be helpful to explain that selective damage of spiral ganglion cell would be the mechanism of auditory neuropathy.
Action Potentials ; Animals ; Cats* ; Chromatin ; Cochlea ; Cochlear Nerve ; Ear ; Evoked Potentials, Auditory, Brain Stem ; Hair ; Hearing ; Hearing Disorders ; Ouabain* ; Pathology ; Spiral Ganglion* ; Synapses

Epigenetic alterations are associated with all aspects of cancer, from tumor initiation to cancer progression and metastasis. It is now well understood that both losses and gains of DNA methylation as well as altered chromatin organization contribute significantly to cancer-associated phenotypes. More recently, new sequencing technologies have allowed the identification of driver mutations in epigenetic regulators, providing a mechanistic link between the cancer epigenome and genetic alterations. Oncogenic activating mutations are now known to occur in a number of epigenetic modifiers (i.e. IDH1/2, EZH2, DNMT3A), pinpointing epigenetic pathways that are involved in tumorigenesis. Similarly, investigations into the role of inactivating mutations in chromatin modifiers (i.e. KDM6A, CREBBP/EP300, SMARCB1) implicate many of these genes as tumor suppressors. Intriguingly, a number of neoplasms are defined by a plethora of mutations in epigenetic regulators, including renal, bladder, and adenoid cystic carcinomas. Particularly striking is the discovery of frequent histone H3.3 mutations in pediatric glioma, a particularly aggressive neoplasm that has long remained poorly understood. Cancer epigenetics is a relatively new, promising frontier with much potential for improving cancer outcomes. Already, therapies such as 5-azacytidine and decitabine have proven that targeting epigenetic alterations in cancer can lead to tangible benefits. Understanding how genetic alterations give rise to the cancer epigenome will offer new possibilities for developing better prognostic and therapeutic strategies.
Chromatin ; metabolism ; Chromatin Assembly and Disassembly ; DNA Methylation ; Enhancer of Zeste Homolog 2 Protein ; Epigenesis, Genetic ; Histones ; metabolism ; Humans ; Neoplasms ; genetics ; metabolism ; pathology ; Polycomb Repressive Complex 2 ; genetics ; metabolism

OBJECTIVETo evaluate the sperm DNA fragmentation index (DFI) and sperm malformation rate (SMR) before intracytoplasmic sperm injection (ICSI) and their impact on the clinical outcome of ICSI.

METHODSThis study included 79 cycles of ICSI because of oligoasthenozoospermia. We detected the sperm concentration, percentage of progressively motile sperm, DFI and SMR at 3 to 6 months before ICSI, and analyzed the relationship of DFI and SMR with the outcome parameters.

RESULTSOf the 79 oligoasthenozoospermia cases, DFI was found to be normal (< or = 25%) in 51 and abnormal (> 25%) in the other 28, significantly increased in the latter (14.18% vs 41.47%), and coincidently, SMR, too, was normal (< or = 96%) in 51 cases and abnormal (> 96%) in 28, significantly higher in the abnormal than in the normal cases (87.88% vs 98.46%). There were no significant differences between the normal and abnormal DFI groups in age, females'BMI, number of oocytes retrieved, and number of embryos transferred, nor between the normal and abnormal SMR groups in the number of fertilized oocytes and quality embryos, biochemical pregnancy, clinical pregnancy, and early pregnancy loss. Sperm DFI was significantly positively correlated with SMR (r = 0.231, P < 0.05).

CONCLUSIONICSI may reduce the rates of biochemical pregnancy and clinical pregnancy for men with increased sperm DFI (> 25%) and SMR (> 96%) by strict detection criteria, but with no statistically significant difference from normal males. Our findings need to be supported by further studies with larger sample sizes.

Adult ; Chromatin ; DNA Fragmentation ; Female ; Humans ; Male ; Middle Aged ; Pregnancy ; Pregnancy Rate ; Sperm Injections, Intracytoplasmic ; Spermatozoa ; pathology ; Treatment Outcome ; Young Adult

OBJECTIVETo investigate sperm DNA integrity in male infertility patients with hepatitis B virus (HBV) infection.

METHODSThis study included 90 infertile men with HBV infection (group A), 82 infertile men without HBV infection (group B) and 70 normal fertile men (group C). We detected sperm DNA integrity among the subjects, including DNA fragmentation index (DFI) and high DNA stainability (HDS), by sperm chromatin structure assay (SCSA), and compared them among the three groups.

RESULTSDFI was higher in group A ([28.17 +/- 13.06]%) than in B ([26.64 +/- 9.79]%) and C ([15.67 +/- 4.73]%), significantly higher in A and B than in C (P < 0.05) but with no significant difference between A and B (P > 0.05). HDS was higher in group A ([10.83 +/- 5.601]%) than in B ([9.04 +/- 3.48]%) and C ([8.04-2.25]%), with significant difference between A and C (P < 0.05).

CONCLUSIONSperm DNA integrity of infertile males is significantly different from that of normal fertile men, and infertility with HBV infection further impairs sperm DNA, which is manifested by abnormal sperm nuclear maturity.

Adult ; Case-Control Studies ; Chromatin ; DNA ; genetics ; DNA Damage ; Hepatitis B ; pathology ; Hepatitis B virus ; Humans ; Infertility, Male ; genetics ; virology ; Male ; Sperm Count ; Spermatozoa ; pathology ; Young Adult

Hannum and colleagues performed DNA methylation sequencing to examine the relationship between DNA methylome and aging rate. Notably, they succeeded in building a quantitative and reproducible model based on the epigenetic bio-markers to predict aging rate with high accuracy. This progress enlightens us in many aspects particularly in applying this novel set of bio-markers on studying the mechanism of aging rate using adult tissue-specific stem cells, building up a potential quantitative model to explore the mechanism for other epigenetic factors like non-coding RNA, and understanding the principle and mechanism of 3D chromatin structure in epigenetic modulation.
Aging ; genetics ; pathology ; Base Sequence ; Chromatin ; genetics ; DNA Methylation ; genetics ; Epigenesis, Genetic ; Genome, Human ; Humans ; RNA, Untranslated ; genetics ; Sequence Analysis, DNA ; trends

Chromatin ; genetics ; metabolism ; Epigenesis, Genetic ; Genomic Instability ; Histones ; metabolism ; Humans ; Neoplasms ; metabolism ; pathology ; Ubiquitin-Protein Ligases ; genetics ; metabolism