Fe65 is required for Tip60-directed histone H4 acetylation at DNA strand breaks

Evidence that Alzheimer's Disease Is a Disease of Competitive Synaptic Plasticity Gone Awry

 Mounting evidence indicates that a physiological function of amyloid-β (Aβ) is to mediate neural activity-dependent homeostatic and competitive synaptic plasticity in the brain. I have previously summarized the lines of evidence supporting this hypothesis and highlighted the similarities between Aβ and anti-microbial peptides in mediating cell/synapse competition. In cell competition, anti-microbial peptides deploy a multitude of mechanisms to ensure both self-protection and competitor elimination. Here I review recent studies showing that similar mechanisms are at play in Aβ-mediated synapse competition and perturbations in these mechanisms underpin Alzheimer's disease (AD). Specifically, I discuss evidence that Aβ and ApoE, two crucial players in AD, co-operate in the regulation of synapse competition. Glial ApoE promotes self-protection by increasing the production of trophic monomeric Aβ and inhibiting its assembly into toxic oligomers. Conversely, Aβ oligomers, once assembled, promote the elimination of competitor synapses via direct toxic activity and amplification of "eat-me" signals promoting the elimination of weak synapses. I further summarize evidence that neuronal ApoE may be part of a gene regulatory network that normally promotes competitive plasticity, explaining the selective vulnerability of ApoE expressing neurons in AD brains. Lastly, I discuss evidence that sleep may be key to Aβ-orchestrated plasticity, in which sleep is not only induced by Aβ but is also required for Aβ-mediated plasticity, underlining the link between sleep and AD. Together, these results strongly argue that AD is a disease of competitive synaptic plasticity gone awry, a novel perspective that may promote AD research.

Alpha-secretase dependent nuclear localization of the amyloid-β precursor protein-binding protein Fe65 promotes DNA repair

Fe65 is a brain enriched adaptor protein involved in various cellular processes, including actin cytoskeleton regulation, DNA repair and transcription. A well-studied interacting partner of Fe65 is the transmembrane amyloid-β precursor protein (APP), which can undergo regulated intramembrane proteolysis (RIP). Following β- and γ-secretase-mediated RIP, the released APP intracellular domain (AICD) together with Fe65 can translocate to the nucleus and regulate transcription. In this study, we investigated if Fe65 nuclear localization can also be regulated by different α-secretases, also known to participate in RIP of APP and other transmembrane proteins. We found that in both Phorbol 12-myristate 13-acetate and all-trans retinoic acid differentiated neuroblastoma cells a strong negative impact on Fe65 nuclear localization, equal to the effect observed upon γ-secretase inhibition, could be detected following inhibition of all three (ADAM9, ADAM10 and ADAM17) α-secretases. Moreover, using the comet assay and analysis of Fe65 dependent DNA repair associated posttranslational modifications of histones, we could show that inhibition of α-secretase-mediated Fe65 nuclear translocation resulted in impaired capacity of the cells to repair DNA damage. Taken together this suggests that α-secretase processing of APP and/or other Fe65 interacting transmembrane proteins play an important role in regulating Fe65 nuclear translocation and DNA repair.

Dynamic SUMOylation of MORC2 orchestrates chromatin remodelling and DNA repair in response to DNA damage and drives chemoresistance in breast cancer

Rationale: SUMOylation regulates a plethora of biological processes, and its inhibitors are currently under investigation in clinical trials as anticancer agents. Thus, identifying new targets with site-specific SUMOylation and defining their biological functions will not only provide new mechanistic insights into the SUMOylation signaling but also open an avenue for developing new strategy for cancer therapy. MORC family CW-type zinc finger 2 (MORC2) is a newly identified chromatin-remodeling enzyme with an emerging role in the DNA damage response (DDR), but its regulatory mechanism remains enigmatic. Methods: In vivo and in vitro SUMOylation assays were used to determine the SUMOylation levels of MORC2. Overexpression and knockdown of SUMO-associated enzymes were used to detect their effects on MORC2 SUMOylation. The effect of dynamic MORC2 SUMOylation on the sensitivity of breast cancer cells to chemotherapeutic drugs was examined through in vitro and in vivo functional assays. Immunoprecipitation, GST pull-down, MNase, and chromatin segregation assays were used to explore the underlying mechanisms. Results: Here, we report that MORC2 is modified by small ubiquitin-like modifier 1 (SUMO1) and SUMO2/3 at lysine 767 (K767) in a SUMO-interacting motif dependent manner. MORC2 SUMOylation is induced by SUMO E3 ligase tripartite motif containing 28 (TRIM28) and reversed by deSUMOylase sentrin-specific protease 1 (SENP1). Intriguingly, SUMOylation of MORC2 is decreased at the early stage of DNA damage induced by chemotherapeutic drugs that attenuate the interaction of MORC2 with TRIM28. MORC2 deSUMOylation induces transient chromatin relaxation to enable efficient DNA repair. At the relatively late stage of DNA damage, MORC2 SUMOylation is restored, and SUMOylated MORC2 interacts with protein kinase CSK21 (casein kinase II subunit alpha), which in turn phosphorylates DNA-PKcs (DNA-dependent protein kinase catalytic subunit), thus promoting DNA repair. Notably, expression of a SUMOylation-deficient mutant MORC2 or administration of SUMO inhibitor enhances the sensitivity of breast cancer cells to DNA-damaging chemotherapeutic drugs. Conclusions: Collectively, these findings uncover a novel regulatory mechanism of MORC2 by SUMOylation and reveal the intricate dynamics of MORC2 SUMOylation important for proper DDR. We also propose a promising strategy to sensitize MORC2-driven breast tumors to chemotherapeutic drugs by inhibition of the SUMO pathway.

Identification of epigenetic modifications mediating the antagonistic effect of selenium against cadmium-induced breast carcinogenesis

The antagonistic effect of selenium (Se) against cadmium (Cd)-induced breast carcinogenesis was reported, but underlying mechanisms were unclear. The aim of this study was to identify the epigenetically regulated genes and biological pathways mediating the antagonistic effect. We exposed MCF-7 cells to Cd and Se alone or simultaneously. Cell proliferation was assessed by MTT assay, and differential epigenome (DNA methylation, microRNA, and long non-coding RNA) was obtained by microarrays. We cross-verified the epigenetic markers with differential transcriptome, and the ones modulated by Cd and Se in opposite directions were regarded to mediate the antagonistic effect. The epigenetically regulated genes were validated by using gene expression data in human breast tissues. We further assessed the biological functions of these validated genes. Our results showed that Se alleviated the proliferative effect of Cd on MCF-7 cell. A total of 10 epigenetically regulated genes were regarded to mediate the antagonistic effect, including APBA2, KIAA0895, DHX35, CPEB3, SVIL, MYLK, ZFYVE28, ABLIM2, GRB10, and PCDH9. Biological function analyses suggested that these epigenetically regulated genes were involved in multiple cancer-related pathways, such as focal adhesion and PI3K/Akt pathway. In conclusion, we provided evidence that Se antagonized the Cd-induced breast carcinogenesis via epigenetic modification and revealed the critical pathways.

Preferential Involvement of BRCA1/BARD1, Not Tip60/Fe65, in DNA Double-Strand Break Repair in Presenilin-1 P117L Alzheimer Models

Recently, we showed that DNA double-strand breaks (DSBs) are increased by the Aβ₄₂-amyloid peptide and decreased by all-trans retinoic acid (RA) in SH-SY5Y cells and C57BL/6J mice. The present work was aimed at investigating DSBs in cells and murine models of Alzheimer's disease carrying the preseniline-1 (PS1) P117L mutation. We observed that DSBs could hardly decrease following RA treatment in the mutated cells compared to the wild-type cells. The activation of the amyloidogenic pathway is proposed in the former case as Aβ₄₂- and RA-dependent DSBs changes were reproduced by an α-secretase and a γ-secretase inhibitions, respectively. Unexpectedly, the PS1 P117L cells showed lower DSB levels than the controls. As the DSB repair proteins Tip60 and Fe65 were less expressed in the mutated cell nuclei, they do not appear to contribute to this difference. On the contrary, full-length BRCA1 and BARD1 proteins were significantly increased in the chromatin compartment of the mutated cells, suggesting that they decrease DSBs in the pathological situation. These Western blot data were corroborated by in situ proximity ligation assays: the numbers of BRCA1-BARD1, not of Fe65-Tip60 heterodimers, were increased only in the mutated cell nuclei. RA also enhanced the expression of BARD1 and of the 90 kDa BRCA1 isoform. The increased BRCA1 expression in the mutated cells can be related to the enhanced difficulty to inhibit this pathway by BRCA1 siRNA in these cells. Overall, our study suggests that at earlier stages of the disease, similarly to PS1 P117L cells, a compensatory mechanism exists that decreases DSB levels via an activation of the BRCA1/BARD1 pathway. This supports the importance of this pathway in neuroprotection against Alzheimer's disease.

RBM6 splicing factor promotes homologous recombination repair of double-strand breaks and modulates sensitivity to chemotherapeutic drugs

RNA-binding proteins regulate mRNA processing and translation and are often aberrantly expressed in cancer. The RNA-binding motif protein 6, RBM6, is a known alternative splicing factor that harbors tumor suppressor activity and is frequently mutated in human cancer. Here, we identify RBM6 as a novel regulator of homologous recombination (HR) repair of DNA double-strand breaks (DSBs). Mechanistically, we show that RBM6 regulates alternative splicing-coupled nonstop-decay of a positive HR regulator, Fe65/APBB1. RBM6 knockdown leads to a severe reduction in Fe65 protein levels and consequently impairs HR of DSBs. Accordingly, RBM6-deficient cancer cells are vulnerable to ATM and PARP inhibition and show remarkable sensitivity to cisplatin. Concordantly, cisplatin administration inhibits the growth of breast tumor devoid of RBM6 in mouse xenograft model. Furthermore, we observe that RBM6 protein is significantly lost in metastatic breast tumors compared with primary tumors, thus suggesting RBM6 as a potential therapeutic target of advanced breast cancer. Collectively, our results elucidate the link between the multifaceted roles of RBM6 in regulating alternative splicing and HR of DSBs that may contribute to tumorigenesis, and pave the way for new avenues of therapy for RBM6-deficient tumors.

Genome instability and loss of protein homeostasis: converging paths to neurodegeneration?

Genome instability and loss of protein homeostasis are hallmark events of age-related diseases that include neurodegeneration. Several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis are characterized by protein aggregation, while an impaired DNA damage response (DDR) as in many genetic DNA repair disorders leads to pronounced neuropathological features. It remains unclear to what degree these cellular events interconnect with each other in the development of neurological diseases. This review highlights how the loss of protein homeostasis and genome instability influence one other. We will discuss studies that illustrate this connection. DNA damage contributes to many neurodegenerative diseases, as shown by an increased level of DNA damage in patients, possibly due to the effects of protein aggregates on chromatin, the sequestration of DNA repair proteins and novel putative DNA repair functions. Conversely, genome stability is also important for protein homeostasis. For example, gene copy number variations and the loss of key DDR components can lead to marked proteotoxic stress. An improved understanding of how protein homeostasis and genome stability are mechanistically connected is needed and promises to lead to the development of novel therapeutic interventions.

TIP60 in aging and neurodegeneration

Epigenetic modification of chromatin, including histone methylation and acetylation, plays critical roles in eukaryotic cells and has a significant impact on chromatin structure/accessibility, gene regulation and, susceptibility to aging, neurodegenerative disease, cancer, and other age-related diseases. This article reviews the current advances on TIP60/KAT5, a major histone acetyltransferase with diverse functions in eukaryotes, with emphasis on its regulation of autophagy, proteasome-dependent protein turnover, RNA transcription, DNA repair, circadian rhythms, learning and memory, and other neurological functions implicated in aging and neurodegeneration. Moreover, the promising therapeutic potential of TIP60 is discussed to target Alzheimer's disease and other neurological diseases.

The Role of Posttranslational Modifications in DNA Repair

The human body is a complex structure of cells, which are exposed to many types of stress. Cells must utilize various mechanisms to protect their DNA from damage caused by metabolic and external sources to maintain genomic integrity and homeostasis and to prevent the development of cancer. DNA damage inevitably occurs regardless of physiological or abnormal conditions. In response to DNA damage, signaling pathways are activated to repair the damaged DNA or to induce cell apoptosis. During the process, posttranslational modifications (PTMs) can be used to modulate enzymatic activities and regulate protein stability, protein localization, and protein-protein interactions. Thus, PTMs in DNA repair should be studied. In this review, we will focus on the current understanding of the phosphorylation, poly(ADP-ribosyl)ation, ubiquitination, SUMOylation, acetylation, and methylation of six typical PTMs and summarize PTMs of the key proteins in DNA repair, providing important insight into the role of PTMs in the maintenance of genome stability and contributing to reveal new and selective therapeutic approaches to target cancers.

VRK1 Phosphorylates Tip60/KAT5 and Is Required for H4K16 Acetylation in Response to DNA Damage

Dynamic remodeling of chromatin requires acetylation and methylation of histones, frequently affecting the same lysine residue. These alternative epigenetic modifications require the coordination of enzymes, writers and erasers, mediating them such as acetylases and deacetylases. In cells in G0/G1, DNA damage induced by doxorubicin causes an increase in histone H4K16ac, a marker of chromatin relaxation. In this context, we studied the role that VRK1, a chromatin kinase activated by DNA damage, plays in this early step. VRK1 depletion or MG149, a Tip60/KAT5 inhibitor, cause a loss of H4K16ac. DNA damage induces the phosphorylation of Tip60 mediated by VRK1 in the chromatin fraction. VRK1 directly interacts with and phosphorylates Tip60. Furthermore, the phosphorylation of Tip60 induced by doxorubicin is lost by depletion of VRK1 in both ATM +/+ and ATM-/- cells. Kinase-active VRK1, but not kinase-dead VRK1, rescues Tip60 phosphorylation induced by DNA damage independently of ATM. The Tip60 phosphorylation by VRK1 is necessary for the activating acetylation of ATM, and subsequent ATM autophosphorylation, and both are lost by VRK1 depletion. These results support that the VRK1 chromatin kinase is an upstream regulator of the initial acetylation of histones, and an early step in DNA damage responses (DDR).

Epigenetic Mechanisms of Learning and Memory: Implications for Aging

The neuronal epigenome is highly sensitive to external events and its function is vital for producing stable behavioral outcomes, such as the formation of long-lasting memories. The importance of epigenetic regulation in memory is now well established and growing evidence points to altered epigenome function in the aging brain as a contributing factor to age-related memory decline. In this review, we first summarize the typical role of epigenetic factors in memory processing in a healthy young brain, then discuss the aspects of this system that are altered with aging. There is general agreement that many epigenetic marks are modified with aging, but there are still substantial inconsistencies in the precise nature of these changes and their link with memory decline. Here, we discuss the potential source of age-related changes in the epigenome and their implications for therapeutic intervention in age-related cognitive decline.

Garcinol, a multifaceted sword for the treatment of Parkinson's disease

Garcinol, the principal phytoconstituent of plants belonging to the genus Garcinia, is known for its anti-oxidant as well as anti-inflammatory properties, which can be extended to its possible neuroprotective role. Recent reports disseminate the capacity of garcinol to influence neuronal growth and survival, alter the neurochemical status in brain, as well as regulate memory and cognition. The concomitant neuro-rescue property of garcinol may render it as an effective compound in Parkinson's disease (PD) therapeutics since it is capable of ameliorating the related pathophysiological changes. Emerging pieces of evidence linking histone acetylation defects to the progression of neurodegenerative diseases provide an effective basis for targeting PD. Hyperacetylation of histones has been reported in Parkinsonian brain, which demands the use of pharmacological inhibitors of histone acetyltransferases (HAT). Garcinol serves as a potent natural HAT inhibitor and has unveiled promising results in molecular interaction studies against Monoamine oxidase B (MAO-B) and Catechol-O-Methyltransferase (COMT), as well as in L-DOPA induced dyskinesia. This review highlights the prospective implications of garcinol as a novel anti-Parkinsonian agent, and establishes a bridge between histone acetylation defects and the pathological aspects of PD.

Complexity and Selectivity of γ-Secretase Cleavage on Multiple Substrates: Consequences in Alzheimer's Disease and Cancer

The processing of the amyloid-β protein precursor (AβPP) by β- and γ-secretases is a pivotal event in the genesis of Alzheimer's disease (AD). Besides familial mutations on the AβPP gene, or upon its overexpression, familial forms of AD are often caused by mutations or deletions in presenilin 1 (PSEN1) and 2 (PSEN2) genes: the catalytic components of the proteolytic enzyme γ-secretase (GS). The "amyloid hypothesis", modified over time, states that the aberrant processing of AβPP by GS induces the formation of specific neurotoxic soluble amyloid-β (Aβ) peptides which, in turn, cause neurodegeneration. This theory, however, has recently evidenced significant limitations and, in particular, the following issues are debated: 1) the concept and significance of presenilin's "gain of function" versus "loss of function"; and 2) the presence of several and various GS substrates, which interact with AβPP and may influence Aβ formation. The latter consideration is suggestive: despite the increasing number of GS substrates so far identified, their reciprocal interaction with AβPP itself, even in the AD field, is significantly unexplored. On the other hand, GS is also an important pharmacological target in the cancer field; inhibitors or GS activity are investigated in clinical trials for treating different tumors. Furthermore, the function of AβPP and PSENs in brain development and in neuronal migration is well known. In this review, we focused on a specific subset of GS substrates that directly interact with AβPP and are involved in its proteolysis and signaling, by evaluating their role in neurodegeneration and in cell motility or proliferation, as a possible connection between AD and cancer.

Convergent origination of a Drosophila-like dosage compensation mechanism in a reptile lineage

Sex chromosomes differentiated from different ancestral autosomes in various vertebrate lineages. Here, we trace the functional evolution of the XY Chromosomes of the green anole lizard (Anolis carolinensis), on the basis of extensive high-throughput genome, transcriptome and histone modification sequencing data and revisit dosage compensation evolution in representative mammals and birds with substantial new expression data. Our analyses show that Anolis sex chromosomes represent an ancient XY system that originated at least ≈160 million years ago in the ancestor of Iguania lizards, shortly after the separation from the snake lineage. The age of this system approximately coincides with the ages of the avian and two mammalian sex chromosomes systems. To compensate for the almost complete Y Chromosome degeneration, X-linked genes have become twofold up-regulated, restoring ancestral expression levels. The highly efficient dosage compensation mechanism of Anolis represents the only vertebrate case identified so far to fully support Ohno's original dosage compensation hypothesis. Further analyses reveal that X up-regulation occurs only in males and is mediated by a male-specific chromatin machinery that leads to global hyperacetylation of histone H4 at lysine 16 specifically on the X Chromosome. The green anole dosage compensation mechanism is highly reminiscent of that of the fruit fly, Drosophila melanogaster. Altogether, our work unveils the convergent emergence of a Drosophila-like dosage compensation mechanism in an ancient reptilian sex chromosome system and highlights that the evolutionary pressures imposed by sex chromosome dosage reductions in different amniotes were resolved in fundamentally different ways.

Fibrillar Amyloid-β Accumulation Triggers an Inflammatory Mechanism Leading to Hyperphosphorylation of the Carboxyl-Terminal End of Tau Polypeptide in the Hippocampal Formation of the 3×Tg-AD Transgenic Mouse

Alzheimer's disease (AD) is a degenerative and irreversible disorder whose progressiveness is dependent on age. It is histopathologically characterized by the massive accumulation of insoluble forms of tau and amyloid-β (Aβ) asneurofibrillary tangles and neuritic plaques, respectively. Many studies have documented that these two polypeptides suffer several posttranslational modifications employing postmortem tissue sections from brains of patients with AD. In order to elucidate the molecular mechanisms underlying the posttranslational modifications of key players in this disease, including Aβ and tau, several transgenic mouse models have been developed. One of these models is the 3×Tg-AD transgenic mouse, carrying three transgenes encoding APPSWE, S1M146V, and TauP301L proteins. To further characterize this transgenicmouse, we determined the accumulation of fibrillar Aβ as a function of age in relation to the hyperphosphorylation patterns of TauP301L at both its N- and C-terminus in the hippocampal formation by immunofluorescence and confocal microscopy. Moreover, we searched for the expression of activated protein kinases and mediators of inflammation by western blot of wholeprotein extracts from hippocampal tissue sections since 3 to 28 months as well. Our results indicate that the presence of fibrillar Aβ deposits correlates with a significant activation of astrocytes and microglia in subiculum and CA1 regions of hippocampus. Accordingly, we also observed a significant increase in the expression of TNF-α associated to neuritic plaques and glial cells. Importantly, there is an overexpression of the stress activated protein kinases SAPK/JNK and Cdk-5 in pyramidal neurons, which might phosphorylate several residues at the C-terminus of TauP301L. Therefore, the accumulation of Aβ oligomers results in an inflammatory environment that upregulates kinases involved in hyperphosphorylation of TauP301L polypeptide.

Extensive nuclear sphere generation in the human Alzheimer's brain

Nuclear spheres are protein aggregates consisting of FE65, TIP60, BLM, and other yet unknown proteins. Generation of these structures in the cellular nucleus is putatively modulated by the amyloid precursor protein (APP), either by its cleavage or its phosphorylation. Nuclear spheres were preferentially studied in cell culture models and their existence in the human brain had not been known. Existence of nuclear spheres in the human brain was studied using immunohistochemistry. Cell culture experiments were used to study regulative mechanisms of nuclear sphere generation. The comparison of human frontal cortex brain samples from Alzheimer's disease (AD) patients to age-matched controls revealed a dramatically and highly significant enrichment of nuclear spheres in the AD brain. Costaining demonstrated that neurons are distinctly affected by nuclear spheres, but astrocytes never are. Nuclear spheres were predominantly found in neurons that were negative for threonine 668 residue in APP phosphorylation. Cell culture experiments revealed that JNK3-mediated APP phosphorylation reduces the amount of sphere-positive cells. The study suggests that nuclear spheres are a new APP-derived central hallmark of AD, which might be of crucial relevance for the molecular mechanisms in neurodegeneration.

Fe65 Is Phosphorylated on Ser289 after UV-Induced DNA Damage

Fe65 undergoes a phosphatase-sensitive gel mobility shift after DNA damage, consistent with protein phosphorylation. A recent study identified Ser²²⁸ as a specific site of phosphorylation, targeted by the ATM and ATR protein kinases, with phosphorylation inhibiting the Fe65-dependent transcriptional activity of the amyloid precursor protein (APP). The direct binding of Fe65 to APP not only regulates target gene expression, but also contributes to secretase-mediated processing of APP, producing cytoactive proteolytic fragments including the APP intracellular domain (AICD) and cytotoxic amyloid β (Aβ) peptides. Given that the accumulation of Aβ peptides in neural plaques is a pathological feature of Alzheimer’s disease (AD), it is essential to understand the mechanisms controlling Aβ production. This will aid in the development of potential therapeutic agents that act to limit the deleterious production of Aβ peptides. The Fe65-APP complex has transcriptional activity and the complex is regulated by multiple post-translational modifications and other protein binding partners. In the present study, we have identified Ser²⁸⁹ as a novel site of UV-induced phosphorylation. Interestingly, this phosphorylation was mediated by ATM, rather than ATR, and occurred independently of APP. Neither phosphorylation nor mutation of Ser²⁸⁹ affected the Fe65-APP interaction, though this was markedly decreased after UV treatment, with a concomitant decrease in the protein levels of APP in cells. Using mutagenesis, we demonstrated that Fe65 Ser²⁸⁹ phosphorylation did not affect the transcriptional activity of the Fe65-APP complex, in contrast to the previously described Ser²²⁸ site.

Epigenetic Modifications in Neurological Diseases: Natural Products as Epigenetic Modulators a Treatment Strategy

Epigenetic modifications, including DNA methylation, covalent histone modifications, and small noncoding RNAs, play a key role in regulating the gene expression. This regulatory mechanism is important in cellular differentiation and development. Recent advances in the field of epigenetics extended the role of epigenetic mechanisms in controlling key biological processes such as genome imprinting and X-chromosome inactivation. Aberrant epigenetic modifications are associated with the development of many diseases. The role of epigenetic modifications in various neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, Huntington disease, epilepsy, and multiple sclerosis is rapidly emerging. The use of epigenetic modifying drugs to treat these diseases has been the interest in recent years. A number of natural products having diverse mechanism of action are used for drug discovery. For many years, natural compounds have been used to treat various neurodegenerative diseases, but the use of such compounds as epigenetic modulators to reverse or treat neurological diseases are not well studied. In this chapter, we mainly focus on how various epigenetic modifications play a key role in neurodegenerative diseases, their mechanism of action, and how it acts as a potential therapeutic target for epigenetic drugs to treat these diseases will be discussed.

Proteome-wide characterization of signalling interactions in the hippocampal CA4/DG subfield of patients with Alzheimer's disease

Alzheimer’s disease (AD) is the most common form of dementia; however, mechanisms and biomarkers remain unclear. Here, we examined hippocampal CA4 and dentate gyrus subfields, which are less studied in the context of AD pathology, in post-mortem AD and control tissue to identify possible biomarkers. We performed mass spectrometry-based proteomic analysis combined with label-free quantification for identification of differentially expressed proteins. We identified 4,328 proteins, of which 113 showed more than 2-fold higher or lower expression in AD hippocampi than in control tissues. Five proteins were identified as putative AD biomarkers (MDH2, PCLO, TRRAP, YWHAZ, and MUC19 isoform 5) and were cross-validated by immunoblotting, selected reaction monitoring, and MALDI imaging. We also used a bioinformatics approach to examine upstream signalling interactions of the 113 regulated proteins. Five upstream signalling (IGF1, BDNF, ZAP70, MYC, and cyclosporin A) factors showed novel interactions in AD hippocampi. Taken together, these results demonstrate a novel platform that may provide new strategies for the early detection of AD and thus its diagnosis.

Fe65 Ser228 is phosphorylated by ATM/ATR and inhibits Fe65-APP-mediated gene transcription

Fe65 binds the amyloid precursor protein (APP) and regulates the secretase-mediated processing of APP into several proteolytic fragments, including amyloid β-peptides (Aβ) and APP intracellular domain (AICD). Aβ accumulation in neural plaques is a pathological feature of Alzheimer's disease (AD) and AICD has important roles in the regulation of gene transcription (in complex with Fe65). It is therefore important to understand how Fe65 is regulated and how this contributes to the function and/or processing of APP. Studies have also implicated Fe65 in the cellular DNA damage response with knockout mice showing increased DNA strand breaks and Fe65 demonstrating a gel mobility shift after DNA damage, consistent with protein phosphorylation. In the present study, we identified Fe65 Ser(228) as a novel target of the ATM (ataxia telangiectasia mutated) and ATR (ataxia-telangiectasia- and Rad3-related protein) protein kinases, in a reaction that occurred independently of APP. Neither phosphorylation nor mutation of Ser(228) affected the Fe65-APP complex, though this was markedly decreased after UV treatment, with a concomitant decrease in the protein levels of APP in cells. Finally, mutation of Ser(228) to alanine (thus blocking phosphorylation) caused a significant increase in Fe65-APP transcriptional activity, whereas phosphomimetic mutants (S(228)D and S(228)E) showed decreased transcriptional activity. These studies identify a novel phosphorylation site within Fe65 and a novel regulatory mechanism for the transcriptional activity of the Fe65-APP complex.

A highly conserved program of neuronal microexons is misregulated in autistic brains

Alternative splicing (AS) generates vast transcriptomic and proteomic complexity. However, which of the myriad of detected AS events provide important biological functions is not well understood. Here, we define the largest program of functionally coordinated, neural-regulated AS described to date in mammals. Relative to all other types of AS within this program, 3-15 nucleotide "microexons" display the most striking evolutionary conservation and switch-like regulation. These microexons modulate the function of interaction domains of proteins involved in neurogenesis. Most neural microexons are regulated by the neuronal-specific splicing factor nSR100/SRRM4, through its binding to adjacent intronic enhancer motifs. Neural microexons are frequently misregulated in the brains of individuals with autism spectrum disorder, and this misregulation is associated with reduced levels of nSR100. The results thus reveal a highly conserved program of dynamic microexon regulation associated with the remodeling of protein-interaction networks during neurogenesis, the misregulation of which is linked to autism.

An epigenomic role of Fe65 in the cellular response to DNA damage

Previous findings describe Fe65 as a key protein in the cellular response to genotoxic stress. However, the precise molecular mechanism by which Fe65 contributes to DNA damage signaling remains unclear. In this study, we hypothesized that the transcriptional activity of Fe65 may contribute to DNA damage pathways by regulating gene expression patterns activated in response to genotoxic stress. To address this hypothesis, we mapped the global binding profile of Fe65 by chromatin immunoprecipitation (ChIP)-sequencing in the SK-N-SH cells exposed to genotoxic stress. Unexpectedly, the genome-wide location analysis showed a substantial enrichment of Fe65 in the promoter regions of coding genes linked to DNA damage signaling pathways. To further investigate the role of Fe65 in the transcriptional regulation of putative coding target genes identified by ChIP-seq, we performed microarray assays using wild-type (WT) or Fe65 deficient mouse embryonic fibroblasts (MEFs) exposed to oxidative stress with multiple recovery times. Gene ontology analysis of the Fe65-depedent transcriptome suggested that Fe65 modulates the expression of genes critical for DNA damage response. Motif enrichment analysis of regulatory regions occupied by Fe65 revealed a strong correlation with key transcription factors involved in DNA damage signaling pathways, including E2F1, p53, and Jun. Comparison of ChIP-sequencing results with microarray results ultimately identified 248 Fe65-depedent target genes, the majority of which were known regulators of cell cycle, cell death, and DNA replication and repair pathways. We validated the target genes identified by in silico analysis by qPCR experiments. Collectively, our results provide strong evidence that Fe65 plays a role in DNA damage response and cell viability by epigenomic regulation of specific transcriptional programs activated upon genotoxic stress.

A novel function of the Fe65 neuronal adaptor in estrogen receptor action in breast cancer cells

Fe65 is a multidomain adaptor with established functions in neuronal cells and neurodegeneration diseases. It binds to the C terminus of the Aβ amyloid precursor protein and is involved in regulating gene transcription. The present studies show that Fe65 is expressed in breast cancer (BCa) cells and acts as an ERα transcriptional coregulator that is recruited by 17β-estradiol to the promoters of estrogen target genes. Deletion analyses mapped the ERα binding domain to the phosphotyrosine binding domain 2 (PTB2). Ectopic Fe65 increased the transcriptional activity of the ERα in a PTB2-dependent manner in reporter assays. Fe65 knockdown decreased, whereas its stable expression increased the transcriptional activity of endogenous ERα in BCa cells and the ability of estrogens to stimulate target gene expression, ERα, and coactivator recruitment to target gene promoters and cell growth. Furthermore, Fe65 expression decreased the antagonistic activity of tamoxifen (TAM), suggesting a role for Fe65 in TAM resistance. Overall, the studies define a novel role for the neuronal adaptor in estrogen actions in BCa cells.

FE65 interacts with ADP-ribosylation factor 6 to promote neurite outgrowth

FE65 is an adaptor protein that binds to the amyloid precursor protein (APP). As such, FE65 has been implicated in the pathogenesis of Alzheimer's disease. In addition, evidence suggests that FE65 is involved in brain development. It is generally believed that FE65 participates in these processes by recruiting various interacting partners to form functional complexes. Here, we show that via its first phosphotyrosine binding (PTB) domain, FE65 binds to the small GTPase ADP-ribosylation factor 6 (ARF6). FE65 preferentially binds to ARF6-GDP, and they colocalize in neuronal growth cones. Interestingly, FE65 stimulates the activation of both ARF6 and its downstream GTPase Rac1, a regulator of actin dynamics, and functions in growth cones to stimulate neurite outgrowth. We show that transfection of FE65 and/or ARF6 promotes whereas small interfering RNA knockdown of FE65 or ARF6 inhibits neurite outgrowth in cultured neurons as compared to the mock-transfected control cells. Moreover, knockdown of ARF6 attenuates FE65 stimulation of neurite outgrowth and defective neurite outgrowth seen in FE65-deficient neurons is partially corrected by ARF6 overexpression. Notably, the stimulatory effect of FE65 and ARF6 on neurite outgrowth is abrogated either by dominant-negative Rac1 or knockdown of Rac1. Thus, we identify FE65 as a novel regulator of neurite outgrowth via controlling ARF6-Rac1 signaling.

Amyloid precursor-like protein 2 suppresses irradiation-induced apoptosis in Ewing sarcoma cells and is elevated in immune-evasive Ewing sarcoma cells

Despite surgery, chemotherapy, and radiotherapy treatments, the children, adolescents, and young adults who are diagnosed with metastasized Ewing sarcoma face a dismal prognosis. Amyloid precursor-like protein 2 (APLP2) has recently been implicated in the survival of cancer cells and in our current study, APLP2's contribution to the survival of Ewing sarcoma cells was examined. APLP2 was readily detected in all Ewing sarcoma cell lines analyzed by western blotting, with the TC71 Ewing sarcoma cells expressing the lowest level of APLP2 among the lines. While irradiation induces apoptosis in TC71 Ewing sarcoma cells (as we determined by quantifying the proportion of cells in the sub-G 1 population), transfection of additional APLP2 into TC71 decreased irradiation-induced apoptosis. Consistent with these findings, in parallel studies, we noted that isolates of the TC71 cell line that survived co-culture with lymphokine-activated killer (LAK) cells (which kill by inducing apoptosis in target cells) displayed increased expression of APLP2, in addition to smaller sub-G 1 cell populations after irradiation. Together, these findings suggest that APLP2 lowers the sensitivity of Ewing sarcoma cells to radiotherapy-induced apoptosis and that APLP2 expression is increased in Ewing sarcoma cells able to survive exposure to cytotoxic immune cells.

Immune response profiling identifies autoantibodies specific to Moyamoya patients

Background

Moyamoya Disease is a rare, devastating cerebrovascular disorder characterized by stenosis/occlusion of supraclinoid internal carotid arteries and development of fragile collateral vessels. Moyamoya Disease is typically diagnosed by angiography after clinical presentation of cerebral hemorrhage or ischemia. Despite unclear etiology, previous reports suggest there may be an immunological component.

Methods

To explore the role of autoimmunity in moyamoya disease, we used high-density protein arrays to profile IgG autoantibodies from the sera of angiographically-diagnosed Moyamoya Disease patients and compared these to healthy controls. Protein array data analysis followed by bioinformatics analysis yielded a number of auto-antibodies which were further validated by ELISA for an independent group of MMD patients (n = 59) and control patients with other cerebrovascular diseases including carotid occlusion, carotid stenosis and arteriovenous malformation.

Results

We identified 165 significantly (p < 0.05) elevated autoantibodies in Moyamoya Disease, including those against CAMK2A, CD79A and EFNA3. Pathway analysis associated these autoantibodies with post-translational modification, neurological disease, inflammatory response, and DNA damage repair and maintenance. Using the novel functional interpolating single-nucleotide polymorphisms bioinformatics approach, we identified 6 Moyamoya Disease-associated autoantibodies against APP, GPS1, STRA13, CTNNB1, ROR1 and EDIL3. The expression of these 6 autoantibodies was validated by custom-designed reverse ELISAs for an independent group of Moyamoya Disease patients compared to patients with other cerebrovascular diseases.

Conclusions

We report the first high-throughput analysis of autoantibodies in Moyamoya Disease, the results of which may provide valuable insight into the immune-related pathology of Moyamoya Disease and may potentially advance diagnostic clinical tools.

Connecting chromatin modifying factors to DNA damage response

Cells are constantly damaged by factors that can induce DNA damage. Eukaryotic cells must rapidly load DNA repair proteins onto damaged chromatin during the DNA damage response (DDR). Chromatin-remodeling complexes use the energy from ATP hydrolysis to remodel nucleosomes and have well-established functions in transcription. Emerging lines of evidence indicate that chromatin-remodeling complexes are important and may remodel nucleosomes during DNA damage repair. New studies also reveal that ATP-dependent chromatin remodeling is involved in cell cycle progression, signal transduction pathways, and interaction and modification of DDR-related proteins that are specifically and intimately connected with the process of DNA damage. This article summarizes the recent advances in our understanding of the interplay between chromatin remodeling and DNA damage response.

FE65 regulates and interacts with the Bloom syndrome protein in dynamic nuclear spheres – potential relevance to Alzheimer's disease

The intracellular domain of the amyloid precursor protein (AICD) is generated following cleavage of the precursor by the γ-secretase complex and is involved in membrane to nucleus signaling, for which the binding of AICD to the adapter protein FE65 is essential. Here we show that FE65 knockdown causes a down regulation of the protein BLM and the MCM protein family and that elevated nuclear levels of FE65 result in stabilization of the BLM protein in nuclear mobile spheres. These spheres are able to grow and fuse, and potentially correspond to the nuclear domain 10. BLM plays a role in DNA replication and repair mechanisms and FE65 was also shown to play a role in the cell's response to DNA damage. A set of proliferation assays in our work revealed that FE65 knockdown cells exhibit reduced cell replication in HEK293T cells. On the basis of these results, we hypothesize that nuclear FE65 levels (nuclear FE65/BLM containing spheres) may regulate cell cycle re-entry in neurons due to increased interaction of FE65 with BLM and/or an increase in MCM protein levels. Thus, FE65 interactions with BLM and MCM proteins may contribute to the neuronal cell cycle re-entry observed in Alzheimer disease brains.

Fe65 matters: new light on an old molecule

The discovery that the main constituents of amyloid deposits, characteristic of Alzheimer neuropathology, derive from the proteolytic processing of the membrane precursor amyloid precursor protein (APP) is one of the milestones of the research history of this disease. Despite years of intense studies, the functions of APP and of its amyloidogenic processing are still under debate. One focus of these studies was the complex network of protein-protein interactions centered at the cytosolic domain of APP, which suggests the involvement of APP in a lively signaling pathway. Fe65 was the first protein to be demonstrated to interact with the APP cytodomain. Starting from this observation, a large body of data has been gathered, indicating that Fe65 is an adaptor protein, which binds numerous proteins, further than APP. Among these proteins, the crosstalk with Mena, mDab, and Abl suggested the involvement of the Fe65-APP complex in the regulation of cell motility, with a relevant role in differentiation and development. Other partners, like the histone acetyltransferase Tip60, indicated the possibility that the nuclear fraction of Fe65 could be involved in gene regulation and/or DNA repair.

Radiation-induced alterations in histone modification patterns and their potential impact on short-term radiation effects

Detection and repair of radiation-induced DNA damage occur in the context of chromatin. An intricate network of mechanisms defines chromatin structure, including DNA methylation, incorporation of histone variants, histone modifications, and chromatin remodeling. In the last years it became clear that the cellular response to radiation-induced DNA damage involves all of these mechanisms. Here we focus on the current knowledge on radiation-induced alterations in post-translational histone modification patterns and their effect on the chromatin accessibility, transcriptional regulation and chromosomal stability.

Recognition, signaling, and repair of DNA double-strand breaks produced by ionizing radiation in mammalian cells: the molecular choreography

The faithful maintenance of chromosome continuity in human cells during DNA replication and repair is critical for preventing the conversion of normal diploid cells to an oncogenic state. The evolution of higher eukaryotic cells endowed them with a large genetic investment in the molecular machinery that ensures chromosome stability. In mammalian and other vertebrate cells, the elimination of double-strand breaks with minimal nucleotide sequence change involves the spatiotemporal orchestration of a seemingly endless number of proteins ranging in their action from the nucleotide level to nucleosome organization and chromosome architecture. DNA DSBs trigger a myriad of post-translational modifications that alter catalytic activities and the specificity of protein interactions: phosphorylation, acetylation, methylation, ubiquitylation, and SUMOylation, followed by the reversal of these changes as repair is completed. "Superfluous" protein recruitment to damage sites, functional redundancy, and alternative pathways ensure that DSB repair is extremely efficient, both quantitatively and qualitatively. This review strives to integrate the information about the molecular mechanisms of DSB repair that has emerged over the last two decades with a focus on DSBs produced by the prototype agent ionizing radiation (IR). The exponential growth of molecular studies, heavily driven by RNA knockdown technology, now reveals an outline of how many key protein players in genome stability and cancer biology perform their interwoven tasks, e.g. ATM, ATR, DNA-PK, Chk1, Chk2, PARP1/2/3, 53BP1, BRCA1, BRCA2, BLM, RAD51, and the MRE11-RAD50-NBS1 complex. Thus, the nature of the intricate coordination of repair processes with cell cycle progression is becoming apparent. This review also links molecular abnormalities to cellular pathology as much a possible and provides a framework of temporal relationships.

The amyloid precursor protein intracellular domain-fe65 multiprotein complexes: a challenge to the amyloid hypothesis for Alzheimer's disease?

Since its proposal in 1994, the amyloid cascade hypothesis has prevailed as the mainstream research subject on the molecular mechanisms leading to the Alzheimer's disease (AD). Most of the field had been historically based on the role of the different forms of aggregation of β-amyloid peptide (Aβ). However, a soluble intracellular fragment termed amyloid precursor protein (APP) intracellular domain (AICD) is produced in conjunction with Aβ fragments. This peptide had been shown to be highly toxic in both culture neurons and transgenic mice models. With the advent of this new toxic fragment, the centerpiece for the ethiology of the disease may be changed. This paper discusses the potential role of multiprotein complexes between the AICD and its adapter protein Fe65 and how this could be a potentially important new agent in the neurodegeneration observed in the AD.

Neurodegeneration in Alzheimer disease: role of amyloid precursor protein and presenilin 1 intracellular signaling

Alzheimer disease (AD) is a heterogeneous neurodegenerative disorder characterized by (1) progressive loss of synapses and neurons, (2) intracellular neurofibrillary tangles, composed of hyperphosphorylated Tau protein, and (3) amyloid plaques. Genetically, AD is linked to mutations in few proteins amyloid precursor protein (APP) and presenilin 1 and 2 (PS1 and PS2). The molecular mechanisms underlying neurodegeneration in AD as well as the physiological function of APP are not yet known. A recent theory has proposed that APP and PS1 modulate intracellular signals to induce cell-cycle abnormalities responsible for neuronal death and possibly amyloid deposition. This hypothesis is supported by the presence of a complex network of proteins, clearly involved in the regulation of signal transduction mechanisms that interact with both APP and PS1. In this review we discuss the significance of novel finding related to cell-signaling events modulated by APP and PS1 in the development of neurodegeneration.

Recognition of non-methyl histone marks

Eukaryotic DNA is packaged into chromatin, a complex assembly of protein and nucleic acid. The histones within chromatin undergo extensive, highly regulated post-translational modification. One of the main functions of these modifications is to act as markers that ensure that the mutiprotein complexes that regulate the transcription, replication and repair of DNA are directed to the correct region of the genome at the appropriate time. This review focuses on recent biochemical and structural studies on how histones modified by acetylation, ubiquitination, phosphorylation and poly-ADP-ribosylation are recognized.

Double-strand break-induced transcriptional silencing is associated with loss of tri-methylation at H3K4

Epigenetic alterations induced by ionizing radiation may contribute to radiation carcinogenesis. To detect relative accumulations or losses of constitutive post-translational histone modifications in chromatin regions surrounding DNA double-strand breaks (DSB), we developed a method based on ion microirradiation and correlation of the signal intensities after immunofluorescence detection of the histone modification in question and the DSB marker γ-H2AX. We observed after ionizing irradiation markers for transcriptional silencing, such as accumulation of H3K27me3 and loss of active RNA polymerase II, at chromatin regions labeled by γ-H2AX. Confocal microscopy of whole nuclei and of ultrathin nuclear sections revealed that the histone modification H3K4me3, which labels transcriptionally active regions, is underrepresented in γ-H2AX foci. While some exclusion of H3K4me3 is already evident at the earliest time amenable to this kind of analysis, the anti-correlation apparently increases with time after irradiation, suggesting an active removal process. Focal accumulation of the H3K4me3 demethylase, JARID1A, was observed at damaged regions inflicted by laser irradiation, suggesting involvement of this enzyme in the DNA damage response. Since no accumulation of the repressive mark H3K9me2 was found at damaged sites, we suggest that DSB-induced transcriptional silencing resembles polycomb-mediated silencing rather than heterochromatic silencing.

Regulation of septin dynamics by the Saccharomyces cerevisiae lysine acetyltransferase NuA4

In the budding yeast Saccharomyces cerevisiae, the lysine acetyltransferase NuA4 has been linked to a host of cellular processes through the acetylation of histone and non-histone targets. To discover proteins regulated by NuA4-dependent acetylation, we performed genome-wide synthetic dosage lethal screens to identify genes whose overexpression is toxic to non-essential NuA4 deletion mutants. The resulting genetic network identified a novel link between NuA4 and septin proteins, a group of highly conserved GTP-binding proteins that function in cytokinesis. We show that acetyltransferase-deficient NuA4 mutants have defects in septin collar formation resulting in the development of elongated buds through the Swe1-dependent morphogenesis checkpoint. We have discovered multiple sites of acetylation on four of the five yeast mitotic septins, Cdc3, Cdc10, Cdc12 and Shs1, and determined that NuA4 can acetylate three of the four in vitro. In vivo we find that acetylation levels of both Shs1 and Cdc10 are reduced in a catalytically inactive esa1 mutant. Finally, we determine that cells expressing a Shs1 protein with decreased acetylation in vivo have defects in septin localization that are similar to those observed in NuA4 mutants. These findings provide the first evidence that yeast septin proteins are acetylated and that NuA4 impacts septin dynamics.

Homologous recombination in cancer development, treatment and development of drug resistance

Although DNA double-strand breaks (DSBs) are substrates for homologous recombination (HR) repair, it is becoming apparent that DNA lesions produced at replication forks, for instance by many anticancer drugs, are more significant substrates for HR repair. Cells defective in HR are hypersensitive to a wide variety of anticancer drugs, including those that do not produce DSBs. Several cancers have mutations in or epigenetically silenced HR genes, which explain the genetic instability that drives cancer development. There are an increasing number of reports suggesting that mutation or epigenetic silencing of HR genes explains the sensitivity of cancers to current chemotherapy treatments. Furthermore, there are also many examples of re-expression of HR genes in tumours to explain drug resistance. Emerging data suggest that there are several different subpathways of HR, which can compensate for each other. Unravelling the overlapping pathways in HR showed that BRCA1- and BRCA2-defective cells rely on the PARP protein for survival. This synthetic lethal interaction is now being exploited for selective treatment of BRCA1- and BRCA2-defective cancers with PARP inhibitors. Here, I discuss the diversity of HR and how it impacts on cancer with a particular focus on how HR can be exploited in future anticancer strategies.

Pharmacology of epigenetics in brain disorders

Epigenetics is a rapidly growing field and holds great promise for a range of human diseases, including brain disorders such as Rett syndrome, anxiety and depressive disorders, schizophrenia, Alzheimer disease and Huntington disease. This review is concerned with the pharmacology of epigenetics to treat disorders of the epigenome whether induced developmentally or manifested/acquired later in life. In particular, we will focus on brain disorders and their treatment by drugs that modify the epigenome. While the use of DNA methyl transferase inhibitors and histone deacetylase inhibitors in in vitro and in vivo models have demonstrated improvements in disease-related deficits, clinical trials in humans have been less promising. We will address recent advances in our understanding of the complexity of the epigenome with its many molecular players, and discuss evidence for a compromised epigenome in the context of an ageing or diseased brain. We will also draw on examples of species differences that may exist between humans and model systems, emphasizing the need for more robust pre-clinical testing. Finally, we will discuss fundamental issues to be considered in study design when targeting the epigenome.

Epigenetic mechanisms in neurological diseases: genes, syndromes, and therapies

Epigenetic mechanisms such as DNA methylation and modifications to histone proteins regulate high-order DNA structure and gene expression. Aberrant epigenetic mechanisms are involved in the development of many diseases, including cancer. The neurological disorder most intensely studied with regard to epigenetic changes is Rett syndrome; patients with Rett syndrome have neurodevelopmental defects associated with mutations in MeCP2, which encodes the methyl CpG binding protein 2, that binds to methylated DNA. Other mental retardation disorders are also linked to the disruption of genes involved in epigenetic mechanisms; such disorders include alpha thalassaemia/mental retardation X-linked syndrome, Rubinstein-Taybi syndrome, and Coffin-Lowry syndrome. Moreover, aberrant DNA methylation and histone modification profiles of discrete DNA sequences, and those at a genome-wide level, have just begun to be described for neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, and in other neurological disorders such as multiple sclerosis, epilepsy, and amyotrophic lateral sclerosis. In this Review, we describe epigenetic changes present in neurological diseases and discuss the therapeutic potential of epigenetic drugs, such as histone deacetylase inhibitors.

Identification of histone methylation multiplicities patterns in the brain of senescence-accelerated prone mouse 8

Histone post-translational modifications (PTMs) are involved in diverse biological processes and methylation was regarded as a long-term epigenetic mark. Though aging represented one of the major risk factors for neurodegenerative diseases, no systematic investigations had correlated the patterns of histone PTMs in the brain with aging and the roles of such concerted histone PTMs in brain aging are still unknown. In this study, enzyme digestion, nano-LC, MALDI-TOF/TOF MS analysis and Western blotting were combined to investigate the defined methylation of core histones (H2A, H2B, H3 and H4) in the brain of 12-month-old senescence accelerated mouse prone 8 (SAMP8). The expression of several modified histones in the brain of 3-, and 12-month-old SAMP8 mice as well as that of the age-matched control senescence accelerated-resistant mouse (SAMR1) was compared. In the brain of 12-month-old SAMP8 mice, seven methylation sites (H3K24, H3K27, H3K36, H3K79, H3R128, H4K20 and H2A R89) were detected and most PTMs sites were located on histone H3. Mono-methylated H4K20 decreased significantly in the brain of 12-month-old SAMP8 mice. Methylated H3K27 and H3K36 coexisted in the aged brain with different methylation multiplicities. Di-methylated H3K79 expressed in the neurons of cerebral cortex and hippocampus. This study showed histone methylation patterns in the aged SAMP8 mice brain and provided the experimental evidences for further research on histone PTMs in the aged brain. We hope these results could initiate a platform for the exchange of comprehensive information concerning aging or neurodegenerative disease and help us interpret the change of gene expression and DNA repair ability at epigenetic level.