Transforming growth factor-beta-induced transcription of the Alzheimer beta-amyloid precursor protein gene involves interaction between the CTCF-complex and Smads

Amyloid precursor protein induces reactive astrogliosis

AIM

Astrocytes respond to stressors by acquiring a reactive state characterized by changes in their morphology and function. Molecules underlying reactive astrogliosis, however, remain largely unknown. Given that several studies observed increase in the Amyloid Precursor Protein (APP) in reactive astrocytes, we here test whether APP plays a role in reactive astrogliosis.

METHODS

We investigated whether APP instigates reactive astroglios by examining in vitro and in vivo the morphology and function of naive and APP-deficient astrocytes in response to APP and well-established stressors.

RESULTS

Overexpression of APP in cultured astrocytes led to remodeling of the intermediate filament network, enhancement of cytokine production, and activation of cellular programs centered around the interferon (IFN) pathway, all signs of reactive astrogliosis. Conversely, APP deletion abrogated remodeling of the intermediate filament network and blunted expression of IFN-stimulated gene products in response to lipopolysaccharide. Following traumatic brain injury (TBI), mouse reactive astrocytes also exhibited an association between APP and IFN, while APP deletion curbed the increase in glial fibrillary acidic protein observed canonically in astrocytes in response to TBI.

CONCLUSIONS

The APP thus represents a candidate molecular inducer and regulator of reactive astrogliosis. This finding has implications for understanding pathophysiology of neurodegenerative and other diseases of the nervous system characterized by reactive astrogliosis and opens potential new therapeutic avenues targeting APP and its pathways to modulate reactive astrogliosis.

Exploring the association between cancer and cognitive impairment in the Australian Imaging Biomarkers and Lifestyle (AIBL) study

An inverse association between cancer and Alzheimer's disease (AD) has been demonstrated; however, the association between cancer and mild cognitive impairment (MCI), and the association between cancer and cognitive decline are yet to be clarified. The AIBL dataset was used to address these knowledge gaps. The crude and adjusted odds ratios for MCI/AD and cognitive decline were compared between participants with/without cancer (referred to as C+ and C- participants). A 37% reduction in odds for AD was observed in C+ participants compared to C- participants after adjusting for all confounders. The overall risk for MCI and AD in C+ participants was reduced by 27% and 31%, respectively. The odds of cognitive decline from MCI to AD was reduced by 59% in C+ participants after adjusting for all confounders. The risk of cognitive decline from MCI to AD was halved in C+ participants. The estimated mean change in Clinical Dementia Rating-Sum of boxes (CDR-SOB) score per year was 0.23 units/year higher in C- participants than in C+ participants. Overall, an inverse association between cancer and MCI/AD was observed in AIBL, which is in line with previous reports. Importantly, an inverse association between cancer and cognitive decline has also been identified.

The interaction between ageing and Alzheimer's disease: insights from the hallmarks of ageing

Ageing is a crucial risk factor for Alzheimer's disease (AD) and is characterised by systemic changes in both intracellular and extracellular microenvironments that affect the entire body instead of a single organ. Understanding the specific mechanisms underlying the role of ageing in disease development can facilitate the treatment of ageing-related diseases, such as AD. Signs of brain ageing have been observed in both AD patients and animal models. Alleviating the pathological changes caused by brain ageing can dramatically ameliorate the amyloid beta- and tau-induced neuropathological and memory impairments, indicating that ageing plays a crucial role in the pathophysiological process of AD. In this review, we summarize the impact of several age-related factors on AD and propose that preventing pathological changes caused by brain ageing is a promising strategy for improving cognitive health.

Is There a Role of Vitamin D in Alzheimer's Disease?

Alzheimer's disease (AD) represents the most prevalent type of neurodegenerative dementia and the sixth leading cause of death worldwide. The so-called "non-calcemic actions" of vitamin D have been increasingly described, and its insufficiency has already been linked to the onset and progression of the main neurological diseases, including AD. Immune-mediated Aβ plaque's phagocytosis and clearance, immune response, oxidative stress, and mitochondrial function are all influenced by vitamin D, and these functions are considered relevant in AD pathogenesis. However, it has been shown that the genomic vitamin D signaling pathway is already impaired in the AD brain, making things more complicated. In this paper, we aim to summarise the role of vitamin D in AD and review the results of the supplementation trials in AD patients.

Amyloid precursor protein induces reactive astrogliosis

We present in vitro and in vivo evidence demonstrating that Amyloid Precursor Protein (APP) acts as an essential instigator of reactive astrogliosis. Cell-specific overexpression of APP in cultured astrocytes led to remodelling of the intermediate filament network, enhancement of cytokine production and activation of cellular programs centred around the interferon (IFN) pathway, all signs of reactive astrogliosis. Conversely, APP deletion in cultured astrocytes abrogated remodelling of the intermediate filament network and blunted expression of IFN stimulated gene (ISG) products in response to lipopolysaccharide (LPS). Following traumatic brain injury (TBI), mouse reactive astrocytes also exhibited an association between APP and IFN, while APP deletion curbed the increase in glial fibrillary acidic protein (GFAP) observed canonically in astrocytes in response to TBI. Thus, APP represents a molecular inducer and regulator of reactive astrogliosis.

TGF-β1 signalling in Alzheimer's pathology and cytoskeletal reorganization: a specialized Tau perspective

Microtubule-associated protein, Tau has been implicated in Alzheimer's disease for its detachment from microtubules and formation of insoluble intracellular aggregates within the neurons. Recent findings have suggested the expulsion of Tau seeds in the extracellular domain and their prion-like propagation between neurons. Transforming Growth Factor-β1 (TGF-β1) is a ubiquitously occurring cytokine reported to carry out immunomodulation and neuroprotection in the brain. TGF-β-mediated regulation occurs at the level of neuronal survival and differentiation, glial activation (astrocyte and microglia), amyloid production-distribution-clearance and neurofibrillary tangle formation, all of which contributes to Alzheimer's pathophysiology. Its role in the reorganization of cytoskeletal architecture and remodelling of extracellular matrix to facilitate cellular migration has been well-documented. Microglia are the resident immune sentinels of the brain responsible for surveying the local microenvironment, migrating towards the beacon of pertinent damage and phagocytosing the cellular debris or patho-protein deposits at the site of insult. Channelizing microglia to target extracellular Tau could be a good strategy to combat the prion-like transmission and seeding problem in Alzheimer's disease. The current review focuses on reaffirming the role of TGF-β1 signalling in Alzheimer's pathology and cytoskeletal reorganization and considers utilizing the approach of TGF-β-triggered microglia-mediated targeting of extracellular patho-protein, Tau, as a possible potential strategy to combat Alzheimer's disease.

Combined metabolic activators improve cognitive functions in Alzheimer's disease patients: a randomised, double-blinded, placebo-controlled phase-II trial

BACKGROUND

Alzheimer's disease (AD) is associated with metabolic abnormalities linked to critical elements of neurodegeneration. We recently administered combined metabolic activators (CMA) to the AD rat model and observed that CMA improves the AD-associated histological parameters in the animals. CMA promotes mitochondrial fatty acid uptake from the cytosol, facilitates fatty acid oxidation in the mitochondria, and alleviates oxidative stress.

METHODS

Here, we designed a randomised, double-blinded, placebo-controlled phase-II clinical trial and studied the effect of CMA administration on the global metabolism of AD patients. One-dose CMA included 12.35 g L-serine (61.75%), 1 g nicotinamide riboside (5%), 2.55 g N-acetyl-L-cysteine (12.75%), and 3.73 g L-carnitine tartrate (18.65%). AD patients received one dose of CMA or placebo daily during the first 28 days and twice daily between day 28 and day 84. The primary endpoint was the difference in the cognitive function and daily living activity scores between the placebo and the treatment arms. The secondary aim of this study was to evaluate the safety and tolerability of CMA. A comprehensive plasma metabolome and proteome analysis was also performed to evaluate the efficacy of the CMA in AD patients.

RESULTS

We showed a significant decrease of AD Assessment Scale-cognitive subscale (ADAS-Cog) score on day 84 vs day 0 (P = 0.00001, 29% improvement) in the CMA group. Moreover, there was a significant decline (P = 0.0073) in ADAS-Cog scores (improvement of cognitive functions) in the CMA compared to the placebo group in patients with higher ADAS-Cog scores. Improved cognitive functions in AD patients were supported by the relevant alterations in the hippocampal volumes and cortical thickness based on imaging analysis. Moreover, the plasma levels of proteins and metabolites associated with NAD + and glutathione metabolism were significantly improved after CMA treatment.

CONCLUSION

Our results indicate that treatment of AD patients with CMA can lead to enhanced cognitive functions and improved clinical parameters associated with phenomics, metabolomics, proteomics and imaging analysis. Trial registration ClinicalTrials.gov NCT04044131 Registered 17 July 2019, https://clinicaltrials.gov/ct2/show/NCT04044131.

Amyloid beta accumulations and enhanced neuronal differentiation in cerebral organoids of Dutch-type cerebral amyloid angiopathy patients

Introduction

ADutch-type cerebral amyloid angiopathy (D-CAA) is a hereditary brain disorder caused by a point mutation in the amyloid precursor protein (APP) gene. The mutation is located within the amyloid beta (Aβ) domain of APP and leads to Aβ peptide accumulation in and around the cerebral vasculature. There lack of disease models to study the cellular and molecular pathological mechanisms of D-CAA together with the absence of a disease phenotype in vitro in overexpression cell models, as well as the limited availability of D-CAA animal models indicates the need for a D-CAA patient-derived model.

Methods

We generated cerebral organoids from four D-CAA patients and four controls, cultured them up to 110 days and performed immunofluorescent and targeted gene expression analyses at two time points (D52 and D110).

Results

D-CAA cerebral organoids exhibited Aβ accumulations, showed enhanced neuronal and astrocytic gene expression and TGFβ pathway de-regulation.

Conclusions

These results illustrate the potential of cerebral organoids as in vitro disease model of D-CAA that can be used to understand disease mechanisms of D-CAA and can serve as therapeutic intervention platform for various Aβ-related disorders.

Vitamin D in Neurological Diseases

Vitamin D may have multiple effects on the nervous system and its deficiency can represent a possible risk factor for the development of many neurological diseases. Recent studies are also trying to clarify the different effects of vitamin D supplementation over the course of progressive neurological diseases. In this narrative review, we summarise vitamin D chemistry, metabolism, mechanisms of action, and the recommended daily intake. The role of vitamin D on gene transcription and the immune response is also reviewed. Finally, we discuss the scientific evidence that links low 25-hydroxyvitamin D concentrations to the onset and progression of severe neurological diseases, such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, migraine, diabetic neuropathy and amyotrophic lateral sclerosis. Completed and ongoing clinical trials on vitamin D supplementation in neurological diseases are listed.

Transcriptional and Post-Transcriptional Regulations of Amyloid-β Precursor Protein (APP) mRNA

Alzheimer’s disease (AD) is an age-associated neurodegenerative disorder characterized by progressive impairment of memory, thinking, behavior, and dementia. Based on ample evidence showing neurotoxicity of amyloid-β (Aβ) aggregates in AD, proteolytically derived from amyloid precursor protein (APP), it has been assumed that misfolding of Aβ plays a crucial role in the AD pathogenesis. Additionally, extra copies of the APP gene caused by chromosomal duplication in patients with Down syndrome can promote AD pathogenesis, indicating the pathological involvement of the APP gene dose in AD. Furthermore, increased APP expression due to locus duplication and promoter mutation of APP has been found in familial AD. Given this background, we aimed to summarize the mechanism underlying the upregulation of APP expression levels from a cutting-edge perspective. We first reviewed the literature relevant to this issue, specifically focusing on the transcriptional regulation of APP by transcription factors that bind to the promoter/enhancer regions. APP expression is also regulated by growth factors, cytokines, and hormone, such as androgen. We further evaluated the possible involvement of post-transcriptional regulators of APP in AD pathogenesis, such as RNA splicing factors. Indeed, alternative splicing isoforms of APP are proposed to be involved in the increased production of Aβ. Moreover, non-coding RNAs, including microRNAs, post-transcriptionally regulate the APP expression. Collectively, elucidation of the novel mechanisms underlying the upregulation of APP would lead to the development of clinical diagnosis and treatment of AD.

Oncogenic Pathways in Neurodegenerative Diseases

Cancer and neurodegenerative diseases are two of the leading causes of premature death in modern societies. Their incidence continues to increase, and in the near future, it is believed that cancer will kill more than 20 million people per year, and neurodegenerative diseases, due to the aging of the world population, will double their prevalence. The onset and the progression of both diseases are defined by dysregulation of the same molecular signaling pathways. However, whereas in cancer, these alterations lead to cell survival and proliferation, neurodegenerative diseases trigger cell death and apoptosis. The study of the mechanisms underlying these opposite final responses to the same molecular trigger is key to providing a better understanding of the diseases and finding more accurate treatments. Here, we review the ten most common signaling pathways altered in cancer and analyze them in the context of different neurodegenerative diseases such as Alzheimer's (AD), Parkinson's (PD), and Huntington's (HD) diseases.

Systematic review of human post-mortem immunohistochemical studies and bioinformatics analyses unveil the complexity of astrocyte reaction in Alzheimer's disease

AIMS

Reactive astrocytes in Alzheimer's disease (AD) have traditionally been demonstrated by increased glial fibrillary acidic protein (GFAP) immunoreactivity; however, astrocyte reaction is a complex and heterogeneous phenomenon involving multiple astrocyte functions beyond cytoskeletal remodelling. To better understand astrocyte reaction in AD, we conducted a systematic review of astrocyte immunohistochemical studies in post-mortem AD brains followed by bioinformatics analyses on the extracted reactive astrocyte markers.

METHODS

NCBI PubMed, APA PsycInfo and WoS-SCIE databases were interrogated for original English research articles with the search terms 'Alzheimer's disease' AND 'astrocytes.' Bioinformatics analyses included protein-protein interaction network analysis, pathway enrichment, and transcription factor enrichment, as well as comparison with public human -omics datasets.

RESULTS

A total of 306 articles meeting eligibility criteria rendered 196 proteins, most of which were reported to be upregulated in AD vs control brains. Besides cytoskeletal remodelling (e.g., GFAP), bioinformatics analyses revealed a wide range of functional alterations including neuroinflammation (e.g., IL6, MAPK1/3/8 and TNF), oxidative stress and antioxidant defence (e.g., MT1A/2A, NFE2L2, NOS1/2/3, PRDX6 and SOD1/2), lipid metabolism (e.g., APOE, CLU and LRP1), proteostasis (e.g., cathepsins, CRYAB and HSPB1/2/6/8), extracellular matrix organisation (e.g., CD44, MMP1/3 and SERPINA3), and neurotransmission (e.g., CHRNA7, GABA, GLUL, GRM5, MAOB and SLC1A2), among others. CTCF and ESR1 emerged as potential transcription factors driving these changes. Comparison with published -omics datasets validated our results, demonstrating a significant overlap with reported transcriptomic and proteomic changes in AD brains and/or CSF.

CONCLUSIONS

Our systematic review of the neuropathological literature reveals the complexity of AD reactive astrogliosis. We have shared these findings as an online resource available at www.astrocyteatlas.org.

MicroRNA-455-3p as a Potential Biomarker for Alzheimer's Disease: An Update

A non-invasive and early-detectable peripheral biomarker is urgently needed for Alzheimer's disease (AD). The present study is a step forward to verify the biomarker properties of human microRNA-455-3p (Hsa-miR-455-3p) in AD patients. Our previous findings on mild cognitive impaired subjects, AD patients and AD cells and mouse models unveiled the miR-455-3p as a potential peripheral biomarker for AD. In the current study, we verified the differential expression of miR-455-3p in postmortem AD brains obtained from NIH NeuroBioBank, and fibroblasts and B-lymphocytes from both familial and sporadic AD patients from Coriell Cell Repository of National Institutes on Aging. Total RNA was extracted from the fibroblasts, B-lymphocytes and AD postmortem brains, and expression of miR-455-3p was measured by real-time reverse-transcriptase RT-PCR. Our real-time RT-PCR analysis showed a significant (P = 0.0002) upregulation of miR-455-3p expression in AD postmortem brains compared to healthy control samples. Expression of miR-455-3p was also upregulated in the fibroblasts from AD patients, however a significant difference in miR-455-3p level was observed in the cells from sporadic AD patients (P = 0.014) compared to healthy controls. Similarly, in B-lymphocytes, miR-455-3p level was also higher (P = 0.044) especially in sporadic AD cases compared to controls. Receiver operating characteristic (ROC) curve analysis indicated the significant area under ROC curve (AUROC) value of miR-455-3p in AD postmortem brain (AUROC = 0.792; P = 0.001) and AD fibroblasts cells (AUROC = 0.861; P = 0.03), whereas in B-lymphocytes AUROC value of miR-455-3p was not significant. Further, in-silico analysis for miRNA targets predictions showed the binding capacity of miR-455-3p with several AD associated key genes such as APP, NGF, USP25, PDRG1, SMAD4, UBQLN1, SMAD2, TP73, VAMP2, HSPBAP1, and NRXN1. Hence, these observations further revealed that miR-455-3p is a potential biomarker for AD and its possible therapeutic target for AD.

Glial Draper Rescues Aβ Toxicity in a Drosophila Model of Alzheimer's Disease

Pathological hallmarks of Alzheimer's disease (AD) include amyloid-β (Aβ) plaques, neurofibrillary tangles, and reactive gliosis. Glial cells offer protection against AD by engulfing extracellular Aβ peptides, but the repertoire of molecules required for glial recognition and destruction of Aβ are still unclear. Here, we show that the highly conserved glial engulfment receptor Draper/MEGF10 provides neuroprotection in an AD model of Drosophila (both sexes). Neuronal expression of human Aβ42^arc in adult flies results in robust Aβ accumulation, neurodegeneration, locomotor dysfunction, and reduced lifespan. Notably, all of these phenotypes are more severe in draper mutant animals, whereas enhanced expression of glial Draper reverses Aβ accumulation, as well as behavioral phenotypes. We also show that the signal transducer and activator of transcription (Stat92E), c-Jun N-terminal kinase (JNK)/AP-1 signaling, and expression of matrix metalloproteinase-1 (Mmp1) are activated downstream of Draper in glia in response to Aβ42^arc exposure. Furthermore, Aβ42-induced upregulation of the phagolysosomal markers Atg8 and p62 was notably reduced in draper mutant flies. Based on our findings, we propose that glia clear neurotoxic Aβ peptides in the AD model Drosophila brain through a Draper/STAT92E/JNK cascade that may be coupled to protein degradation pathways such as autophagy or more traditional phagolysosomal destruction methods.SIGNIFICANCE STATEMENT Alzheimer's disease (AD) and similar dementias are common incurable neurodegenerative disorders in the aging population. As the primary immune responders in the brain, glial cells are implicated as key players in the onset and progression of AD and related disorders. Here we show that the glial engulfment receptor Draper is protective in a Drosophila model of AD, reducing levels of amyloid β (Aβ) peptides, reversing locomotor defects, and extending lifespan. We further show that protein degradation pathways are induced downstream of Draper in AD model flies, supporting a model in which glia engulf and destroy Aβ peptides to reduce amyloid-associated toxicity.

MeCP2 and CTCF: enhancing the cross-talk of silencers

This paper provides a brief introductory review of the most recent advances in our knowledge about the structural and functional aspects of two transcriptional regulators: MeCP2, a protein whose mutated forms are involved in Rett syndrome; and CTCF, a constitutive transcriptional insulator. This is followed by a description of the PTMs affecting these two proteins and an analysis of their known interacting partners. A special emphasis is placed on the recent studies connecting these two proteins, focusing on the still poorly understood potential structural and functional interactions between the two of them on the chromatin substrate. An overview is provided for some of the currently known genes that are dually regulated by these two proteins. Finally, a model is put forward to account for their possible involvement in their regulation of gene expression.

TGFβ pathway deregulation and abnormal phospho-SMAD2/3 staining in hereditary cerebral hemorrhage with amyloidosis-Dutch type

Hereditary cerebral hemorrhage with amyloidosis‐Dutch type (HCHWA‐D) is an early onset hereditary form of cerebral amyloid angiopathy (CAA) pathology, caused by the E22Q mutation in the amyloid β (Aβ) peptide. Transforming growth factor β1 (TGFβ1) is a key player in vascular fibrosis and in the formation of angiopathic vessels in transgenic mice. Therefore, we investigated whether the TGFβ pathway is involved in HCHWA‐D pathogenesis in human postmortem brain tissue from frontal and occipital lobes. Components of the TGFβ pathway were analyzed with quantitative RT‐PCR. TGFβ1 and TGFβ Receptor 2 (TGFBR2) gene expression levels were significantly increased in HCHWA‐D in comparison to the controls, in both frontal and occipital lobes. TGFβ‐induced pro‐fibrotic target genes were also upregulated. We further assessed pathway activation by detecting phospho‐SMAD2/3 (pSMAD2/3), a direct TGFβ down‐stream signaling mediator, using immunohistochemistry. We found abnormal pSMAD2/3 granular deposits specifically on HCHWA‐D angiopathic frontal and occipital vessels. We graded pSMAD2/3 accumulation in angiopathic vessels and found a positive correlation with the CAA load independent of the brain area. We also observed pSMAD2/3 granules in a halo surrounding occipital vessels, which was specific for HCHWA‐D. The result of this study indicates an upregulation of TGFβ1 in HCHWA‐D, as was found previously in AD with CAA pathology. We discuss the possible origins and implications of the TGFβ pathway deregulation in the microvasculature in HCHWA‐D. These findings identify the TGFβ pathway as a potential biomarker of disease progression and a possible target of therapeutic intervention in HCHWA‐D.

Alpha-Smooth Muscle Actin mRNA and Protein Are Increased in Isolated Brain Vessel Extracts of Alzheimer Mice

Alzheimer's disease (AD) is a severe neurodegenerative disorder of the brain, characterized by extracellular beta-amyloid (Aβ) plaques, intracellular tau pathology, neurodegeneration and inflammation. There is clear evidence that the blood-brain barrier is damaged in AD and that vessel function is impaired. Alpha-smooth muscle actin (αSMA) is a prominent protein expressed on brain vessels, especially in cells located closer to the arteriole end of the capillaries, which possibly influences the blood vessel contraction. The aim of the present study was to observe αSMA protein and mRNA expression in isolated brain vessel extracts and cortex in an Alzheimer mouse model with strong Aβ plaque deposition. Our data revealed a prominent expression of αSMA protein in isolated brain vessel extracts of AD mice by Western blot analysis. Immunostaining showed that these vessels were associated with Aβ plaques. Quantitative real-time PCR analysis confirmed this increase at the mRNA expression level and showed a significant increase of transforming growth factor beta-1 mRNA expression in AD mice. In situ hybridization demonstrated a strong expression pattern of αSMA mRNA in the whole cortex and hippocampus. In conclusion, our data provide evidence that αSMA protein and mRNA are enhanced in vessels in an AD mouse model, possibly counteracting vessel malfunction in AD.

CTCF-dependent co-localization of canonical Smad signaling factors at architectural protein binding sites in D. melanogaster

The transforming growth factor β (TGF-β) and bone morphogenetic protein (BMP) pathways transduce extracellular signals into tissue-specific transcriptional responses. During this process, signaling effector Smad proteins translocate into the nucleus to direct changes in transcription, but how and where they localize to DNA remain important questions. We have mapped Drosophila TGF-β signaling factors Mad, dSmad2, Medea, and Schnurri genome-wide in Kc cells and find that numerous sites for these factors overlap with the architectural protein CTCF. Depletion of CTCF by RNAi results in the disappearance of a subset of Smad sites, suggesting Smad proteins localize to CTCF binding sites in a CTCF-dependent manner. Sensitive Smad binding sites are enriched at low occupancy CTCF peaks within topological domains, rather than at the physical domain boundaries where CTCF may function as an insulator. In response to Decapentaplegic, CTCF binding is not significantly altered, whereas Mad, Medea, and Schnurri are redirected from CTCF to non-CTCF binding sites. These results suggest that CTCF participates in the recruitment of Smad proteins to a subset of genomic sites and in the redistribution of these proteins in response to BMP signaling.

Role of TGFβ signaling in the pathogenesis of Alzheimer's disease

Aging is the main risk factor for Alzheimer’s disease (AD); being associated with conspicuous changes on microglia activation. Aged microglia exhibit an increased expression of cytokines, exacerbated reactivity to various stimuli, oxidative stress, and reduced phagocytosis of β-amyloid (Aβ). Whereas normal inflammation is protective, it becomes dysregulated in the presence of a persistent stimulus, or in the context of an inflammatory environment, as observed in aging. Thus, neuroinflammation can be a self-perpetuating deleterious response, becoming a source of additional injury to host cells in neurodegenerative diseases. In aged individuals, although transforming growth factor β (TGFβ) is upregulated, its canonical Smad3 signaling is greatly reduced and neuroinflammation persists. This age-related Smad3 impairment reduces protective activation while facilitating cytotoxic activation of microglia through several cellular mechanisms, potentiating microglia-mediated neurodegeneration. Here, we critically discuss the role of TGFβ-Smad signaling on the cytotoxic activation of microglia and its relevance in the pathogenesis of AD. Other protective functions, such as phagocytosis, although observed in aged animals, are not further induced by inflammatory stimuli and TGFβ1. Analysis in silico revealed that increased expression of receptor scavenger receptor (SR)-A, involved in Aβ uptake and cell activation, by microglia exposed to TGFβ, through a Smad3-dependent mechanism could be mediated by transcriptional co-factors Smad2/3 over the MSR1 gene. We discuss that changes of TGFβ-mediated regulation could at least partially mediate age-associated microglia changes, and, together with other changes on inflammatory response, could result in the reduction of protective activation and the potentiation of cytotoxicity of microglia, resulting in the promotion of neurodegenerative diseases.

WW domain-containing oxidoreductase in neuronal injury and neurological diseases

The human and mouse WWOX/Wwox gene encodes a candidate tumor suppressor WW domain-containing oxidoreductase protein. This gene is located on a common fragile site FRA16D. WWOX participates in a variety of cellular events and acts as a transducer in the many signal pathways, including TNF, chemotherapeutic drugs, UV irradiation, Wnt, TGF-β, C1q, Hyal-2, sex steroid hormones, and others. While transiently overexpressed WWOX restricts relocation of transcription factors to the nucleus for suppressing cancer survival, physiological relevance of this regard in vivo has not been confirmed. Unlike many tumor suppressor genes, mutation of WWOX is rare, raising a question whether WWOX is a driver for cancer initiation. WWOX/Wwox was initially shown to play a crucial role in neural development and in the pathogenesis of Alzheimer's disease and neuronal injury. Later on, WWOX/Wwox was shown to participate in the development of epilepsy, mental retardation, and brain developmental defects in mice, rats and humans. Up to date, most of the research and review articles have focused on the involvement of WWOX in cancer. Here, we review the role of WWOX in neural injury and neurological diseases, and provide perspectives for the WWOX-regulated neurodegeneration.

WWOX dysfunction induces sequential aggregation of TRAPPC6AΔ, TIAF1, tau and amyloid β, and causes apoptosis

Aggregated vesicle-trafficking protein isoform TRAPPC6AΔ (TPC6AΔ) has a critical role in causing caspase activation, tau aggregation and Aβ generation in the brains of nondemented middle-aged humans, patients with Alzheimer's disease (AD) and 3-week-old Wwox gene knockout mice. WWOX blocks neurodegeneration via interactions with tau and tau-phosphorylating enzymes. WWOX deficiency leads to epilepsy, mental retardation and early death. Here, we demonstrated that TGF-β1 induces shuttling of endogenous wild-type TPC6A and TPC6AΔ in between nucleoli and mitochondria (~40-60 min per round trip), and WWOX reduces the shuttling time by 50%. TGF-β1 initially maximizes the binding of TPC6AΔ to the C-terminal tail of WWOX, followed by dissociation. TPC6AΔ then undergoes aggregation, together with TIAF1 (TGF-β1-induced antiapoptotic factor), in the mitochondria to induce apoptosis. An additional rescue scenario is that TGF-β1 induces Tyr33 phosphorylation and unfolding of WWOX and its the N-terminal WW domain slowly binds TPC6AΔ to block aggregation and apoptosis. Similarly, loss of WWOX induces TPC6AΔ polymerization first, then aggregation of TIAF1, amyloid β and tau, and subsequent cell death, suggesting that a cascade of protein aggregation leads to neurodegeneration.

TGF-β1 protection against Aβ1-42-induced neuroinflammation and neurodegeneration in rats

Transforming growth factor (TGF)-β1, a cytokine that can be expressed in the brain, is a key regulator of the brain's responses to injury and inflammation. Alzheimer's disease (AD), the most common neurodegenerative disorder, involves inflammatory processes in the brain in addition to the hallmarks, amyloid-β (Aβ) plaques and neurofibrillary tangles. Recently, we have shown that T-helper (Th) 17 cells, a subpopulation of CD4+ T-cells with high proinflammation, also participate in the brain inflammatory process of AD. However, it is poorly known whether TGF-β1 ameliorates the lymphocyte-mediated neuroinflammation and, thereby, alleviates neurodegeneration in AD. Herein, we administered TGF-β1 via the intracerebroventricle (ICV) in AD model rats, by Aβ1-42 injection in both sides of the hippocampus, to show the neuroprotection of TGF-β1. The TGF-β1 administration after the Aβ1-42 injection ameliorated cognitive deficit and neuronal loss and apoptosis, reduced amyloid precursor protein (APP) expression, elevated protein phosphatase (PP)2A expression, attenuated glial activation and alleviated the imbalance of the pro-inflammatory/anti-inflammatory responses of T-lymphocytes, compared to the Aβ1-42 injection alone. These findings demonstrate that TGF-β1 provides protection against AD neurodegeneration and suggest that the TGF-β1 neuroprotection is implemented by the alleviation of glial and T-cell-mediated neuroinflammation.

Associations of genetic variants in ADAM33 and TGF-β1 genes with childhood asthma risk

The aim of the present study was to explore the associations of genetic variants in the ADAM33 and TGF-β1 genes with the risk of childhood asthma. A total of 299 asthmatic children and 311 healthy controls were recruited in the hospital-based case-control study. The asthmatic subjects were further divided into mild and severe groups according to disease severity. Single-nucleotide polymorphisms (SNP) at ADAM33 V4, T2, S2 and T1, and TGF-β1 C-509T and T869C were selected and detected with PCR-RFLP. The associations of the SNPs with asthma risk and severity were analyzed. The associations between the haplotypes of ADAM33 and TGF-β1 were also evaluated. Compared with the GG genotype, the GC and CC genotypes at V4 were associated with an increased asthma risk in children and the ORs were 2.92 and 10.56, respectively. Compared with the CC genotype, the CT/TT genotype at C-509T was associated with an increased asthma risk and the OR was 2.26. Subsequent to stratification by asthma severity, compared with the V4 GG genotype, it was found that the CG and CC genotypes were associated with a mild asthma risk and the ORs were 3.00 and 5.99, respectively. The SNP at C-509T (CT/TT vs. CC) was associated with mild asthma (OR=2.34), whereas a marginally significant association was detected between the SNP (CT/TT vs. CC) and severe asthma risk (OR=2.19). The haplotype analysis revealed that, compared with the GGCA haplotype of ADAM33, significant associations of the haplotypes of CGCG, CGGA, GACA, GACG and GAGA with asthma risk were observed, and the ORs were 31.12, 12.24, 4.73, 30.85 and 4.83, respectively. No significant association was detected between the TGF-β1 haplotypes and asthma risk. The genetic variants at V4 and C-509T had the potential to modify the childhood asthma risk and the associations showed no notable difference with the disease severity. Thus, ADAM33 haplotypes provided more useful information in the prediction of asthma risk.

CTCF binding site sequence differences are associated with unique regulatory and functional trends during embryonic stem cell differentiation

CTCF (CCCTC-binding factor) is a highly conserved multifunctional DNA-binding protein with thousands of binding sites genome-wide. Our previous work suggested that differences in CTCF’s binding site sequence may affect the regulation of CTCF recruitment and its function. To investigate this possibility, we characterized changes in genome-wide CTCF binding and gene expression during differentiation of mouse embryonic stem cells. After separating CTCF sites into three classes (LowOc, MedOc and HighOc) based on similarity to the consensus motif, we found that developmentally regulated CTCF binding occurs preferentially at LowOc sites, which have lower similarity to the consensus. By measuring the affinity of CTCF for selected sites, we show that sites lost during differentiation are enriched in motifs associated with weaker CTCF binding in vitro. Specifically, enrichment for T at the 18^th position of the CTCF binding site is associated with regulated binding in the LowOc class and can predictably reduce CTCF affinity for binding sites. Finally, by comparing changes in CTCF binding with changes in gene expression during differentiation, we show that LowOc and HighOc sites are associated with distinct regulatory functions. Our results suggest that the regulatory control of CTCF is dependent in part on specific motifs within its binding site.

Role of the Transforming-Growth-Factor-β1 Gene in Late-Onset Alzheimer's Disease: Implications for the Treatment

Late-onset Alzheimer's disease (LOAD) is the most common form of dementia in the elderly. LOAD has a complex and largely unknown etiology with strong genetic determinants. Genetics of LOAD is known to involve several genetic risk factors among which the Apolipoprotein E (APOE) gene seems to be the major recognized genetic determinant. Recent efforts have been made to identify other genetic factors involved in the pathophysiology of LOAD such as genes associated with a deficit of neurotrophic factors in the AD brain. Genetic variations of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), and transforming-growth-factor-β1 (TGF-β1) are known to increase the risk to develop LOAD and have also been related to depression susceptibility in LOAD. Transforming-Growth-Factor-β1 (TGF-β1) is a neurotrophic factor that exerts neuroprotective effects against ß-amyloid-induced neurodegeneration. Recent evidence suggests that a specific impairment in the signaling of TGF-β is an early event in the pathogenesis of AD. TGF-β1 protein levels are predominantly under genetic control, and the TGF-β1 gene, located on chromosome 19q13.1–3, con-tains several single nucleotide polymorphisms (SNPs) upstream and in the transcript region, such as the SNP at codon +10 (T/C) and +25 (G/C), which is known to influence the level of expression of TGF-β1. In the present review, we summarize the current literature on genetic risk factors for LOAD, focusing on the role of the TGF-β1 gene, finally discussing the possible implications of these genetic studies for the selection of patients eligible for neuroprotective strategies in AD.

The role of chromatin insulators in nuclear architecture and genome function

Eukaryotic genomes are intricately arranged into highly organized yet dynamic structures that underlie patterns of gene expression and cellular identity. The recent adaptation of novel genomic strategies for assaying nuclear architecture has significantly extended and accelerated our ability to query the nature of genome organization and the players involved. In particular, recent explorations of physical arrangements and chromatin landscapes in higher eukaryotes have demonstrated that chromatin insulators, which mediate functional interactions between regulatory elements, appear to play an important role in these processes. Here we reflect on current findings and our rapidly expanding understanding of insulators and their role in nuclear architecture and genome function.

Astrocytes as a source for extracellular matrix molecules and cytokines

Research of the past 25 years has shown that astrocytes do more than participating and building up the blood-brain barrier and detoxify the active synapse by reuptake of neurotransmitters and ions. Indeed, astrocytes express neurotransmitter receptors and, as a consequence, respond to stimuli. Within the tripartite synapse, the astrocytes owe more and more importance. Besides the functional aspects the differentiation of astrocytes has gained a more intensive focus. Deeper knowledge of the differentiation processes during development of the central nervous system might help explaining and even help treating neurological diseases like Alzheimer’s disease, Amyotrophic lateral sclerosis, Parkinsons disease, and psychiatric disorders in which astrocytes have been shown to play a role. Specific differentiation of neural stem cells toward the astroglial lineage is performed as a multi-step process. Astrocytes and oligodendrocytes develop from a multipotent stem cell that prior to this has produced primarily neuronal precursor cells. This switch toward the more astroglial differentiation is regulated by a change in receptor composition on the cell surface and responsiveness to Fibroblast growth factor and Epidermal growth factor (EGF). The glial precursor cell is driven into the astroglial direction by signaling molecules like Ciliary neurotrophic factor, Bone Morphogenetic Proteins, and EGF. However, the early astrocytes influence their environment not only by releasing and responding to diverse soluble factors but also express a wide range of extracellular matrix (ECM) molecules, in particular proteoglycans of the lectican family and tenascins. Lately these ECM molecules have been shown to participate in glial development. In this regard, especially the matrix protein Tenascin C (Tnc) proved to be an important regulator of astrocyte precursor cell proliferation and migration during spinal cord development. Nevertheless, ECM molecules expressed by reactive astrocytes are also known to act mostly in an inhibitory fashion under pathophysiological conditions. Thus, we further summarize resent data concerning the role of chondroitin sulfate proteoglycans and Tnc under pathological conditions.

CTCF function is modulated by neighboring DNA binding factors

The zinc-finger protein CTCF was originally identified in the context of gene silencing and gene repression (Baniahmad et al. 1990; Lobanenkov et al. 1990). CTCF was later shown to be involved in several transcriptional mechanisms such as gene activation (Vostrov et al. 2002) and enhancer blocking (Filippova et al. 2001; Hark et al. 2000; Kanduri et al. 2000; Lutz et al. 2003; Szabó et al. 2000; Tanimoto et al. 2003; Phillips and Corces 2009; Bell et al. 1999; Zlatanova and Caiafa 2009a, 2009b). Insulators block the action of enhancers when positioned between enhancer and promoter. CTCF was found to be required in almost all cases of enhancer blocking tested in vertebrates. This CTCF-mediated enhancer blocking is in many instances conferred by constitutive CTCF action. For some examples however, a modulation of the enhancer blocking activity was documented (Lutz et al. 2003; Weth et al. 2010). One mechanism is achieved by regulation of binding to DNA. It was shown that CTCF is not able to bind to those binding-sites containing methylated CpG sequences. At the imprinting control region (ICR) of the Igf2/H19 locus the binding-site for CTCF on the paternal allele is methylated. This prevents DNA-binding of CTCF, resulting in the loss of enhancer blocking (Bell and Felsenfeld 2000; Chao et al. 2002; Filippova et al. 2001; Hark et al. 2000; Kanduri et al. 2000, 2002; Szabó et al. 2000; Takai et al. 2001). Not only can DNA methylation interfere with CTCF binding to DNA, it was also shown in one report that RNA transcription through the CTCF binding site results in CTCF eviction (Lefevre et al. 2008). In contrast to these cases most of the DNA sites are not differentially bound by CTCF. Even CTCF interaction with its cofactor cohesin does not seem to differ in different cell types (Schmidt et al. 2010). These results indicate that regulation of CTCF activity might be achieved by neighboring factors bound to DNA. In fact, whole genome analyses of CTCF binding sites identified several classes of neighboring sequences (Dickson et al. 2010; Boyle et al. 2010; Essien et al. 2009). Therefore, in this review we will summarize those results for which a combined action of CTCF with factors bound adjacently was found. These neighboring factors include the RNA polymerases I, II and III, another zinc finger factor VEZF1 and the factors YY1, SMAD, TR and Oct4. Each of these seems to influence, modulate or determine the function of CTCF. Thereby, at least some of the pleiotropic effects of CTCF can be explained.

TGF-β induces TIAF1 self-aggregation via type II receptor-independent signaling that leads to generation of amyloid β plaques in Alzheimer's disease

The role of a small transforming growth factor beta (TGF-β)-induced TIAF1 (TGF-β1-induced antiapoptotic factor) in the pathogenesis of Alzheimer's disease (AD) was investigated. TIAF1 physically interacts with mothers against DPP homolog 4 (Smad4), and blocks SMAD-dependent promoter activation when overexpressed. Accordingly, knockdown of TIAF1 by small interfering RNA resulted in spontaneous accumulation of Smad proteins in the nucleus and activation of the promoter governed by the SMAD complex. TGF-β1 and environmental stress (e.g., alterations in pericellular environment) may induce TIAF1 self-aggregation in a type II TGF-β receptor-independent manner in cells, and Smad4 interrupts the aggregation. Aggregated TIAF1 induces apoptosis in a caspase-dependent manner. By filter retardation assay, TIAF1 aggregates were found in the hippocampi of nondemented humans and AD patients. Total TIAF1-positive samples containing amyloid β (Aβ) aggregates are 17 and 48%, respectively, in the nondemented and AD groups, suggesting that TIAF1 aggregation occurs preceding formation of Aβ. To test this hypothesis, in vitro analysis showed that TGF-β-regulated TIAF1 aggregation leads to dephosphorylation of amyloid precursor protein (APP) at Thr668, followed by degradation and generation of APP intracellular domain (AICD), Aβ and amyloid fibrils. Polymerized TIAF1 physically interacts with amyloid fibrils, which would favorably support plaque formation in vivo.

Reactive astrocytes as therapeutic targets for CNS disorders

Reactive astrogliosis has long been recognized as a ubiquitous feature of CNS pathologies. Although its roles in CNS pathology are only beginning to be defined, genetic tools are enabling molecular dissection of the functions and mechanisms of reactive astrogliosis in vivo. It is now clear that reactive astrogliosis is not simply an all-or-nothing phenomenon but, rather, is a finely gradated continuum of molecular, cellular, and functional changes that range from subtle alterations in gene expression to scar formation. These changes can exert both beneficial and detrimental effects in a context-dependent manner determined by specific molecular signaling cascades. Dysfunction of either astrocytes or the process of reactive astrogliosis is emerging as an important potential source of mechanisms that might contribute to, or play primary roles in, a host of CNS disorders via loss of normal or gain of abnormal astrocyte activities. A rapidly growing understanding of the mechanisms underlying astrocyte signaling and reactive astrogliosis has the potential to open doors to identifying many molecules that might serve as novel therapeutic targets for a wide range of neurological disorders. This review considers general principles and examines selected examples regarding the potential of targeting specific molecular aspects of reactive astrogliosis for therapeutic manipulations, including regulation of glutamate, reactive oxygen species, and cytokines.

Transforming growth factor beta promotes complexes between Smad proteins and the CCCTC-binding factor on the H19 imprinting control region chromatin

Whether signal transduction pathways regulate epigenetic states in response to environmental cues remains poorly understood. We demonstrate here that Smad3, signaling downstream of transforming growth factor β, interacts with the zinc finger domain of CCCTC-binding factor (CTCF), a nuclear protein known to act as “the master weaver of the genome.” This interaction occurs via the Mad homology 1 domain of Smad3. Although Smad2 and Smad4 fail to interact, an alternatively spliced form of Smad2 lacking exon 3 interacts with CTCF. CTCF does not perturb well established transforming growth factor β gene responses. However, Smads and CTCF co-localize to the H19 imprinting control region (ICR), which emerges as an insulator in cis and regulator of transcription and replication in trans via direct CTCF binding to the ICR. Smad recruitment to the ICR requires intact CTCF binding to this locus. Smad2/3 binding to the ICR requires Smad4, which potentially provides stability to the complex. Because the CTCF-Smad complex is not essential for the chromatin insulator function of the H19 ICR, we propose that it can play a role in chromatin cross-talk organized by the H19 ICR.

TGF-β1 pathway as a new target for neuroprotection in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 37 million people worldwide. Current drugs for AD are only symptomatic, but do not interfere with the underlying pathogenic mechanisms of the disease. AD is characterized by the presence of ß-amyloid (Aβ) plaques, neurofibrillary tangles, and neuronal loss. The identification of the molecular determinants underlying AD pathogenesis is a fundamental step to design new disease-modifying drugs. Recently, a specific impairment of transforming-growth-factor-β1 (TGF-β1) signaling pathway has been demonstrated in AD brain. The deficiency of TGF-β1 signaling has been shown to increase both Aβ accumulation and Aβ-induced neurodegeneration in AD models. The loss of function of TGF-ß1 pathway seems also to contribute to tau pathology and neurofibrillary tangle formation. Growing evidence suggests a neuroprotective role for TGF-β1 against Aβ toxicity both in vitro and in vivo models of AD. Different drugs, such as lithium or group II mGlu receptor agonists are able to increase TGF-β1 levels in the central nervous system (CNS), and might be considered as new neuroprotective tools against Aβ-induced neurodegeneration. In the present review, we examine the evidence for a neuroprotective role of TGF-β1 in AD, and discuss the TGF-β1 signaling pathway as a new pharmacological target for the treatment of AD.

Calcium signaling-induced Smad3 nuclear accumulation induces acetylcholinesterase transcription in apoptotic HeLa cells

Recently, acetylcholinesterase (AChE) has been studied as an important apoptosis regulator. We previously showed that cellular calcium mobilization upregulated AChE expression by modulating promoter activity and mRNA stability. In this study, we have identified a potential Smad3/4 binding element, TGCCAGACA, located within the -601 to -571 bp fragment of the AChE promoter, as an important calcium response motif. Smad2/3 and Smad4 were shown to bind this element. Overexpression of human Smad3 increased AChE transcription activity in a dose-dependent manner in HeLa cells, whereas dominant-negative Smad3 blocked this activation. Upon A23187 and thapsigargin treatment, nuclear Smad3 accumulation was observed, an effect that was blocked by the intracellular Ca(2+) chelator BAPTA-AM. Calcium-induced AChE transcriptional activation was significantly blocked when the nuclear localization signal of Smad3 was destroyed. Taken together, our data suggest Smad3 can regulate AChE transcriptional activation following calcium-induced nuclear accumulation.

Genome wide ChIP-chip analyses reveal important roles for CTCF in Drosophila genome organization

Insulators or chromatin boundary elements are defined by their ability to block transcriptional activation by an enhancer and to prevent the spread of active or silenced chromatin. Recent studies have increasingly suggested that insulator proteins play a role in large-scale genome organization. To better understand insulator function on the global scale, we conducted a genome-wide analysis of the binding sites for the insulator protein CTCF in Drosophila by Chromatin Immunoprecipitation (ChIP) followed by a tiling-array analysis. The analysis revealed CTCF binding to many known domain boundaries within the Abd-B gene of the BX-C including previously characterized Fab-8 and MCP insulators, and the Fab-6 region. Based on this finding, we characterized the Fab-6 insulator element. In genome-wide analysis, we found that dCTCF-binding sites are often situated between closely positioned gene promoters, consistent with the role of CTCF as an insulator protein. Importantly, CTCF tends to bind gene promoters just upstream of transcription start sites, in contrast to the predicted binding sites of the insulator protein Su(Hw). These findings suggest that CTCF plays more active roles in regulating gene activity and it functions differently from other insulator proteins in organizing the Drosophila genome.

The CTCF insulator protein is posttranslationally modified by SUMO

The CTCF protein is a highly conserved zinc finger protein that is implicated in many aspects of gene regulation and nuclear organization. Its functions include the ability to act as a repressor of genes, including the c-myc oncogene. In this paper, we show that the CTCF protein can be posttranslationally modified by the small ubiquitin-like protein SUMO. CTCF is SUMOylated both in vivo and in vitro, and we identify two major sites of SUMOylation in the protein. The posttranslational modification of CTCF by the SUMO proteins does not affect its ability to bind to DNA in vitro. SUMOylation of CTCF contributes to the repressive function of CTCF on the c-myc P2 promoter. We also found that CTCF and the repressive Polycomb protein, Pc2, are colocalized to nuclear Polycomb bodies. The Pc2 protein may act as a SUMO E3 ligase for CTCF, strongly enhancing its modification by SUMO 2 and 3. These studies expand the repertoire of posttranslational modifications of CTCF and suggest roles for such modifications in its regulation of epigenetic states.

TGF-β1/SMAD signaling induces astrocyte fate commitmentin vitro: Implications for radial glia development

Radial glial (RG) cells are specialized type of cell, which functions as neuronal precursors and scaffolding guides to migrating neurons during cerebral cortex development. After neurogenesis and migration are completed, most of RG cells transform into astrocytes. Mechanism and molecules involved in this process are not completely elucidated. We previously demonstrated that neurons activate the promoter of the astrocyte maturation marker GFAP in astrocytes by secretion of transforming growth factor beta 1 (TGF-beta1) in vitro. Here, we studied the role of neurons and TGF-beta1 pathway in RG differentiation. To address this question, we employed cortical progenitor cultures enriched in GLAST/nestin double-labeled cells, markers of RG cells. TGF-beta1 and conditioned medium derived from neuron-astrocyte cocultures (CM) decreased the number of cells expressing the precursor marker nestin and increased that expressing GFAP in cortical progenitor cultures. These events were impaired by addition of neutralizing antibodies against TGF-beta1. Increase in the number of GFAP positive cells was associated with Smads 2/3 nuclear translocation, a hallmark of TGF-beta1 pathway activation. PCR-assays revealed a decrease in the levels of mRNA for the RG marker, BLBP (brain lipid binding protein), due to TGF-beta1 and CM treatment. We further identified TGF-beta1 receptor in cortical progenitor cultures suggesting that these cells might be target for TGF-beta1 during development. Our work provides strong evidence that TGF-beta1 might be a novel factor involved in RG-astrocyte transformation and highlights the role of neuron-glia interaction in this process.

Identification of a tyrosine-phosphorylated CCCTC-binding nuclear factor in capacitated mouse spermatozoa

The molecular basis of mammalian sperm capacitation, either in vivo in the female reproductive tract, or in vitro, is poorly understood. It is well known that sperm capacitation is associated with an increase in tyrosine phosphorylation of a subset of proteins. We resolved the phosphoproteins in the cell lysate of mouse sperm after capacitation by 2-DE. One tyrosine-phosphorylated 130-kDa spot was trypsin-digested, and six oligopeptide sequences were established from the MS data. These were confirmed in a CCCTC-binding nuclear factor (CTCF), a widely expressed and highly conserved protein. Further, both an anti-phosphotyrosine antibody and an anti-CTCF antibody showed immunoreactivity to a 130-kDa component in the immunoprecipitates obtained after incubation of the cell lysate from the capacitated sperm using another anti-CTCF antibody. The data support the presence of a tyrosine-phosphorylated CTCF in the capacitated sperm. Immunolocalization of the CTCF revealed fluorescent staining in the acrosome region in both capacitated and incapacitated sperm. The electrophoretic mobility shift assay, using a CTCF target sequence 5'-GGCGGCGCCGCTAGGGGTCTCTCT-3' found in the promoter of the amyloid beta-protein precursor, manifested that, relative to CTCF in the incapacitated sperm, the tyrosine-phosphorylated protein in the capacitated sperm had stronger affinity to the CTCF target sequence.

Altered subcellular location of phosphorylated Smads in Alzheimer's disease

A number of growth factors and cytokines, such as transforming growth factor beta 1 (TGF-beta1), is elevated in Alzheimer's disease (AD), giving rise to activated intracellular mitogenic signaling cascades. Activated mitogenic signaling involving the mitogen-activated protein kinases (MAPKs) and other protein kinases might alter the phosphorylation states of structural proteins such as tau, resulting in hyperphosphorylated deposits. Many intracellular signaling proteins are potential targets of misregulated phosphorylation and dephosphorylation. Recently, a crosstalk between MAPKs and Smad proteins, both involved in mediating TGF-beta1 signaling, has been reported. Although TGF-beta1 has previously been shown to be involved in the pathogenesis of AD, the role of Smad proteins has not been investigated. In this study we thus analysed the subcellular distribution of phosphorylated Smad2 and Smad3 in the hippocampus of both normal and AD brains. Here we report on strong nuclear detection of phosphorylated Smad2 and Smad3 in neurons of control brains. In AD brains these phosphorylated proteins were additionally found in cytoplasmic granules in hippocampal neurons, within amyloid plaques and attached to neurofibrillary tangles. Our data suggest a critical role of Smad proteins in the pathogenesis of AD.

Ectopic expression of phospho-Smad2 in Alzheimer's disease: Uncoupling of the transforming growth factor-β pathway?

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine, has been widely suggested to play a role in the pathogenesis of Alzheimer's disease. Supporting this, levels of TGF-beta are elevated in the cerebrospinal fluid, sera, and brain of patients with Alzheimer's disease. Since TGF-beta is neuroprotective, whereas Alzheimer's disease is typified by neurodegeneration, we speculated that defects in TGF-beta signaling might abrogate its neuroprotective properties. Consistently with an increase in TGF-beta in Alzheimer's disease, we found significant increases in phospho-Smad2, a major downstream signaling molecule of TGF-beta, in hippocampal neurons of Alzheimer's disease compared with age-matched control patients. However, in contrast to an expected nuclear localization, phosphorylated Smad2 in Alzheimer's disease was predominantly, and ectopically, found in the neuronal cytoplasm, specifically colocalized with neurofibrillary tangles and granulovacuolar degeneration. Given that a nuclear localization is required to regulate the transcription of TGF-beta target genes to afford neuroprotection, the ectopic localization of phosphorylated Smad2 suggests a defect in the Smad-mediated signaling pathway of TGF-beta in Alzheimer's disease and consequent loss of neuroprotective function.

A cross-species analysis of the rodent uterotrophic program: elucidation of conserved responses and targets of estrogen signaling

Physiological, morphological, and transcriptional alterations elicited by ethynyl estradiol in the uteri of Sprague-Dawley rats and C57BL/6 mice were assessed using comparable study designs, microarray platforms, and analysis methods to identify conserved estrogen signaling networks. Comparative analysis identified 153 orthologous gene pairs that were positively correlated, suggesting conserved transcriptional targets important in uterine proliferation. Functional annotation for these responses were associated with angiogenesis, water and solute transport, cell cycle control, redox control, DNA replication, protein synthesis and transport, xenobiotic metabolism, cell-cell communication, energetics, and cholesterol and fatty acid regulation. The identification of conserved temporal expression patterns of these orthologs provides experimental support for the transfer of functional annotation from mouse orthologs to 44 previously unannotated rat expressed sequence tags based on their homology and co-expression patterns. The identification of comparable temporal phenotypic responses linked to related gene expression profiles demonstrates the ability of systematic comparative genomic assessments to elucidate important conserved mechanisms in rodent estrogen signaling during uterine proliferation.

Emerging roles for TGF-beta1 in nervous system development

Transforming growth factor betas (TGF-betas) are known as multifunctional growth factors, which participate in the regulation of key events of development, disease and tissue repair. In central nervous system (CNS), TGF-beta1 has been widely recognized as an injury-related cytokine, specially associated with astrocyte scar formation in response to brain injury. TGF-betas family is represented by three isoforms: TGF-beta1, -beta 2 and -beta 3, all produced by both glial and neuronal cells. They are involved in essential tissue functions, including cell-cycle control, regulation of early development and differentiation, neuron survival and astrocyte differentiation. TGF-beta signaling is mediated mainly by two serine threonine kinase receptors, TGFRI and TGFRII, which activate Smad 2/3 and Smad 4 transcription factors. Phosphorylation and activation of these proteins is followed by formation of Smad 2/3-4 complex, which translocates to the nucleus regulating transcriptional responses to TGF-beta. Very few data are available concerning the intracellular pathway required for the effect of TGF-beta in brain cells. Recently, emerging data on TGF-beta1 and its signaling molecules have been suggesting that besides its role in brain injury, TGF-beta1 might be a crucial regulator of CNS development. In this review, we will focus on TGF-betas members, specially TGF-beta1, in neuron and astrocyte development. We will discuss some advances concerning the emerging scenario of TGF-beta1 and its signaling pathways as putative modulators of astrocyte biology and their implications as a novel mediator of cellular interactions in the CNS.

Regulation of the transcription factor, CTCF, by phosphorylation with protein kinase CK2

CTCF is a transcription factor involved in various aspects of gene regulation. We previously reported that CTCF function is modulated by protein kinase CK2. In this report we investigate further the role of CK2 in regulating the transcriptional properties of CTCF. We demonstrate that coexpression of CTCF with CK2 switches function of CTCF from repressor to activator. The non-phosphorylatable mutant increases repression by CTCF and potentiates the growth-suppressive ability of the protein, whereas the phospho-mimetic mutant behaves in the opposite fashion. Mutation of the individual serines reveals that Serine 612 is a critical residue in regulation of CTCF by CK2.

YB-1 and CTCF differentially regulate the 5-HTT polymorphic intron 2 enhancer which predisposes to a variety of neurological disorders

The serotonin transporter (5-HTT) gene contains a variable number tandem repeat (VNTR) domain within intron 2 that is often associated with a number of neurological conditions, including affective disorders. The implications of this polymorphism are not yet understood, however, we have previously demonstrated that the 5-HTT VNTR is a transcriptional regulatory domain, and the allelic variation supports differential reporter gene expression in vivo and in vitro. The aim of this study was to identify transcription factors responsible for the regulation of this VNTR. Using a yeast one-hybrid screen, we found the transcription factor Y box binding protein 1 (YB-1) interacts with the 5-HTT VNTR. Consistent with this, we demonstrate in a reporter gene assay that the polymorphic VNTR domains differentially respond to exogenous YB-1 and that YB-1 will bind to the VNTR in vitro in a sequence-specific manner. Interestingly, the transcription factor CCTC-binding factor (CTCF), previously shown to interact with YB-1, interferes with the ability of the VNTR to support YB-1-directed reporter gene expression. In addition, CTCF blocks the binding of YB-1 to its DNA recognition sequences in vitro, thus providing a possible mechanism of regulation of YB-1 activation of the VNTR by CTCF. Therefore, we have identified YB-1 and CTCF as transcription factors responsible, at least in part, for modulation of VNTR function as a transcriptional regulatory domain. Our data suggest a novel mechanism that explains, in part, the ability of the distinct VNTR copy numbers to support differential reporter gene expression based on YB-1 binding sites.

Cancer, inflammation and the AT1 and AT2 receptors

The critical role of inappropriate inflammation is becoming accepted in many diseases that affect man, including cardiovascular diseases, inflammatory and autoimmune disorders, neurodegenerative conditions, infection and cancer.

This review proposes that cancer up-regulates the angiotensin II type 1 (AT1) receptor through systemic oxidative stress and hypoxia mechanisms, thereby triggering chronic inflammatory processes to remodel surrounding tissue and subdue the immune system. Based on current literature and clinical studies on angiotensin receptor inhibitors, the paper concludes that blockade of the AT1 receptor in synergy with cancer vaccines and anti-inflammatory agents should offer a therapy to regress most, if not all, solid tumours.

With regard to cancer being a systemic disease, an examination of supporting evidence for a systemic role of AT1 in relationship to inflammation in disease and injury is presented as a logical progression. The evidence suggests that regulation of the mutually antagonistic angiotensin II receptors (AT1 and AT2) is an essential process in the management of inflammation and wound recovery, and that it is an imbalance in the expression of these receptors that leads to disease.

In consideration of cancer induced immune suppression, it is further postulated that the inflammation associated with bacterial and viral infections, is also an evolved means of immune suppression by these pathogens and that the damage caused, although incidental, leads to the symptoms of disease and, in some cases, death.

It is anticipated that manipulation of the angiotensin system with existing anti-hypertensive drugs could provide a new approach to the treatment of many of the diseases that afflict mankind.

Modelling neuroinflammatory phenotypes in vivo

Inflammation of the central nervous system is an important but poorly understood part of neurological disease. After acute brain injury or infection there is a complex inflammatory response that involves activation of microglia and astrocytes and increased production of cytokines, chemokines, acute phase proteins, and complement factors. Antibodies and T lymphocytes may be involved in the response as well. In neurodegenerative disease, where injury is more subtle but consistent, the inflammatory response is continuous. The purpose of this prolonged response is unclear, but it is likely that some of its components are beneficial and others are harmful. Animal models of neurological disease can be used to dissect the specific role of individual mediators of the inflammatory response and assess their potential benefit. To illustrate this approach, we discuss how mutant mice expressing different levels of the cytokine transforming growth factor beta-1 (TGF-beta1), a major modulator of inflammation, produce important neuroinflammatory phenotypes. We then demonstrate how crosses of TGF-beta1 mutant mice with mouse models of Alzheimer's disease (AD) produced important new information on the role of inflammation in AD and on the expression of different neuropathological phenotypes that characterize this disease.

Presence of a “CAGA box” in the APP gene unique to amyloid plaque‐forming species and absent in all APLP ‐1/2 genes: implications in Alzheimer's disease

Potentially toxic amyloid beta-peptide (Abeta) in Alzheimer's disease (AD) is generated from a family of Abeta-containing precursor proteins (APP), which is regulated via the 5'-untranslated region (5'-UTR) of its mRNA. We analyzed 5'-UTRs of the APP superfamily, including amyloid plaque-forming and non-amyloid plaque-forming species, and of prions (27 different DNA sequences). A "CAGA" sequence proximal to the "ATG" start codon was present in a location unique to APP genes of amyloid plaque-forming species and absent in all other genes surveyed. This CAGA box is immediately upstream of an interleukin-1-responsive element (acute box). In addition, the proximal CAGA box is predicted to appear on a stem-loop structure in both human and guinea pig APP mRNA. This stem-loop is part of a predicted bulge-loop that encompasses a known iron regulatory element (IRE). Electrophoretic mobility shift with segments of the APP 5'-UTR showed that a region with the proximal CAGA sequence binds nuclear proteins, and this UTR fragment is active in a reporter gene functional assay. Thus, the 5'-UTR in the human APP but not those of APP-like proteins contains a specific region that may participate in APP regulation and may determine a more general model for amyloid generation as seen in AD. The 5'-UTR of human APP contains several interesting control elements, such as an acute box element, a CAGA box, an IRE, and a transforming growth factor-beta-responsive element, that could control APP expression and provide suitable and specific drug targets for AD.

The many roles of the transcriptional regulator CTCF

The nuclear factor CTCF was first identified as one of the factors binding to the regulatory regions of the c-myc gene. Further study of this protein revealed roles in transcriptional repression, insulator function, and imprinting genetic information. Recent studies have provided new insight into the mechanism through which this factor acts at various levels of gene regulation.