Reelin Expression Research Articles

Sanhua Decoction, a Classic Herbal Prescription, Exerts Neuroprotection Through Regulating Phosphorylated Tau Level and Promoting Adult Endogenous Neurogenesis After Cerebral Ischemia/Reperfusion Injury.

Background: Ischemia stroke is the leading cause of death and long-term disability. Sanhua Decoction (SHD), a classic Chinese herbal prescription, has been used for ischemic stroke for about thousands of years. Here, we aim to investigate the neuroprotective effects of SHD on cerebral ischemia/reperfusion (CIR) injury rat models.Methods: The male Sprague-Dawley rats (body weight, 250–280 g; age, 7–8 weeks) were randomly divided into sham group, CIR group, and SHD group and were further divided into subgroups according to different time points at 6 h, 1, 3, 7, 14, 21, and 28 d, respectively. The SHD group received intragastric administration of SHD at 10 g kg−1 d−1. The focal CIR models were induced by middle cerebral artery occlusion according to Longa’s method, while sham group had the same operation without suture insertion. Neurological deficit score (NDS) was evaluated using the Longa’s scale. BrdU, doublecortin (DCX), and glial fibrillary acidic protein (GFAP) were used to label proliferation, migration, and differentiation of nerve cells before being observed by immunofluorescence. The expression of reelin, total tau (t-tau), and phosphorylated tau (p-tau) were evaluated by western blot and RT-qPCR.Results: SHD can significantly improve NDS at 1, 3, 7, and 14 d (p < 0.05), increase the number of BrdU positive and BrdU/DCX positive cells in subventricular zone at 3, 7, and 14 d (p < 0.05), upregulate BrdU/GFAP positive cells in the ischemic penumbra at 28 d after CIR (p < 0.05), and reduce p-tau level at 1, 3, 7, and 14 d (p < 0.05). There was no significant difference on reelin and t-tau level between three groups at each time points after CIR.Conclusions: SHD exerts neuroprotection probably by regulating p-tau level and promoting the proliferation, migration, and differentiation of endogenous neural stem cells, accompanying with neurobehavioral recovery.

An Overview of Extrinsic and Intrinsic Mechanisms Involved in Astrocyte Development in the Central Nervous System.

Over the past few decades, our knowledge about the function of the central nervous system (CNS) and astrocytes has improved, and research has confirmed the key roles that astrocytes play in the physiology and pathology of the CNS. Here, we reviewed the intrinsic and extrinsic mechanisms that regulate the development of astrocytes, which are generated from radial glial cells. These regulatory systems modulate various signaling pathways and transcription factors. In this review, four stages of astrocyte development-specification (patterning and switch), migration, proliferation, and maturation, are discussed. In astrocyte patterning, VA1-VA3 domains create the astrocyte subtypes by differential expression of Slit1 and Reelin in the spinal cord. In the brain, patterning creates several astrocyte subtypes by different organizing centers. At the switch step, the janus kinase-signal transducer and activator of transcription pathway governs the transition of neurogenesis to gliogenesis. Bone marrow protein and Notch pathways are also important players of the progliogenic switch. Intrinsic regulation is mediated by DNA methylation transferases, and polycomb group complexes can intrinsically affect the development of astrocytes. In the next stage, these cells proliferate and migrate to their final location. Astrocyte maturation is accomplished through the development of cellular processes, molecular markers, and functions.

Reelin in the Years: decline in the number of reelin immunoreactive neurons in layer II of the entorhinal cortex in aged monkeys with memory impairment

The glycoprotein reelin has been implicated in both memory-related synaptic plasticity and Alzheimer's disease pathogenesis. Aged rats with memory impairment display decreased reelin expression in layer II of the entorhinal cortex (EC) relative to memory-intact subjects, and here we tested whether this effect extends to the primate brain. Seven young adult (8–10 years) and 14 aged (27–38 years) rhesus monkeys (Macaca mulatta) were examined, including 7 old animals classified as impaired based on their scores from a delayed nonmatching-to-sample recognition memory test. Histological sections spanning the rostrocaudal extent of the intermediate and caudal divisions of EC were processed by immunohistochemistry and the total number of reelin-positive neurons in layer II was estimated using design-based stereological techniques. The main finding was that the number of reelin-expressing neurons in EC layer II is decreased selectively in aged monkeys with memory deficits relative to young adult and aged subjects with intact memory. The results add to evidence implicating EC-hippocampal integrity in neurocognitive aging, and they suggest that disrupted reelin signaling may be among the mechanisms that mediate the associated vulnerability of this circuitry in Alzheimer's disease.

Expression and localization of DAB1 and Reelin during normal human kidney development

AimTo explore the spatial and temporal expression patterns of DAB1 and Reelin in the developing and postnatal healthy human kidneys as potential determinants of kidney development.MethodsParaffin-embedded fetal kidney tissue between the 13/14th and 38th developmental weeks (dw) and postnatal tissue at 1.5 and 7 years were stained with DAB1 and Reelin antibodies by double immunofluorescence.ResultsDuring the fetal kidney development and postnatal period, DAB1 and Reelin showed specific spatial expression pattern and diverse fluorescence intensity. During the fetal period, DAB1 was strongly expressed in the distal convoluted tubules (DCT), with strong reactivity, and diversely in the proximal convoluted tubules (PCT) and glomeruli. In the postnatal period, DAB1 expression decreased. The strongest Reelin expression in early fetal stages was observed in the PCT. In the postnatal period, Reelin expression decreased dramatically in all observed structures. These two markers were colocalized during early developmental stages, mostly in PCT, DCT, and podocytes.ConclusionThe appearance of DAB1 and Reelin during fetal kidney development confirms their potential significant role in the formation of kidney structure or function. High DAB1 expression in the DCT implies its regulatory role in tubular formation or function maintenance during development. Reelin was highly expressed in human kidneys at early fetal stages, mostly in the PCT, while at later fetal stages and postnatal period its expression decreased.

Selective Inactivation of Reelin in Inhibitory Interneurons Leads to Subtle Changes in the Dentate Gyrus But Leaves Cortical Layering and Behavior Unaffected.

Reelin is an extracellular matrix protein, known for its dual role in neuronal migration during brain development and in synaptic plasticity at adult stages. During the perinatal phase, Reelin expression switches from Cajal-Retzius (CR) cells, its main source before birth, to inhibitory interneurons (IN), the main source of Reelin in the adult forebrain. IN-derived Reelin has been associated with schizophrenia and temporal lobe epilepsy; however, the functional role of Reelin from INs is presently unclear. In this study, we used conditional knockout mice, which lack Reelin expression specifically in inhibitory INs, leading to a substantial reduction in total Reelin expression in the neocortex and dentate gyrus. Our results show that IN-specific Reelin knockout mice exhibit normal neuronal layering and normal behavior, including spatial reference memory. Although INs are the major source of Reelin within the adult stem cell niche, Reelin from INs does not contribute substantially to normal adult neurogenesis. While a closer look at the dentate gyrus revealed some unexpected alterations at the cellular level, including an increase in the number of Reelin expressing CR cells, overall our data suggest that Reelin derived from INs is less critical for cortex development and function than Reelin expressed by CR cells.

Reduced Neuronal cAMP in the Nucleus Accumbens Damages Blood-Brain Barrier Integrity and Promotes Stress Vulnerability

BackgroundStudies have suggested that chronic social stress specifically downregulates endothelial tight junction protein expression in the nucleus accumbens (NAc), thus increasing blood-brain barrier (BBB) permeability and promoting depression-like behaviors. However, the molecular mechanism underlying the reduction in tight junction protein, particularly in the NAc, is largely uncharacterized. MethodsWe performed comparative metabolomic profiling of the nucleus accumbens, prefrontal cortex, and hippocampus of social defeat–stressed mice to identify the molecular events that mediate BBB breakdown. ResultsWe identified the levels of cyclic adenosine monophosphate (cAMP) that were specifically reduced in the NAc and positively correlated with the degree of social avoidance. Replenishing cAMP in the NAc was sufficient to improve BBB integrity and depression-like behaviors. We further found that cAMP levels were markedly decreased in neurons of the NAc, rather than in endothelial cells, astrocytes, or microglia. RNA-sequencing data showed that adenylate cyclase 5 (Adcy5), an enzyme responsible for the synthesis of cAMP from adenosine triphosphate (ATP), was predominantly expressed in the NAc; it also resided exclusively in neurons. Endogenous modulation of cAMP synthesis in neurons through the knockdown of Adcy5 in the NAc regulated the sensitivity to social stress. Moreover, deficient neuronal cAMP production in the NAc decreased the expression of reelin, while supplementary injection of exogenous reelin into the NAc promoted BBB integrity and ameliorated depression-like behaviors. ConclusionsChronic social stress diminished cAMP synthesis in neurons, thus damaging BBB integrity in the NAc and promoting stress vulnerability. These results characterize neuron-produced cAMP in the NAc as a biological mechanism of neurovascular pathology in social stress.

Disruption of Transient SERT Expression in Thalamic Glutamatergic Neurons Alters Trajectory of Postnatal Interneuron Development in the Mouse Cortex.

In mice, terminal differentiation of subpopulations of interneurons occurs in late postnatal stages, paralleling the emergence of the adult cortical architecture. Here, we investigated the effects of altered initial cortical architecture on later interneuron development. We identified that a class of somatostatin (SOM)-expressing GABAergic interneurons undergoes terminal differentiation between 2nd and 3rd postnatal week in the mouse somatosensory barrel cortex and upregulates Reelin expression during neurite outgrowth. Our previous work demonstrated that transient expression (E15-P10) of serotonin uptake transporter (SERT) in thalamocortical projection neurons regulates barrel elaboration during cortical map establishment. We show here that in thalamic neuron SERT knockout mice, these SOM-expressing interneurons develop at the right time, reach correct positions and express correct neurochemical markers, but only 70% of the neurons remain in the adult barrel cortex. Moreover, those neurons that remain display altered dendritic patterning. Our data indicate that a precise architecture at the cortical destination is not essential for specifying late-developing interneuron identities, their cortical deposition, and spatial organization, but dictates their number and dendritic structure ultimately integrated into the cortex. Our study illuminates how disruption of temporal-specific SERT function and related key regulators during cortical map establishment can alter interneuron development trajectory that persists to adult central nervous system.

Epileptiform activity induced by kainate application results in decreased Reelin expression and motility of differentiated granule cells

Epileptiform activity induced by kainate application results in decreased Reelin expression and motility of differentiated granule cells

Expression and Preparation of Recombinant Reelin and ADAMTS-3 Proteins.

Reelin is a large secreted protein that is essential for the brain development and function. Reelin is negatively regulated by the specific cleavage by a disintegrin and metalloproteinase with thrombospondin type 1 motifs 3 (ADAMTS-3) which is also secreted from neurons. It is likely that there are other proteases that can cleave Reelin. This chapter describes the protocol for expression and handling of recombinant Reelin and ADAMTS-3 proteins to facilitate investigation of these proteins.

Mesial Temporal Lobe Epilepsy: Role of Reelin Signalling Pathway

Abstract INTRODUCTION Granule cell dispersion (GCD) is pathognomonic of hippocampal sclerosis seen in mesial temporal lobe epilepsy (MTLE). Current animal studies associate GCD to deficiency of Reelin, an extracellular matrix protein. The present study evaluated complete Reelin signalling pathway in MTLE in human tissue hippocampus and anterior temporal lobe (ATL). ATL was included, as ATL resection along with amygdalo-hippocampectomy results in better disease control. METHODS Hematoxylin and Eosin (H&amp;E) staining was done to identify the MTLE. Gene expression profiles of Reelin and its receptors (very low density lipoprotein-VLDLR and Apolipoprotein E 2-ApoER2), its downstream molecule Disabled 1 (Dab1) and its upstream inhibitor tissue inhibitor of metalloproteinases-1 (TIMP-1) were compared in normal and epileptic human tissue. Quantitative real-time PCR was done to determine the gene expression in the hippocampus and ATL. Western blotting was done to quantify the protein expression. Ethical clearance was taken from the Institute Ethical committee. RESULTS Typical features of MTLE were seen histologically. Width of granule cell layer was found to be broadened than normal controls. The expression of Reelin was found to be in same order to that of control. But its expression has been reduced as compared to the other genes. Reactive increase in the expression of both receptors was found. In hippocampus increase was more for ApoER2 while in ATL VLDLR showed increased expression. Similarly increased expression of Dab1 was seen, more in the hippocampus. Significantly increased expression was found in TIMP-1. CONCLUSION Data suggests a causative role of Reelin deficiency in MTLE. The increase in TIMP-1 would inhibit the Reelin cleavage, leading to deficiency of active Reelin. Downstream components of the Reelin show reactive increase. Reelin deficiency in ATL validates the surgical significance of ATL resection. Establishing a causative role of Reelin in MTLE in human tissue might have significant therapeutic potential.

The effect of triiodothyronine on the hippocampal long-term potentiation in an animal model of the Alzheimer's disease: The role of BDNF and reelin

Converging evidence, propose a close relation between thyroid function and Alzheimer’s disease (AD). We have assessed the effect of subcutaneous and intrahippocampal administrations of triiodothyronine (T3) on the electrophysiological activity (hippocampal long-term potentiation (LTP)), the levels of thyroid hormones (THs) and TSH, the protein expression of BDNF and reelin as well as histological changes in the hippocampus of AD rats. Beta-amyloid (Aβ) plus ibotenic acid (Ibo) were injected intrahippocampally and rats were treated with T3 or saline. The hippocampal levels of THs and the protein expression are measured by ELISA kits and Western blotting method respectively. Results have been shown that T3 (S.C., and I. H), significantly reversed the amplitude and the slope impairment of the DG neurons, induced by Aβ. The hippocampal levels of THs, TSH and two protein expression were significantly decreased (p < 0.001) in AD animals and increased significantly in AD rats that have received T3 (S. C and I. H) (p < 0.01). Formation of amyloid plaques was declined in AD rats treated with T3. In conclusion, both S.C., and I.H. injections of T3 is effective in preventing the disruption of synaptic plasticity induced by Aβ. This positive effect of T3 may be mediated through a regulation of proteins expression and the hippocampal level of THs. The best effect was observed in I.H. microinjection of T3.

O-09 Some new links in the pathophysiological mechanisms of paranoid schizophrenia

The aim of the study is to elucidate new links in the pathophysiological mechanisms of paranoid schizophrenia. ERPs to the emotionally negative stimuli and to neutral stimuli (control) were recorded in 49 patients with paranoid schizophrenia with delusions and hallucinations and in 40 healthy subjects. Methylation of gene RELN in blood was also measured in the patients and control. ERPs to emotionally negative and thus more significant to the subjects stimuli evoked similar to that in the normal subjects activation of the occipital and inferior-temporal areas 200 ms after stimulus presentation (P200) in the right hemisphere, 300 ms after stimulus presentation (P300) in the left hemisphere and 400 ms after stimulus presentation (N400) again in the right hemisphere. In patients in the responses to the significant stimuli in prefrontal and frontal areas ERPs of all components revealed the increase of the latency and the amplitude while in central and temporal areas both these parameters were decreased. Methylation of gene RELN in patients appeared to be significantly reduced in comparison with the norm. Incongruent for the excitation as well as for the inhibition processes revealed in ERPs components in the patients could be caused by epigenetic pathology of the gene RELN, its demethylation being connected with aberrant expression of the protein reelin both in the blood and in the brain. This pathology may underlie abnormal pruning of the patients in frontal areas during the puberty and in the later life possibly resulting in the disturbance of the balance between excitation and inhibition processes.

The Neuroprotective Effect of miR-181a After Oxygen-Glucose Deprivation/Reperfusion and the Associated Mechanism.

The level of miR-181a decreases rapidly in N2a cells following oxygen-glucose deprivation/reperfusion, but its role in this process is unclear. Reelin, a regulator of neuronal migration and synaptogenesis, is a predicted target of miR-181a. We hypothesized that miR-181a reduces neuronal apoptosis and protects neurons by targeting reelin. Second mitochondria-derived activator of caspases (Smac) is a protein located in mitochondria that regulates apoptosis. The pro-apoptotic effect of Smac is achieved by reversing the effects of apoptosis-inhibiting proteins (IAPs), particularly X-linked inhibitor of apoptosis (XIAP). We also evaluated the effect of miR-181a on the Smac/IAP signaling pathway after oxygen-glucose deprivation and reperfusion in N2a cells. The miR-181a level, apoptosis rate, and the levels of reelin mRNA and protein, Smac, and XIAP were assessed in N2a cells subjected to oxygen-glucose deprivation for 4h and reperfusion for 0, 4, 12, or 24h with/without an miR-181a mimic, or mismatched control. Direct targeting of reelin by miR-181a was assessed in vitro by dual luciferase assay and immunoblotting. Pre-treatment with miR-181a mimicked the increase in the miR-181a level in N2a cells after oxygen-glucose deprivation/reperfusion, resulting in a significant decrease in the apoptosis rate. Changes in the miR-181a level in N2a cells were inversely correlated with reelin protein expression. Direct targeting of the reelin 3' untranslated region by miR-181a was verified by dual luciferase assay, which showed that miR-181a significantly inhibited luciferase activity. The Smac level was significantly lower in the miR-181a mimics than the normal control and mimics-cont groups (P < 0.01), whereas the level of XIAP was increased slightly. These findings suggest that miR-181a protects neurons from apoptosis by inhibiting reelin expression and regulating the Smac/IAP signaling pathway after oxygen-glucose deprivation/reperfusion injury.

Reelin Signaling in Vascular Endothelial Cell Biology

IntroductionEstablishment of the coronary circulation is a critical step in heart development. Formation of functional coronary vessels is required for the heart to undergo successful compaction of the ventricular myocardium. Oxygen and nutrients are delivered to the contractile myocardium through the coronary vasculature. Molecular signaling pathways that control formation of the coronary vessels are being identified. Immunofluorescent studies from our lab indicate that the Reelin extracellular matrix glycoprotein is expressed within the vascular endothelial cells of developing and mature coronary vessels of the mouse heart. The Reelin signaling pathway is known to contribute to brain and lymphatic system development by influencing neuronal and endothelial cell behaviors such as adhesion and migration. However, its role in coronary vascular development is as yet unidentified.Study ObjectiveThe goal of this study was to elucidate the potential roles of Reelin in formation of the coronary vasculature by identifying how it regulates vascular endothelial cell behaviors. We hypothesized that Reelin signaling regulates establishment of coronary vessel integrity during cardiogenesis by influencing vascular endothelial cell adhesion as well as cell membrane permeability and resistance.MethodsWe utilized the primary human dermal microvascular endothelial cell line (HDMEC) as an in vitro system to examine contributions of Reelin to vascular endothelial cell behavior. A small interfering RNA‐mediated approach was used to silence the endogenous RELN gene in HDMECs and reduce Reelin protein expression. Transfected HDMECs were subjected to cell‐based assays to assess changes in vascular endothelial cell behavior in response to RELN silencing. We assessed vascular endothelial cell adhesion on extracellular matrices that are required during coronary vessel development. Vessel integrity was examined by assaying endothelial cell membrane permeability and resistance in RELN‐silenced cells. Also, we examined the effect of Reelin expression on cell viability.ResultsRELN‐silenced HDMECs exhibited a &gt;90% reduction in Reelin expression in comparison to non‐targeting, negative control HDMECs. This significant Reelin reduction altered vascular endothelial cell adhesion to certain extracellular matrices. These RELN‐silenced HDMECs exhibited a significant decrease in baseline cell membrane permeability and concomitant changes in cell membrane resistance. Furthermore, we observed changes in cell morphology in RELN‐silenced cells versus control cells. Preliminary data suggests that loss of RELN expression affects vascular endothelial cell morphology and expression of components within the Reelin signaling pathway.ConclusionsBased on this evidence, we conclude that Reelin influences adhesion, morphology, membrane permeability and membrane resistance of vascular endothelial cells in order to regulate vessel wall integrity. These findings may provide key evidence as to how Reelin expression in nascent vascular endothelial cells impacts formation of the coronary vessels during mammalian cardiovascular development.Support or Funding InformationAHA 17AIREA3360773 and PCOM Center for Chronic Disorders of AgingThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Prenatal and early life diesel exhaust exposure disrupts cortical lamina organization: Evidence for a reelin-related pathogenic pathway induced by interleukin-6

Several epidemiological studies have shown associations between developmental exposure to traffic-related air pollution and increased risk for autism spectrum disorders (ASD), a spectrum of neurodevelopmental disorders with increasing prevalence rate in the United States. Though animal studies have provided support for these associations, little is known regarding possible underlying mechanisms. In a previous study we found that exposure of C57BL/6J mice of both sexes to environmentally relevant levels (250–300 µg/m3) of diesel exhaust (DE) from embryonic day 0 to postnatal day 21 (E0 to PND21) caused significant changes in all three characteristic behavioral domains of ASD in the offspring. In the present study we investigated a potential mechanistic pathway that may be of relevance for ASD-like changes associated with developmental DE exposure. Using the same DE exposure protocol (250–300 µg/m3 DE from E0 to PND21) several molecular markers were examined in the brains of male and female mice at PND3, 21, and 60. Exposure to DE as above increased levels of interleukin-6 (IL-6) in placenta and in neonatal brain. The JAK2/STAT3 pathway, a target for IL-6, was activated by STAT3 phosphorylation, and the expression of DNA methyltransferase 1 (DNMT1), a STAT3 target gene, was increased in DE-exposed neonatal brain. DNMT1 has been reported to down-regulate expression of reelin (RELN), an extracellular matrix glycoprotein important in regulating the processes of neuronal migration. RELN is considered an important modulator for ASD, since there are several polymorphisms in this gene linked to the disease, and since lower levels of RELN have been reported in brains of ASD patients. We observed decreased RELN expression in brains of the DE-exposed mice at PND3. Since disorganized patches in the prefrontal cortex have been reported in ASD patients and disrupted cortical organization has been found in RELN-deficient mice, we also assessed cortical organization, by labeling cells expressing the lamina-specific-markers RELN and calretinin. In DE-exposed mice we found increased cell density in deeper cortex (lamina layers VI–IV) for cells expressing either RELN or calretinin. These findings demonstrate that developmental DE exposure is associated with subtle disorganization of the cerebral cortex at PND60, and suggest a pathway involving IL-6, STAT3, and DNMT1 leading to downregulation of RELN expression that could be contributing to this long-lasting disruption in cortical laminar organization.

Prenatal exposure and fetal programming of schizophrenia

Schizophrenia (SCZ) is a neurodevelopmental disorder, which results to cognitive dysfunction and memory decline. Maternal undernutrition during fetal development alters epigenomic programming, and this might result to SCZ in offspring later in life because of the disruption of fetal brain development and synaptogenesis. Maternal stress, exposure to teratogens and neurotoxic agent, hypoxia, and viral infection alters fetal neurodevelopmental mechanisms because of an increase in inflammatory proteins. Interleukin 8 and tumor necrosis factor released due to stress and infection increase the risk of offspring developing SCZ later in life. Having infections linked to Toxoplasma gondii, Chlamydia, and some pathogens seropositivity during pregnancy or the period preceding childbirth are high-risk factors for offspring to develop SCZ later in life. This review was conducted by extracting papers using key terms indicating Schizophrenia, fetal programming of neurodevelopmental disorders, maternal undernutrition, maternal immune activation, and genome-wide studies through PubMed, Science Direct, PsychINFO, Medline, Web of Science, and Google Scholar. Maternal Stress was found to induce hypermethylation resulting to poor expression of reelin, which causes a reduction in GABAergic neurons in animal models. In vivo animal experimentation indicated that poor maternal care, unfavorable environmental factors, and conditions produce aberrant deoxyribonucleic acid methylation patterns at various gene loci in the medial prefrontal cortex of the brain, thus altering and modifying the network of genes involved in mental activities. However, the epigenomic mechanisms behind the fetal programming of SCZ have not been fully understood; more facts could be unraveled in the future.

TGF-β1 promotes cell migration in hepatocellular carcinoma by suppressing reelin expression

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is a leading cause of worldwide cancer mortality. Intrahepatic dissemination and extrahepatic metastasis are key factors in malignant growth of HCC. Reducing HCC-associated metastasis is critically dependent on uncovering molecular signaling pathways that promote HCC metastasis. In this study, we explored the effect of TGF-β1 and RELN on cell migration, and the relationship between TGF-β1 and RELN in HCC cells. The data presented that TGF-β1 and RELN showed an opposite expression pattern, and either increased expression of TGF-β1 or decreased expression of RELN increased HCC cell migration ability. We also found TGF-β1 enhanced cell migration ability was through repressing RELN expression, as overexpression of RELN impaired TGF-β1 enhanced cell migration. Our work revealed the relationship between TGF-β1 and RELN and uncovered the important role of RELN in suppressing cell migration in HCC cells.

Ataxia telangiectasia alters the ApoB and reelin pathway.

Autosomal recessive ataxia telangiectasia (A-T) is characterized by radiosensitivity, immunodeficiency, and cerebellar neurodegeneration. A-T is caused by inactivating mutations in the ataxia telangiectasiamutated (ATM) gene, a serine-threonine protein kinase involved in DNA damage response and excitatory neurotransmission. The selective vulnerability of cerebellar Purkinje neurons (PN) to A-T is not well understood. Employing global proteomic profiling of cerebrospinal fluid from patients at ages around 15years, we detected reduced calbindin, reelin, cerebellin-1, cerebellin-3, protocadherin fat 2, sempahorin 7A, and increased apolipoprotein B and J peptides. Bioinformatic enrichment was observed for pathways of lipoproteins, endocytosis, extracellular matrix receptor interaction, peptidase activity, adhesion, calcium binding, and complement immunity. This seemed important since secretion of reelin from glutamatergic afferent axons is crucial for PN lipoprotein receptor endocytosis and lipid signaling. Reelin expression is downregulated by irradiation and reelin/ApoB mutations are known causes of ataxia. Validation efforts in 2-month-old Atm-/- mice before onset of motor deficits confirmed cerebellar transcript reductions for reelin receptors Apoer2/Vldlr with increases for their ligands Apoe/Apoh and cholesterol 24-hydroxylase Cyp46a1. Concomitant dysregulations were found for Vglut2/Sema7a as climbing fiber markers, glutamate receptors like Grin2b, and calcium homeostasis factors (Atp2b2, Calb1, Itpr1), while factors involved in DNA damage, oxidative stress, neuroinflammation, and cell adhesion were normal at this stage. Quantitative immunoblots confirmed ApoB and ApoJ increases and VLDLR reduction in cerebellar tissue at the age of 2months. These findings show that ApoB excess and reelin signaling deficits reflect the neurodegeneration in A-T in a sensitive and specific way. As extracellular factors, apolipoproteins and their cargo such as vitamin E may be useful for neuroprotective interventions.

Distal Dendritic Enrichment of HCN1 Channels in Hippocampal CA1 Is Promoted by Estrogen, but Does Not Require Reelin.

HCN1 compartmentalization in CA1 pyramidal cells, essential for hippocampal information processing, is believed to be controlled by the extracellular matrix protein Reelin. Expression of Reelin, in turn, is stimulated by 17β-estradiol (E2). In this study, we therefore tested whether E2 regulates the compartmentalization of HCN1 in CA1 via Reelin. In organotypic entorhino-hippocampal cultures, we found that E2 promotes HCN1 distal dendritic enrichment via the G protein–coupled estrogen receptor GPER1, but apparently independent of Reelin, because GST-RAP, known to reduce Reelin signaling, did not prevent E2-induced HCN1 enrichment in distal CA1. We therefore re-examined the role of Reelin for the regulation of HCN1 compartmentalization and could not detect effects of reduced Reelin signaling on HCN1 distribution in CA1, either in the (developmental) slice culture model or in tamoxifen-inducible conditional reelin knockout mice during adulthood. We conclude that for HCN1 channel compartmentalization in CA1 pyramidal cells, Reelin is not as essential as previously proposed, and E2 effects on HCN1 distribution in CA1 are mediated by mechanisms that do not involve Reelin. Because HCN1 localization was not altered at different phases of the estrous cycle, gonadally derived estradiol is unlikely to regulate HCN1 channel compartmentalization, while the pattern of immunoreactivity of aromatase, the final enzyme of estradiol synthesis, argues for a role of local hippocampal E2 synthesis.

Maternal Deprivation Enhances Contextual Fear Memory via Epigenetically Programming Second-Hit Stress-Induced Reelin Expression in Adult Rats.

BackgroundEarly-life stress increases the risk for posttraumatic stress disorder. However, the epigenetic mechanism of early-life stress-induced susceptibility to posttraumatic stress disorder in adulthood remains unclear.MethodsRat pups were exposed to maternal deprivation during postnatal days 1 to 14 for 3 hours daily and treated with the DNA methyltransferase inhibitor zebularine, L-methionine, or vehicle 7 days before contextual fear conditioning, which was used as a second stress and to mimic the reexperiencing symptom of posttraumatic stress disorder in adulthood. Long-term potentiation, dendritic spine density, DNA methyltransferase mRNA, Reelin gene methylation, and Reelin protein expression in the hippocampal CA1 were measured.ResultsMaternal deprivation enhanced contextual fear memory in adulthood. Meanwhile, maternal deprivation decreased DNA methyltransferase mRNA and Reelin gene methylation in the hippocampal CA1 on postnatal days 22 and 90. Reelin protein expression was increased in the hippocampal CA1 following contextual fear conditioning in adulthood. Furthermore, compared with rats that experienced maternal deprivation alone, rats also exposed to contextual fear conditioning showed an enhanced induction of hippocampal long-term potentiation and increased dendritic spine density in the hippocampal CA1 following contextual fear conditioning in adulthood. Zebularine pretreatment led to an enhancement of contextual fear memory, hypomethylation of the Reelin gene, and increased Reelin protein expression in adult rats, while L-methionine had the opposite effects.ConclusionsMaternal deprivation can epigenetically program second-hit stress-induced Reelin expression and enhance the susceptibility to contextual fear memory in adulthood. These findings provide a new framework for understanding the cumulative stress hypothesis.