Dp71 Point Mutations Induce Protein Aggregation, Loss of Nuclear Lamina Integrity and Impaired Braf35 and Ibraf Function in Neuronal Cells.

Dystrophin Dp71 is the most abundant product of the Duchenne muscular dystrophy gene in the nervous system, and mutations impairing its function have been associated with the neurodevelopmental symptoms present in a third of DMD patients. Dp71 is required for the clustering of neurotransmitter receptors and the neuronal differentiation of cultured cells; nonetheless, its precise role in neuronal cells remains to be poorly understood. In this study, we analyzed the effect of two pathogenic DMD gene point mutations on the Dp71 function in neurons. We engineered C272Y and E299del mutations to express GFP-tagged Dp71 protein variants in N1E-115 and SH-SY5Y neuronal cells. Unexpectedly, the ectopic expression of Dp71 mutants resulted in protein aggregation, which may be mechanistically caused by the effect of the mutations on Dp71 structure, as predicted by protein modeling and molecular dynamics simulations. Interestingly, Dp71 mutant variants acquired a dominant negative function that, in turn, dramatically impaired the distribution of different Dp71 protein partners, including ß-dystroglycan, nuclear lamins A/C and B1, the high-mobility group (HMG)-containing protein (BRAF35) and the BRAF35-family-member inhibitor of BRAF35 (iBRAF). Further analysis of Dp71 mutants provided evidence showing a role for Dp71 in modulating both heterochromatin marker H3K9me2 organization and the neuronal genes' expression, via its interaction with iBRAF and BRAF5.

Effects of Physical Rehabilitation in Patients with Spinocerebellar Ataxia Type 7.

Today, neurorehabilitation has become in a widely used therapeutic approach in spinocerebellar ataxias; however, there are scarce powerful clinical studies supporting this notion, and these studies require extension to other specific SCA subtypes in order to be able to form conclusions concerning its beneficial effects. Therefore, in this study, we perform for the first time a case-control pilot randomized, single-blinded, cross-sectional, and observational study to evaluate the effects of physical neurorehabilitation on the clinical and biochemical features of patients with spinocerebellar ataxia type 7 (SCA7) in 18 patients diagnosed with SCA7. In agreement with the exercise regimen, the participants were assigned to groups as follows: (a) the intensive training group, (b) the moderate training group, and (c) the non-training group (control group).We found that both moderate and intensive training groups showed a reduction in SARA scores but not INAS scores, compared with the control group (p < 0.05). Furthermore, trained patients exhibited improvement in the SARA sub-scores in stance, gait, dysarthria, dysmetria, and tremor, as compared with the control group (p < 0.05). No significant improvements were found in daily living activities, as revealed by Barthel and Lawton scales (p > 0.05). Patients under physical training exhibited significantly decreased levels in lipid-damage biomarkers and malondialdehyde, as well as a significant increase in the activity of the antioxidant enzyme PON-1, compared with the control group (p < 0.05). Physical exercise improved some cerebellar characteristics and the oxidative state of patients with SCA7, which suggest a beneficial effect on the general health condition of patients.

Oxidative Stress in Spinocerebellar Ataxia Type 7 Is Associated with Disease Severity.

Spinocerebellar ataxia type 7 is a neurodegenerative inherited disease caused by a CAG expansion in the coding region of the ATXN7 gene, which results in the synthesis of polyglutamine-containing ataxin-7. Expression of mutant ataxin-7 disturbs different cell processes, including transcriptional regulation, protein conformation and clearance, autophagy, and glutamate transport; however, mechanisms underlying neurodegeneration in SCA7 are still unknown. Implication of oxidative stress in the pathogenesis of various neurodegenerative diseases, including polyglutamine disorders, has recently emerged. We perform a cross-sectional study to determine for the first time pheripheral levels of different oxidative stress markers in 29 SCA7 patients and 28 age- and sex-matched healthy subjects. Patients with SCA7 exhibit oxidative damage to lipids (high levels of lipid hydroperoxides and malondialdehyde) and proteins (elevated levels of advanced oxidation protein products and protein carbonyls). Furthermore, SCA7 patients showed enhanced activity of various anti-oxidant enzymes (glutathione reductase, glutathione peroxidase, and paraoxonase) as well as increased total anti-oxidant capacity, which suggest that activation of the antioxidant defense system might occur to counteract oxidant damage. Strikingly, we found positive correlation between some altered oxidative stress markers and disease severity, as determined by different clinical scales, with early-onset patients showing a more severe disturbance of the redox system than adult-onset patients. In summay, our results suggest that oxidative stress might contribute to SCA7 pathogenesis. Furthermore, oxidative stress biomarkers that were found relevant to SCA7 in this study could be useful to follow disease progression and monitor therapeutic intervention.

A Complete Association of an intronic SNP rs6798742 with Origin of Spinocerebellar Ataxia Type 7-CAG Expansion Loci in the Indian and Mexican Population.

Spinocerebellar ataxia type 7 (SCA7) is a rare neurogenetic disorder caused by highly unstable CAG repeat expansion mutation in coding region of SCA7. We aimed to understand the effect of diverse ATXN7 cis-element in correlation with CAG expansion mutation of SCA7. We initially performed an analysis to identify the haplotype background of CAG expanded alleles using eight bi-allelic single nucleotide polymorphisms (SNPs) flanking an ATXN7-CAG expansion in 32 individuals from nine unrelated Indian SCA7 families and 88 healthy controls. Subsequent validation of the findings was performed in 89 ATXN7-CAG mutation carriers and in 119 unrelated healthy controls of Mexican ancestry. The haplotype analyses showed a shared haplotype background and C allele of SNP rs6798742 (approximately 6 kb from the 3'-end of CAG repeats) is in complete association with expanded, premutation, intermediate, and the majority of large normal (≥12) CAG allele. The C allele (ancestral/chimp allele) association was validated in SCA7 subjects and healthy controls from Mexico, suggesting its substantial association with CAG expanded and expansion-prone chromosomes. Analysis of rs6798742 and other neighboring functional SNPs within 6 kb in experimental datasets (Encyclopedia of DNA Elements; ENCODE) shows functional marks that could affect transcription as well as histone methylation. An allelic association of the CAG region to an intronic SNP in two different ethnic and geographical populations suggests a -cis factor-dependent mechanism in ATXN7 CAG-region expansion.

Dysferlin quantification in monocytes for rapid screening for dysferlinopathies.

INTRODUCTION: In this study, we determined normal levels of dysferlin expression in CD14+ monocytes by flow cytometry (FC) as a screening tool for dysferlinopathies. METHODS: Monocytes from 183 healthy individuals and 29 patients were immunolabeled, run on an FACScalibur flow cytometer, and analyzed by FlowJo software. RESULTS: The relative quantity of dysferlin was expressed as mean fluorescence intensity (MFI). Performance of this diagnostic test was assessed by calculating likelihood ratios at different MFI cut-off points, which allowed definition of 4 disease classification groups in a simplified algorithm. CONCLUSION: The MFI value may differentiate patients with dysferlinopathy from healthy individuals; it may be a useful marker for screening purposes. Muscle Nerve 54: 1064-1071, 2016.

Spinocerebellar ataxia type 7: a neurodegenerative disorder with peripheral neuropathy.

BACKGROUND: Autosomal dominant spinocerebellar ataxias (SCA) are a group of inherited neurodegenerative disorders that typically show peripheral neuropathy. SCA7 is one of the rarest forms of SCA (<1/100,000 individuals). However, the disease shows a prevalence of ∼800/100,000 inhabitants in certain regions of Mexico. This low global prevalence may explain, at least in part, the isolated anecdotal and limited clinical data regarding peripheral neuropathy in SCA7 patients. AIM: To assess sensory and motor peripheral nerve action potentials in an SCA7 patients group and in healthy volunteers, and subsequently correlate the electrophysiological findings with clinical and genetic features. MATERIALS AND METHODS: We enrolled in our study, 13 symptomatic SCA7 patients with a confirmed molecular and clinical diagnosis, and 19 healthy volunteers as the control group. Nerve conduction studies were carried out using standard electromyography recording methods. The sensory and motor latency, amplitude and conduction velocity were recorded in both experimental groups and analyzed using the Student's t-test. RESULTS: SCA7 patients showed a significant prolongation of sensory nerve conduction latencies, as well as a decrease in sensory amplitudes. Decreases in motor amplitudes and peroneal conduction velocity were also observed. Finally, we found an association between CAG repeats and the severity of cerebellar and non-cerebellar symptoms with electrophysiological signs of demyelinization. DISCUSSION: Our results reveal the existence of a critical sensorimotor peripheral neuropathy in SCA7 patients. Moreover, we show that using sensitive electrophysiological tools to evaluate nerve conduction can improve the diagnosis and design of therapeutic options based on pharmacological and rehabilitative strategies. CONCLUSION: These findings demonstrate that SCA7 is a disease that globally affects the peripheral nervous system.

Recessive spinocerebellar ataxia with paroxysmal cough attacks: a report of five cases.

Hereditary ataxias are a heterogeneous group of neurological diseases characterized by progressive cerebellar syndrome and numerous other features, which result in great diversity of ataxia subtypes. Despite the characterization of a number of both autosomal dominant and autosomal recessive ataxias, it is thought that a large group of these conditions remains to be identified. In this study, we report the characterization of five patients (three Mexicans and two Italians) who exhibit a peculiar form of recessive ataxia associated with coughing. The main clinical and neurophysiological features of these patients include cerebellar ataxia, paroxysmal cough, restless legs syndrome (RLS), choreic movements, atrophy of distal muscles, and oculomotor disorders. Brain magnetic resonance imaging (MRI) revealed cerebellar atrophy, while video polysomnography (VPSG) studies showed a severe pattern of breathing-related sleep disorder, including sleep apnea, snoring, and significant oxygen saturation in the absence of risk factors. All patients share clinical features in the peripheral nervous system, including reduction of amplitude and prolonged latency of sensory potentials in median and sural nerves. Altogether, clinical criteria as well as molecular genetic testing that was negative for different autosomal dominant and autosomal recessive ataxias suggest the presence of a new form of recessive ataxia. This ataxia, in which cerebellar signs are preceded by paroxysmal cough, affects not only the cerebellum and its fiber connections, but also the sensory peripheral nervous system and extracerebellar central pathways.

Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse behaviour.

Myotonic dystrophy type 1 is a complex multisystemic inherited disorder, which displays multiple debilitating neurological manifestations. Despite recent progress in the understanding of the molecular pathogenesis of myotonic dystrophy type 1 in skeletal muscle and heart, the pathways affected in the central nervous system are largely unknown. To address this question, we studied the only transgenic mouse line expressing CTG trinucleotide repeats in the central nervous system. These mice recreate molecular features of RNA toxicity, such as RNA foci accumulation and missplicing. They exhibit relevant behavioural and cognitive phenotypes, deficits in short-term synaptic plasticity, as well as changes in neurochemical levels. In the search for disease intermediates affected by disease mutation, a global proteomics approach revealed RAB3A upregulation and synapsin I hyperphosphorylation in the central nervous system of transgenic mice, transfected cells and post-mortem brains of patients with myotonic dystrophy type 1. These protein defects were associated with electrophysiological and behavioural deficits in mice and altered spontaneous neurosecretion in cell culture. Taking advantage of a relevant transgenic mouse of a complex human disease, we found a novel connection between physiological phenotypes and synaptic protein dysregulation, indicative of synaptic dysfunction in myotonic dystrophy type 1 brain pathology.

Development of a Polymeric Pharmacological Nanocarrier System as a Potential Therapy for Spinocerebellar Ataxia Type 7.

Spinocerebellar ataxia type 7 (SCA7) is an autosomal-dominant inherited disease characterized by progressive ataxia and retinal degeneration. SCA7 belongs to a group of neurodegenerative diseases caused by an expanded CAG repeat in the disease-causing gene, resulting in aberrant polyglutamine (polyQ) protein synthesis. PolyQ ataxin-7 is prone to aggregate in intracellular inclusions, perturbing cellular processes leading to neuronal death in specific regions of the central nervous system (CNS). Currently, there is no treatment for SCA7; however, a promising approach successfully applied to other polyQ diseases involves the clearance of polyQ protein aggregates through pharmacological activation of autophagy. Nonetheless, the blood-brain barrier (BBB) poses a challenge for delivering drugs to the CNS, limiting treatment effectiveness. This study aimed to develop a polymeric nanocarrier system to deliver therapeutic agents across the BBB into the CNS. We prepared poly(lactic-co-glycolic acid) nanoparticles (NPs) modified with Poloxamer188 and loaded with rapamycin to enable NPs to activate autophagy. We demonstrated that these rapamycin-loaded NPs were successfully taken up by neuronal and glial cells, demonstrating high biocompatibility without adverse effects. Remarkably, rapamycin-loaded NPs effectively cleared mutant ataxin-7 aggregates in a SCA7 glial cell model, highlighting their potential as a therapeutic approach to fight SCA7 and other polyQ diseases.

Myotonic dystrophy type 1-associated CTG repeats disturb the expression and subcellular distribution of microtubule-associated proteins MAP1A, MAP2, and MAP6/STOP in PC12 cells.

To study the effect of DM1-associated CTG repeats on neuronal function, we developed a PC12 cell-based model that constitutively expresses the DMPK gene 3'-untranslated region with 90 CTG repeats (CTG90 cells). As CTG90 cells exhibit impaired neurite outgrowth and as microtubule-associated proteins (MAPs) are crucial for microtubule stability, we analyzed whether MAPs are a target of CTG repeats. NGF induces mRNA expression of Map2, Map1a and Map6 in control cells (PC12 cells transfected with the empty vector), but this induction is abolished for Map2 and Map1a in CTG90 cells. MAP2 and MAP6/STOP proteins decrease in NGF-treated CTG90 cells, whereas MAP1A increases. Data suggest that CTG repeats might alter somehow the expression of MAPs, which appears to be related with CTG90 cell-deficient neurite outgrowth. Decreased MAP2 levels found in the hippocampus of a DM1 mouse model indicates that targeting of MAPs expression by CTG repeats might be relevant to DM1.

RNA Foci Formation in a Retinal Glial Model for Spinocerebellar Ataxia Type 7.

Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disorder characterized by cerebellar ataxia and retinopathy. SCA7 is caused by a CAG expansion in the ATXN7 gene, which results in an extended polyglutamine (polyQ) tract in the encoded protein, the ataxin-7. PolyQ expanded ataxin-7 elicits neurodegeneration in cerebellar Purkinje cells, however, its impact on the SCA7-associated retinopathy remains to be addressed. Since Müller glial cells play an essential role in retinal homeostasis, we generate an inducible model for SCA7, based on the glial Müller MIO-M1 cell line. The SCA7 pathogenesis has been explained by a protein gain-of-function mechanism, however, the contribution of the mutant RNA to the disease cannot be excluded. In this direction, we found nuclear and cytoplasmic foci containing mutant RNA accompanied by subtle alternative splicing defects in MIO-M1 cells. RNA foci were also observed in cells from different lineages, including peripheral mononuclear leukocytes derived from SCA7 patient, suggesting that this molecular mark could be used as a blood biomarker for SCA7. Collectively, our data showed that our glial cell model exhibits the molecular features of SCA7, which makes it a suitable model to study the RNA toxicity mechanisms, as well as to explore therapeutic strategies aiming to alleviate glial dysfunction.

Myotonic dystrophy RNA toxicity alters morphology, adhesion and migration of mouse and human astrocytes.

Brain dysfunction in myotonic dystrophy type 1 (DM1), the prototype of toxic RNA disorders, has been mainly attributed to neuronal RNA misprocessing, while little attention has been given to non-neuronal brain cells. Here, using a transgenic mouse model of DM1 that expresses mutant RNA in various brain cell types (neurons, astroglia, and oligodendroglia), we demonstrate that astrocytes exhibit impaired ramification and polarization in vivo and defects in adhesion, spreading, and migration. RNA-dependent toxicity and phenotypes are also found in human transfected glial cells. In line with the cell phenotypes, molecular analyses reveal extensive expression and accumulation of toxic RNA in astrocytes, which result in RNA spliceopathy that is more severe than in neurons. Astrocyte missplicing affects primarily transcripts that regulate cell adhesion, cytoskeleton, and morphogenesis, and it is confirmed in human brain tissue. Our findings demonstrate that DM1 impacts astrocyte cell biology, possibly compromising their support and regulation of synaptic function.

Transcriptome Analysis Reveals Altered Inflammatory Pathway in an Inducible Glial Cell Model of Myotonic Dystrophy Type 1.

Myotonic dystrophy type 1 (DM1), the most frequent inherited muscular dystrophy in adults, is caused by the CTG repeat expansion in the 3'UTR of the DMPK gene. Mutant DMPK RNA accumulates in nuclear foci altering diverse cellular functions including alternative splicing regulation. DM1 is a multisystemic condition, with debilitating central nervous system alterations. Although a defective neuroglia communication has been described as a contributor of the brain pathology in DM1, the specific cellular and molecular events potentially affected in glia cells have not been totally recognized. Thus, to study the effects of DM1 mutation on glial physiology, in this work, we have established an inducible DM1 model derived from the MIO-M1 cell line expressing 648 CUG repeats. This new model recreated the molecular hallmarks of DM1 elicited by a toxic RNA gain-of-function mechanism: accumulation of RNA foci colocalized with MBNL proteins and dysregulation of alternative splicing. By applying a microarray whole-transcriptome approach, we identified several gene changes associated with DM1 mutation in MIO-M1 cells, including the immune mediators CXCL10, CCL5, CXCL8, TNFAIP3, and TNFRSF9, as well as the microRNAs miR-222, miR-448, among others, as potential regulators. A gene ontology enrichment analyses revealed that inflammation and immune response emerged as major cellular deregulated processes in the MIO-M1 DM1 cells. Our findings indicate the involvement of an altered immune response in glia cells, opening new windows for the study of glia as potential contributor of the CNS symptoms in DM1.

Recombinant human ZP3-induced sperm acrosome reaction: evidence for the involvement of T- and L-type voltage-gated calcium channels.

For successful fertilization mammalian spermatozoa must undergo the acrosome reaction (AR), an exocytotic event that allows this cell to penetrate the outer layer of the oocyte, the zona pellucida (ZP). Four glycoproteins (ZP1-ZP4) compose the human ZP, being ZP3 the physiological inductor of the AR. This process requires changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) involving not fully understood mechanisms. Even in mouse sperm, the pharmacologically documented participation of voltage-gated Ca(2+) (Ca(V)) channels and store-operated channels (SOCs) in the ZP-induced AR is being debated. The situation in human sperm is even less clear due to the limited availability of human ZP. Here, we used recombinant human ZP3 (rhZP3) produced in baculovirus-infected Sf9 cells to investigate the involvement of Ca(V) channels in the human sperm AR. Our findings showed that Ni(2+) and mibefradil at concentrations that block T-type or Ca(V)3 channels, and nimodipine and diltiazem that block L-type or Ca(V)1 channels, significantly inhibited the rhZP3-initiated AR. On the other hand, the AR was insensitive to concentrations of omega-Agatoxin IVA, omega-Conotoxin GVIA and SNX-482 that block P/Q, N and R-type channels, respectively (Ca(V)2 channels). Our overall findings suggest that Ca(V)1 and Ca(V)3 channels participate in human sperm AR. Consistent with this, we detected in human sperm transcripts for the Ca(V)1 auxiliary subunits, alpha(2)delta, beta(1), beta(2) and beta(4), but not the neuronal specific isoforms beta(3) and gamma(2).

Chromatin Landscape During Skeletal Muscle Differentiation.

Cellular commitment and differentiation involve highly coordinated mechanisms by which tissue-specific genes are activated while others are repressed. These mechanisms rely on the activity of specific transcription factors, chromatin remodeling enzymes, and higher-order chromatin organization in order to modulate transcriptional regulation on multiple cellular contexts. Tissue-specific transcription factors are key mediators of cell fate specification with the ability to reprogram cell types into different lineages. A classic example of a master transcription factor is the muscle specific factor MyoD, which belongs to the family of myogenic regulatory factors (MRFs). MRFs regulate cell fate determination and terminal differentiation of the myogenic precursors in a multistep process that eventually culminate with formation of muscle fibers. This developmental progression involves the activation and proliferation of muscle stem cells, commitment, and cell cycle exit and fusion of mononucleated myoblast to generate myotubes and myofibers. Although the epigenetics of muscle regeneration has been extensively addressed and discussed over the recent years, the influence of higher-order chromatin organization in skeletal muscle regeneration is still a field of development. In this review, we will focus on the epigenetic mechanisms modulating muscle gene expression and on the incipient work that addresses three-dimensional genome architecture and its influence in cell fate determination and differentiation to achieve skeletal myogenesis. We will visit known alterations of genome organization mediated by chromosomal fusions giving rise to novel regulatory landscapes, enhancing oncogenic activation in muscle, such as alveolar rhabdomyosarcomas (ARMS).

Regulation of Ca v 3.1 channels by glucocorticoids.

The activity of low voltage-activated Ca(2+) (Ca(V)3) channels is tightly coupled to neurotransmitter and hormone secretion. Previous studies have shown that Ca(V)3 channels are regulated by glucocorticoids (GCs), though the mechanism underlying channel regulation remains unclear. Here, using the pituitary GH(3) cell line as a model, we investigated whether Ca(V)3 channel expression is under the control of GCs, and if their actions are mediated by transcriptional and/or post-transcriptional mechanisms. RT-PCR and western blot analyses showed that Ca(V)3.1 but not Ca(V)3.2 and Ca(V)3.3 channels is expressed in the GH(3) cells, and patch clamp recordings confirmed that Ca(2+) currents through low voltage-activated channels were decreased after chronic treatment with GCs. Consistent with this, total plasma membrane expression of Ca(V)3.1 protein as analyzed by cell-surface biotinylation assays and semi-quantitative western blotting was also down-regulated, while quantitative real-time RT-PCR analysis revealed a significant decrease of Ca(V)3.1 mRNA expression in the treated cells. In contrast, patch-clamp recordings on HEK-293 cells stably expressing recombinant Ca(V)3.1 channels showed that Ca(2+) currents were not affected by GC treatment. These results suggest that decreased transcription is a likely mechanism to explain the inhibitory actions of GCs on the functional expression of native Ca(V)3.1 channels.

From traditional biochemical signals to molecular markers for detection of sepsis after burn injuries.

Sepsis is a life-threatening organ-dysfunction condition caused by a dysregulated response to an infectious condition that can cause complications in patients with major trauma. Burns are one of the most destructive forms of trauma; despite the improvements in medical care, infections remain an important cause of burn injury-related mortality and morbidity, and complicated sepsis predisposes patients to diverse complications such as organ failure, lengthening of hospital stays, and increased costs. Accurate diagnosis and early treatment of sepsis may have a beneficial impact on clinical outcome of burn-injured patients. In this review, we offer a comprehensive description of the current and traditional markers used as indicative of sepsis in burned patients. However, although these are markers of the inflammatory post-burn response, they usually fail to predict sepsis in severely burned patients due to that they do not reflect the severity of the infection. Identification and measurement of biomarkers in early stages of infection is important in order to provide timely response and effective treatment of burned patients. Therefore, we compiled important experimental evidence, demonstrating novel biomarkers, including molecular markers such as genomic DNA variations, alterations of transcriptome profiling (mRNA, miRNAs, lncRNAs and circRNAs), epigenetic markers, and advances in proteomics and metabolomics. Finally, this review summarizes next-generation technologies for the identification of markers for detection of sepsis after burn injuries.

Wide Profiling of Circulating MicroRNAs in Spinocerebellar Ataxia Type 7.

Spinocerebellar ataxia type 7 (SCA7), a neurodegenerative disease characterized by cerebellar ataxia and retinal degeneration, is caused by a CAG repeat expansion in the ATXN7 gene coding region. Disease onset and progression are highly variable between patients, thus identification of specific/sensitive biomarkers that can improve the monitoring of disease progression is an immediate need. Because altered expression of circulating microRNAs (miRNAs) has been shown in various neurological diseases, they could be useful biomarkers for SCA7. In this study, we showed, to our knowledge for the first time, the expression profile of circulating miRNAs in SCA7. Using the TaqMan profiling low density array (TLDA), we found 71 differentially expressed miRNAs in the plasma of SCA7 patients, compared with healthy controls. The reliability of TLDA data was validated independently by quantitative real-time polymerase chain reaction in an independent cohort of patients and controls. We identified four validated miRNAs that possesses the diagnostic value to discriminate between healthy controls and patients (hsa-let-7a-5p, hsa-let7e-5p, hsa-miR-18a-5p, and hsa-miR-30b-5p). The target genes of these four miRNAs were significantly enriched in cellular processes that are relevant to central nervous system function, including Fas-mediated cell-death, heparansulfate biosynthesis, and soluble-N-ethylmaleimide-sensitive factor activating protein receptor pathways. Finally, we identify a signature of four miRNAs associated with disease severity that discriminate between early onset and adult onset, highlighting their potential utility to surveillance disease progression. In summary, circulating miRNAs might provide accessible biomarkers for disease stage and progression and help to identify novel cellular processes involved in SCA7.

Histamine-induced Ca2+ entry in human astrocytoma U373 MG cells: evidence for involvement of store-operated channels.

Glial and glia-derived cells express a variety of receptors for neurotransmitters and hormones, the majority of which evoke both Ca(2+) release from intracellular stores and Ca(2+) entry across the plasma membrane. We investigated the links between histamine H(1) receptor activation, Ca(2+) release from intracellular stores and Ca(2+) influx in human astrocytoma U373 MG cells. Histamine, through a H(1) receptor-mediated effect, evoked an increase in cytoplasmic free calcium concentration ([Ca(2+)](i)) that occurred in two phases: an initial, transient, increase owing to Ca(2+) mobilization from intracellular pools, and a second, sustained increase dependent on both Ca(2+) influx and continuous receptor occupancy. The characteristics of histamine-induced increases in [Ca(2+)](i) were similar to the capacitative entry evoked by emptying of the Ca(2+) stores with thapsigargine, and different from that observed when Ca(2+) influx was activated with OAG (1-oleoyl-2-acetyl-sn-glycerol), a diacylglycerol (DAG) analog. OAG application or increased endogenous DAG, resulting from DAG kinase inhibition, reduced the histamine-induced response. Furthermore, activation of the DAG target, protein kinase C (PKC), by TPA (12-O-tetradecanoyl 4beta-phorbol 13alpha-acetate) resulted in inhibition of the histamine-induced Ca(2+) response, an action prevented by PKC inhibitors. By using reverse transcriptase-polymerase chain reaction analysis, mRNAs for transient receptor potential channels (TRPCs) 1, 4, and 6 as well as for STIM1 (stromal-interacting molecule) and Orai1 were found to be expressed in the U373 MG cells, and confocal microscopy using specific antibodies revealed the presence of the corresponding proteins. Therefore, TRPCs may be candidate proteins forming store-operated channels in the U373 MG cell line. Further, our results confirm the involvement of PKC in the regulation of H(1) receptor-induced responses and point out to the existence of a feedback mechanism acting via PKC to limit the increase in [Ca(2+)](i).

Myotonic dystrophy CTG repeat expansion alters Ca2+ channel functional expression in PC12 cells.

We previously reported that expression of myotonic dystrophy (DM1) expanded CUG repeats impedes NGF-induced differentiation in a PC12 clone (CTG90 cells). Here, we present evidence for changes in the fractional contribution of distinct voltage-gated Ca(2+) channels, key elements in neurotrophin-promoted differentiation, to the total Ca(2+) current in the CTG90 cells. Patch-clamp recordings showed that the relative proportion of pharmacologically isolated Ca(2+) channel types differed between control and CTG90 cells. Particularly, the functional expression of N-type channels was significantly reduced. Though quantitative real-time RT-PCR revealed that transcripts for the pore-forming subunit encoding the N-type channels remained unchanged, the protein level analyzed by semi-quantitative Western blotting was down-regulated in the CTG90 cells. These data suggest modifications in the processing of N-type Ca(2+) channels in PC12 cells expressing the DM1 mutation.