SLC25A10 biallelic mutations in intractable epileptic encephalopathy with complex I deficiency.

Mitochondrial diseases are a plethora of inherited neuromuscular disorders sharing defects in mitochondrial respiration, but largely different from one another for genetic basis and pathogenic mechanism. Whole exome sequencing was performed in a familiar trio (trio-WES) with a child affected by severe epileptic encephalopathy associated with respiratory complex I deficiency and mitochondrial DNA depletion in skeletal muscle. By trio-WES we identified biallelic mutations in SLC25A10, a nuclear gene encoding a member of the mitochondrial carrier family. Genetic and functional analyses conducted on patient fibroblasts showed that SLC25A10 mutations are associated with reduction in RNA quantity and aberrant RNA splicing, and to absence of SLC25A10 protein and its transporting function. The yeast SLC25A10 ortholog knockout strain showed defects in mitochondrial respiration and mitochondrial DNA content, similarly to what observed in the patient skeletal muscle, and growth susceptibility to oxidative stress. Albeit patient fibroblasts were depleted in the main antioxidant molecules NADPH and glutathione, transport assays demonstrated that SLC25A10 is unable to transport glutathione. Here, we report the first recessive mutations of SLC25A10 associated to an inherited severe mitochondrial neurodegenerative disorder. We propose that SLC25A10 loss-of-function causes pathological disarrangements in respiratory-demanding conditions and oxidative stress vulnerability.

Nova regulates brain-specific splicing to shape the synapse.

Alternative RNA splicing greatly increases proteome diversity and may thereby contribute to tissue-specific functions. We carried out genome-wide quantitative analysis of alternative splicing using a custom Affymetrix microarray to assess the role of the neuronal splicing factor Nova in the brain. We used a stringent algorithm to identify 591 exons that were differentially spliced in the brain relative to immune tissues, and 6.6% of these showed major splicing defects in the neocortex of Nova2-/- mice. We tested 49 exons with the largest predicted Nova-dependent splicing changes and validated all 49 by RT-PCR. We analyzed the encoded proteins and found that all those with defined brain functions acted in the synapse (34 of 40, including neurotransmitter receptors, cation channels, adhesion and scaffold proteins) or in axon guidance (8 of 40). Moreover, of the 35 proteins with known interaction partners, 74% (26) interact with each other. Validating a large set of Nova RNA targets has led us to identify a multi-tiered network in which Nova regulates the exon content of RNAs encoding proteins that interact in the synapse.

A conserved RNA switch for acetylcholine receptor clustering at neuromuscular junctions in chordates.

In mammals, neuromuscular synapses rely on clustering of acetylcholine receptors (AChRs) in the muscle plasma membrane, ensuring optimal stimulation by motor neuron-released acetylcholine neurotransmitter. This clustering depends on a complex pathway based on alternative splicing of Agrin mRNAs by the RNA-binding proteins Nova1/2. Neuron-specific expression of Nova1/2 ensures the inclusion of small "Z" exons in Agrin, resulting in a neural-specific form of this extracellular proteoglycan carrying a short peptide motif that is required for binding to Lrp4 receptors on the muscle side, which in turn stimulate AChR clustering. Here we show that this intricate pathway is remarkably conserved in Ciona robusta, a non-vertebrate chordate in the tunicate subphylum. We use in vivo tissue-specific CRISPR/Cas9-mediated mutagenesis and heterologous "mini-gene" alternative splicing assays in cultured mammalian cells to show that Ciona Nova is also necessary and sufficient for Agrin Z exon inclusion and downstream AChR clustering. We present evidence that, although the overall pathway is well conserved, there are some surprising differences in Nova structure-function between Ciona and mammals. We further show that, in Ciona motor neurons, the transcription factor Ebf is a key activator of Nova expression, thus ultimately linking this RNA switch to a conserved, motor neuron-specific transcriptional regulatory network.

An RNA map predicting Nova-dependent splicing regulation.

Nova proteins are a neuron-specific alternative splicing factors. We have combined bioinformatics, biochemistry and genetics to derive an RNA map describing the rules by which Nova proteins regulate alternative splicing. This map revealed that the position of Nova binding sites (YCAY clusters) in a pre-messenger RNA determines the outcome of splicing. The map correctly predicted Nova's effect to inhibit or enhance exon inclusion, which led us to examine the relationship between the map and Nova's mechanism of action. Nova binding to an exonic YCAY cluster changed the protein complexes assembled on pre-mRNA, blocking U1 snRNP (small nuclear ribonucleoprotein) binding and exon inclusion, whereas Nova binding to an intronic YCAY cluster enhanced spliceosome assembly and exon inclusion. Assays of splicing intermediates of Nova-regulated transcripts in mouse brain revealed that Nova preferentially regulates removal of introns harbouring (or closest to) YCAY clusters. These results define a genome-wide map relating the position of a cis-acting element to its regulation by an RNA binding protein, namely that Nova binding to YCAY clusters results in a local and asymmetric action to regulate spliceosome assembly and alternative splicing in neurons.

Rescuing Z+ agrin splicing in Nova null mice restores synapse formation and unmasks a physiologic defect in motor neuron firing.

Synapse formation at the neuromuscular junction (NMJ) requires an alternatively spliced variant of agrin (Z(+) agrin) that is produced only by neurons. Here, we show that Nova1 and Nova2, neuron-specific splicing factors identified as targets in autoimmune motor disease, are essential regulators of Z(+) agrin. Nova1/Nova2 double knockout mice are paralyzed and fail to cluster AChRs at the NMJ, and breeding them with transgenic mice constitutively expressing Z(+) agrin in motor neurons rescued AChR clustering. Surprisingly, however, these rescued mice remained paralyzed, while electrophysiologic studies demonstrated that the motor axon and synapse were functional-spontaneous and evoked recordings revealed synaptic transmission and muscle contraction. These results point to a proximal defect in motor neuron firing in the absence of Nova and reveal a previously unsuspected role for RNA regulation in the physiologic activation of motor neurons.

Real-Time PCR Assay for the Analysis of Alternative Splicing of Immune Mediators in Cancer.

Alternative splicing evolved as a very efficient way to generate proteome diversity and to regulate cell homeostasis from a limited number of genes. Moreover, changes in the relative amounts of different splice variants derived from the same pre-mRNA are a hallmark in cancer, and aberrant expression of alternatively spliced mRNAs has been linked to cancer initiation and progression. Therefore, splice variants are critical tools to assess disease progression and clinical prognosis, and hold great promise as potential targets for therapeutic intervention. In order to understand the role that such splice variants play in cancer, it is vital to be able to accurately quantify their expression levels in different cell types and organs, both in normal conditions and in disease. In this chapter we describe a protocol to efficiently detect, analyze, and quantify alternative splicing patterns of immune mediators such as chemokines, cytokine and their receptors and ligands in cancer by quantitative PCR.

Helicobacter pylori eradication may influence timing of endoscopic surveillance for gastric cancer in patients with gastric precancerous lesions: A retrospective study.

Chronic atrophic gastritis and intestinal metaplasia related to Helicobacter pylori infection, are major risk factors for gastric adenocarcinoma. Eradication of H pylori and endoscopy surveillance of precancerous lesions may reduce the risk and/or lead to early detection of gastric cancer improving survival. In this study, the progression of precancerous lesions after H pylori treatment was evaluated.Patients with incomplete or complete intestinal metaplasia and/or gastric atrophy at the index endoscopy, were examined for the extension/histological worsening of precancerous lesions at the endoscopy surveillance for gastric cancer. Progression of lesions was evaluated according to H pylori status, age, and sex. Cox proportional hazard regression model and Kaplan-Meier curves were used to evaluate the strength of predictors for lesions progression.Among 105 patients (61 women) H pylori negative patients showed a milder worsening of gastric lesions between index and surveillance endoscopy compared with patients positive for the infection (log-rank test: P < .0001, P = .012, and P = .032 for antrum, angulus, and corpus, respectively). The Cox regression model showed persistence of H pylori infection (hazard ratio = 4.436; P < .0001) as the only relevant factor for lesion progression, whereas age >65 years and sex were not significant predictors.According to literature our results demonstrate that H pylori eradication is the major factor able to delay gastric precancerous lesions progression. Time interval for endoscopic surveillance in patients negative for H pylori infection and with gastric precancerous lesions may be extended.

NOVA2-mediated RNA regulation is required for axonal pathfinding during development.

The neuron specific RNA-binding proteins NOVA1 and NOVA2 are highly homologous alternative splicing regulators. NOVA proteins regulate at least 700 alternative splicing events in vivo, yet relatively little is known about the biologic consequences of NOVA action and in particular about functional differences between NOVA1 and NOVA2. Transcriptome-wide searches for isoform-specific functions, using NOVA1 and NOVA2 specific HITS-CLIP and RNA-seq data from mouse cortex lacking either NOVA isoform, reveals that NOVA2 uniquely regulates alternative splicing events of a series of axon guidance related genes during cortical development. Corresponding axonal pathfinding defects were specific to NOVA2 deficiency: Nova2-/- but not Nova1-/- mice had agenesis of the corpus callosum, and axonal outgrowth defects specific to ventral motoneuron axons and efferent innervation of the cochlea. Thus we have discovered that NOVA2 uniquely regulates alternative splicing of a coordinate set of transcripts encoding key components in cortical, brainstem and spinal axon guidance/outgrowth pathways during neural differentiation, with severe functional consequences in vivo.

Splicing Regulation of Pro-Inflammatory Cytokines and Chemokines: At the Interface of the Neuroendocrine and Immune Systems.

Alternative splicing plays a key role in posttranscriptional regulation of gene expression, allowing a single gene to encode multiple protein isoforms. As such, alternative splicing amplifies the coding capacity of the genome enormously, generates protein diversity, and alters protein function. More than 90% of human genes undergo alternative splicing, and alternative splicing is especially prevalent in the nervous and immune systems, tissues where cells need to react swiftly and adapt to changes in the environment through carefully regulated mechanisms of cell differentiation, migration, targeting, and activation. Given its prevalence and complexity, this highly regulated mode of gene expression is prone to be affected by disease. In the following review, we look at how alternative splicing of signaling molecules­cytokines and their receptors­changes in different pathological conditions, from chronic inflammation to neurologic disorders, providing means of functional interaction between the immune and neuroendocrine systems. Switches in alternative splicing patterns can be very dynamic and can produce signaling molecules with distinct or antagonistic functions and localization to different subcellular compartments. This newly discovered link expands our understanding of the biology of immune and neuroendocrine cells, and has the potential to open new windows of opportunity for treatment of neurodegenerative disorders.

Duodenal switch without gastric resection: results and observations after 6 years.

BACKGROUND: The results on metabolic effects of the classical biliopancreatic diversion (BPD) have led us to investigate the operation without gastric resection, thus preserving stomach and pylorus, in patients who are not seriously obese but suffer from hypercholesterolemia, often associated with type 2 diabetes and hypertriglyceridemia. METHODS: Between 1996 and 1999, we performed the duodenal switch (DS) without gastric resection on 24 mildly obese patients. Mean preoperative BMI was 36.2 kg/m(2). 17 patients (70.8%) suffered from type 1 diabetes, 4 (16.6%) had impaired glucose tolerance, while the remainder had fasting hyperglycemia. In 20 patients (83.3%), hypercholesterolemia and alterations in lipid profile were present. Another 20 patients were taking drugs for arterial hypertension. The pluri-metabolic syndrome was present in 41.6% of patients. RESULTS: Mean follow-up was 4 years. BMI reduction and weight loss were not large. 2 patients who had severe longstanding diabetes type 2 needed a second operation of the classical BPD because of failure in improving diabetes. Another 2 patients were changed to classical BPD because of a relapsing chronic duodeno-ileal ulcer. The incidence of ileal ulcer was 29.1%. Regarding hypercholesterolemia, hypertrigliceridemia, and type 2 diabetes when there is a good pancreatic "reservoir", the operation seems effective in the long-term. Protein absorption is better than that obtained with the classical BPD. CONCLUSIONS: Our long-term results suggest that in carefully selected patients suffering from serious hypercholesterolemia or type 2 diabetes with insulin reserves still at an acceptable level, and with BMI 30-40, DS without gastric resection can be proposed as a surgical treatment for metabolic diseases but not for obesity.

Radiolabeled semi-quantitative RT-PCR assay for the analysis of alternative splicing of interleukin genes.

Alternative splicing evolved as a very efficient way to generate proteome diversity from a limited number of genes, while at the same time modulating posttranscriptional events of gene expression-such as stability, turnover, subcellular localization, binding properties, and general activity of both mRNAs and proteins. Since the vast majority of human genes undergo alternative splicing, it comes to no surprise that interleukin genes also show extensive alternative splicing. In fact, there is a growing body of evidence indicating that alternative splicing plays a central role in modulating the pleiotropic functions of cytokines, and aberrant expression of alternatively spliced interleukin mRNAs has been linked to disease. However, while several interleukin splice variants have been described, their function is still poorly understood. This is particularly relevant, since alternatively spliced cytokine isoforms can act both as disease biomarkers and as candidate entry points for therapeutic intervention. In this chapter we describe a protocol that uses radiolabeled semi-quantitative RT-PCR to efficiently detect, analyze, and quantify alternative splicing patterns of cytokine genes.

Is sternotomy always necessary for the treatment of mediastinal ectopic thyroid goiter?

UNLABELLED: Ectopic thyroid goiter accounts approximately for 1% of all substernal goiters and for 10-15% of all mediastinal masses. Sternotomy is generally accepted as the most adequate approach for the removal of ectopic thyroid goiters of the anterior mediastinum. We report two cases of mediastinal ectopic goiter removal through a cervical incision, without sternotomy. The technique is based on a careful and gentle traction of the mass by means of traction stitches and simultaneously on a blunt digital dissection, in order to exteriorize the lesion in the neck, as much as necessary to ligate its vascular pedicle before completing the removal. When performed with caution and precision, this approach can avoid sternotomy in selected patients with ectopic thyroid goiter. KEY WORDS: Ectopic thyroid, Sternotomy, Thyroidectomy.

A role for SMN exon 7 splicing in the selective vulnerability of motor neurons in spinal muscular atrophy.

Spinal muscular atrophy (SMA) is an inherited motor neuron disease caused by homozygous loss of the Survival Motor Neuron 1 (SMN1) gene. In the absence of SMN1, inefficient inclusion of exon 7 in transcripts from the nearly identical SMN2 gene results in ubiquitous SMN decrease but selective motor neuron degeneration. Here we investigated whether cell type-specific differences in the efficiency of exon 7 splicing contribute to the vulnerability of SMA motor neurons. We show that normal motor neurons express markedly lower levels of full-length SMN mRNA from SMN2 than do other cells in the spinal cord. This is due to inefficient exon 7 splicing that is intrinsic to motor neurons under normal conditions. We also find that SMN depletion in mammalian cells decreases exon 7 inclusion through a negative feedback loop affecting the splicing of its own mRNA. This mechanism is active in vivo and further decreases the efficiency of exon 7 inclusion specifically in motor neurons of severe-SMA mice. Consistent with expression of lower levels of full-length SMN, we find that SMN-dependent downstream molecular defects are exacerbated in SMA motor neurons. These findings suggest a mechanism to explain the selective vulnerability of motor neurons to loss of SMN1.

Integrative modeling defines the Nova splicing-regulatory network and its combinatorial controls.

The control of RNA alternative splicing is critical for generating biological diversity. Despite emerging genome-wide technologies to study RNA complexity, reliable and comprehensive RNA-regulatory networks have not been defined. Here, we used Bayesian networks to probabilistically model diverse data sets and predict the target networks of specific regulators. We applied this strategy to identify approximately 700 alternative splicing events directly regulated by the neuron-specific factor Nova in the mouse brain, integrating RNA-binding data, splicing microarray data, Nova-binding motifs, and evolutionary signatures. The resulting integrative network revealed combinatorial regulation by Nova and the neuronal splicing factor Fox, interplay between phosphorylation and splicing, and potential links to neurologic disease. Thus, we have developed a general approach to understanding mammalian RNA regulation at the systems level.

Alternative splicing microarrays reveal functional expression of neuron-specific regulators in Hodgkin lymphoma cells.

Alternative splicing provides a versatile mechanism of gene regulation, which is often subverted in disease. We have used customized oligonucleotide microarrays to interrogate simultaneously the levels of expression of splicing factors and the patterns of alternative splicing of genes involved in tumor progression. Analysis of RNAs isolated from cell lines derived from Hodgkin lymphoma tumors indicate that the relative abundance of alternatively spliced isoforms correlates with transformation and tumor grade. Changes in expression of regulators were also detected, and a subset sample was confirmed at the protein level. Ectopic expression of neuron-specific splicing regulatory proteins of the Nova family was observed in some cell lines and tumor samples, correlating with expression of a neuron-specific mRNA isoform of JNK2 kinase. This microarray design can help assess the role of alternative splicing in a variety of biological and medical problems and potentially serve as a diagnostic tool.

Common molecular pathways mediate long-term potentiation of synaptic excitation and slow synaptic inhibition.

Synaptic plasticity, the cellular correlate for learning and memory, involves signaling cascades in the dendritic spine. Extensive studies have shown that long-term potentiation (LTP) of the excitatory postsynaptic current (EPSC) through glutamate receptors is induced by activation of N-methyl-D-asparate receptor (NMDA-R)--the coincidence detector--and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Here we report that the same signaling pathway in the postsynaptic CA1 pyramidal neuron also causes LTP of the slow inhibitory postsynaptic current (sIPSC) mediated by metabotropic GABA(B) receptors (GABA(B)-Rs) and G protein-activated inwardly rectifying K(+) (GIRK) channels, both residing in dendritic spines as well as shafts. Indicative of intriguing differences in the regulatory mechanisms for excitatory and inhibitory synaptic plasticity, LTP of sIPSC but not EPSC was abolished in mice lacking Nova-2, a neuronal-specific RNA binding protein that is an autoimmune target in paraneoplastic opsoclonus myoclonus ataxia (POMA) patients with latent cancer, reduced inhibitory control of movements, and dementia.

CLIP identifies Nova-regulated RNA networks in the brain.

Nova proteins are neuron-specific antigens targeted in paraneoplastic opsoclonus myoclonus ataxia (POMA), an autoimmune neurologic disease characterized by abnormal motor inhibition. Nova proteins regulate neuronal pre-messenger RNA splicing by directly binding to RNA. To identify Nova RNA targets, we developed a method to purify protein-RNA complexes from mouse brain with the use of ultraviolet cross-linking and immunoprecipitation (CLIP).Thirty-four transcripts were identified multiple times by Nova CLIP.Three-quarters of these encode proteins that function at the neuronal synapse, and one-third are involved in neuronal inhibition.Splicing targets confirmed in Nova-/- mice include c-Jun N-terminal kinase 2, neogenin, and gephyrin; the latter encodes a protein that clusters inhibitory gamma-aminobutyric acid and glycine receptors, two previously identified Nova splicing targets.Thus, CLIP reveals that Nova coordinately regulates a biologically coherent set of RNAs encoding multiple components of the inhibitory synapse, an observation that may relate to the cause of abnormal motor inhibition in POMA.