Mutation in archain 1, a subunit of COPI coatomer complex, causes diluted coat color and Purkinje cell degeneration

An In Vitro Model of Glioma Development

Gliomas are the prevalent forms of brain cancer and derive from glial cells. Among them, astrocytomas are the most frequent. Astrocytes are fundamental for most brain functions, as they contribute to neuronal metabolism and neurotransmission. When they acquire cancer properties, their functions are altered, and, in addition, they start invading the brain parenchyma. Thus, a better knowledge of transformed astrocyte molecular properties is essential. With this aim, we previously developed rat astrocyte clones with increasing cancer properties. In this study, we used proteomic analysis to compare the most transformed clone (A-FC6) with normal primary astrocytes. We found that 154 proteins are downregulated and 101 upregulated in the clone. Moreover, 46 proteins are only expressed in the clone and 82 only in the normal cells. Notably, only 11 upregulated/unique proteins are encoded in the duplicated q arm of isochromosome 8 (i(8q)), which cytogenetically characterizes the clone. Since both normal and transformed brain cells release extracellular vesicles (EVs), which might induce epigenetic modifications in the neighboring cells, we also compared EVs released from transformed and normal astrocytes. Interestingly, we found that the clone releases EVs containing proteins, such as matrix metalloproteinase 3 (MMP3), that can modify the extracellular matrix, thus allowing invasion.

Identification of mutant gene for Black crystal coat and non-allelic gene interactions in Neogale vison

Sable (Martes zibellina) and American mink (Neogale vison) are valuable species characterized by a variety of coat colour produced on fur farms. Black crystal fur phenotype is Mendelian codominant trait: heterozygous animals (C^r/ +) have white guard hairs scattered predominantly on the spine and the head, while homozygous (C^r/C^r) minks have coats resembling the Himalayan (c^h/c^h) or white Hedlund (h/h) types. It is one of the most recent of more than 35 currently known phenotypic traits of fur colour in American mink. Black crystal fur phenotype was first described in 1984 in the Russian population of mink, which had undergone selection for domestic defensive response to humans. Here, we performed whole-genome sequencing of American mink with C^r/C^r phenotype. We identified a missense mutation in the gene encoding the α-COP subunit of the COPI complex (COPA). The COPI complex mediates retrograde trafficking from the Golgi system to the endoplasmic reticulum and sorting of transmembrane proteins. We observed an interaction between a newly identified mutation in the COPA gene and a mutation in the microphthalmia-associated transcription factor (MITF), the latter mutation led to the formation of the white Hedlund (h/h) phenotype. Double heterozygotes for these mutations have an entirely white coat and a black-eyed phenotype similar to the phenotype of C^r/C^r or h/h minks. Our data could be useful for tracking economically valuable fur traits in mink breeding programs to contribute to global fur production.

Lipid Dyshomeostasis and Inherited Cerebellar Ataxia

Cerebellar ataxia is a form of ataxia that originates from dysfunction of the cerebellum, but may involve additional neurological tissues. Its clinical symptoms are mainly characterized by the absence of voluntary muscle coordination and loss of control of movement with varying manifestations due to differences in severity, in the site of cerebellar damage and in the involvement of extracerebellar tissues. Cerebellar ataxia may be sporadic, acquired, and hereditary. Hereditary ataxia accounts for the majority of cases. Hereditary ataxia has been tentatively divided into several subtypes by scientists in the field, and nearly all of them remain incurable. This is mainly because the detailed mechanisms of these cerebellar disorders are incompletely understood. To precisely diagnose and treat these diseases, studies on their molecular mechanisms have been conducted extensively in the past. Accumulating evidence has demonstrated that some common pathogenic mechanisms exist within each subtype of inherited ataxia. However, no reports have indicated whether there is a common mechanism among the different subtypes of inherited cerebellar ataxia. In this review, we summarize the available references and databases on neurological disorders characterized by cerebellar ataxia and show that a subset of genes involved in lipid homeostasis form a new group that may cause ataxic disorders through a common mechanism. This common signaling pathway can provide a valuable reference for future diagnosis and treatment of ataxic disorders.

Craniofacial Diseases Caused by Defects in Intracellular Trafficking

Cells use membrane-bound carriers to transport cargo molecules like membrane proteins and soluble proteins, to their destinations. Many signaling receptors and ligands are synthesized in the endoplasmic reticulum and are transported to their destinations through intracellular trafficking pathways. Some of the signaling molecules play a critical role in craniofacial morphogenesis. Not surprisingly, variants in the genes encoding intracellular trafficking machinery can cause craniofacial diseases. Despite the fundamental importance of the trafficking pathways in craniofacial morphogenesis, relatively less emphasis is placed on this topic, thus far. Here, we describe craniofacial diseases caused by lesions in the intracellular trafficking machinery and possible treatment strategies for such diseases.

Defects in early secretory pathway transport machinery components and neurodevelopmental disorders

The early secretory pathway, provisionally comprising of vesicular traffic between the endoplasmic reticulum (ER) and the Golgi apparatus, occurs constitutively in mammalian cells. Critical for a constant supply of secretory and plasma membrane (PM) materials, the pathway is presumably essential for general cellular function and survival. Neurons exhibit a high intensity in membrane dynamics and protein/lipid trafficking, with differential and polarized trafficking towards the somatodendritic and axonal PM domains. Mutations in genes encoding early secretory pathway membrane trafficking machinery components are known to result in neurodevelopmental or neurological disorders with disease manifestation in early life. Here, such rare disorders associated with autosomal recessive mutations in coat proteins, membrane tethering complexes and membrane fusion machineries responsible for trafficking in the early secretory pathway are summarily discussed. These mutations affected genes encoding subunits of coat protein complex I and II, subunits of transport protein particle (TRAPP) complexes, members of the YIP1 domain family (YIPF) and a SNAP receptor (SNARE) family member. Why the ubiquitously present and constitutively acting early secretory pathway machinery components could specifically affect neurodevelopment is addressed, with the plausible underlying disease etiologies and neuropathological mechanisms resulting from these mutations explored.

Mutations in the COPI coatomer subunit α-COP induce release of Aβ-42 and amyloid precursor protein intracellular domain and increase tau oligomerization and release

Understanding the cellular processes that lead to Alzheimer's disease (AD) is critical, and one key lies in the genetics of families with histories of AD. Mutations a complex known as COPI were found in families with AD. The COPI complex is involved in protein processing and trafficking. Intriguingly, several recent publications have found components of the COPI complex can affect the metabolism of pathogenic AD proteins. We reduced levels of the COPI subunit α-COP, altering maturation and cleavage of amyloid precursor protein (APP), resulting in decreased release of Aβ-42 and decreased accumulation of the AICD. Depletion of α-COP reduced uptake of proteopathic Tau seeds and reduces intracellular Tau self-association. Expression of AD-associated mutant α-COP altered APP processing, resulting in increased release of Aβ-42 and increased intracellular Tau aggregation and release of Tau oligomers. These results show that COPI coatomer function modulates processing of both APP and Tau, and expression of AD-associated α-COP confers a toxic gain of function, resulting in potentially pathogenic changes in both APP and Tau.

A paralog-specific role of COPI vesicles in the neuronal differentiation of mouse pluripotent cells

The paralogous COPI coat subunit γ1-COP plays a unique role in promoting neurite outgrowth during the neuronal differentiation of mouse pluripotent cells.

Coat protein complex I (COPI)–coated vesicles mediate membrane trafficking between Golgi cisternae as well as retrieval of proteins from the Golgi to the endoplasmic reticulum. There are several flavors of the COPI coat defined by paralogous subunits of the protein complex coatomer. However, whether paralogous COPI proteins have specific functions is currently unknown. Here, we show that the paralogous coatomer subunits γ1-COP and γ2-COP are differentially expressed during the neuronal differentiation of mouse pluripotent cells. Moreover, through a combination of genome editing experiments, we demonstrate that whereas γ-COP paralogs are largely functionally redundant, γ1-COP specifically promotes neurite outgrowth. Our work stresses a role of the COPI pathway in neuronal polarization and provides evidence for distinct functions for coatomer paralogous subunits in this process.

SCYL1 arginine methylation by PRMT1 is essential for neurite outgrowth via Golgi morphogenesis

Arginine methylation is a common posttranslational modification that modulates protein function. SCY1-like pseudokinase 1 (SCYL1) is crucial for neuronal functions and interacts with γ₂-COP to form coat protein complex I (COPI) vesicles that regulate Golgi morphology. However, the molecular mechanism by which SCYL1 is regulated remains unclear. Here, we report that the γ₂-COP-binding site of SCYL1 is arginine-methylated by protein arginine methyltransferase 1 (PRMT1) and that SCYL1 arginine methylation is important for the interaction of SCYL1 with γ₂-COP. PRMT1 was colocalized with SCYL1 in the Golgi fraction. Inhibition of PRMT1 suppressed axon outgrowth and dendrite complexity via abnormal Golgi morphology. Knockdown of SCYL1 by small interfering RNA (siRNA) inhibited axon outgrowth, and the inhibitory effect was rescued by siRNA-resistant SCYL1, but not SCYL1 mutant, in which the arginine methylation site was replaced. Thus, PRMT1 regulates Golgi morphogenesis via SCYL1 arginine methylation. We propose that SCYL1 arginine methylation by PRMT1 contributes to axon and dendrite morphogenesis in neurons.

Oligomeric amyloid-β induces early and widespread changes to the proteome in human iPSC-derived neurons

Alzheimer's disease (AD) is the most common form of dementia globally and is characterized by aberrant accumulations of amyloid-beta (Aβ) and tau proteins. Oligomeric forms of these proteins are believed to be most relevant to disease progression, with oligomeric amyloid-β (oAβ) particularly implicated in AD. oAβ pathology spreads among interconnected brain regions, but how oAβ induces pathology in these previously unaffected neurons requires further study. Here, we use well characterized iPSC-derived human neurons to study the early changes to the proteome and phosphoproteome after 24 h exposure to oAβ 1-42. Using nLC-MS/MS and label-free quantification, we identified several proteins that are differentially regulated in response to acute oAβ challenge. At this early timepoint, oAβ induced the decrease of TDP-43, heterogeneous nuclear ribonucleoproteins (hnRNPs), and coatomer complex I (COPI) proteins. Conversely, increases were observed in 20 S proteasome subunits and vesicle associated proteins VAMP1/2, as well as the differential phosphorylation of tau at serine 208. These changes show that there are widespread alterations to the neuronal proteome within 24 h of oAβ uptake, including proteins previously not shown to be related to neurodegeneration. This study provides new targets for the further study of early mediators of AD pathogenesis.

Quantitative proteomics identifies proteins that resist translational repression and become dysregulated in ALS-FUS

Aberrant translational repression is a feature of multiple neurodegenerative diseases. The association between disease-linked proteins and stress granules further implicates impaired stress responses in neurodegeneration. However, our knowledge of the proteins that evade translational repression is incomplete. It is also unclear whether disease-linked proteins influence the proteome under conditions of translational repression. To address these questions, a quantitative proteomics approach was used to identify proteins that evade stress-induced translational repression in arsenite-treated cells expressing either wild-type or amyotrophic lateral sclerosis (ALS)-linked mutant FUS. This study revealed hundreds of proteins that are actively synthesized during stress-induced translational repression, irrespective of FUS genotype. In addition to proteins involved in RNA- and protein-processing, proteins associated with neurodegenerative diseases such as ALS were also actively synthesized during stress. Protein synthesis under stress was largely unperturbed by mutant FUS, although several proteins were found to be differentially expressed between mutant and control cells. One protein in particular, COPBI, was downregulated in mutant FUS-expressing cells under stress. COPBI is the beta subunit of the coat protein I (COPI), which is involved in Golgi to endoplasmic reticulum (ER) retrograde transport. Further investigation revealed reduced levels of other COPI subunit proteins and defects in COPBI-relatedprocesses in cells expressing mutant FUS. Even in the absence of stress, COPBI localization was altered in primary and human stem cell-derived neurons expressing ALS-linked FUS variants. Our results suggest that Golgi to ER retrograde transport may be important under conditions of stress and is perturbed upon the expression of disease-linked proteins such as FUS.

Murine obscurin and Obsl1 have functionally redundant roles in sarcolemmal integrity, sarcoplasmic reticulum organization, and muscle metabolism

Biological roles of obscurin and its close homolog Obsl1 (obscurin-like 1) have been enigmatic. While obscurin is highly expressed in striated muscles, Obsl1 is found ubiquitously. Accordingly, obscurin mutations have been linked to myopathies, whereas mutations in Obsl1 result in 3M-growth syndrome. To further study unique and redundant functions of these closely related proteins, we generated and characterized Obsl1 knockouts. Global Obsl1 knockouts are embryonically lethal. In contrast, skeletal muscle-specific Obsl1 knockouts show a benign phenotype similar to obscurin knockouts. Only deletion of both proteins and removal of their functional redundancy revealed their roles for sarcolemmal stability and sarcoplasmic reticulum organization. To gain unbiased insights into changes to the muscle proteome, we analyzed tibialis anterior and soleus muscles by mass spectrometry, uncovering additional changes to the muscle metabolism. Our analyses suggest that all obscurin protein family members play functions for muscle membrane systems.

Abnormal Golgi morphology and decreased COPI function in cells with low levels of SMN

We report here the finding of abnormal Golgi apparatus morphology in motor neuron like cells depleted of SMN as well as Golgi apparatus morphology in SMA patient fibroblasts. Rescue experiments demonstrate that this abnormality is dependent on SMN, but can also be rescued by expression of the COPI coatomer subunit alpha-COP. A motor neuron-like cell line containing an inducible alpha-COP shRNA was created to generate a parallel system to study knockdown of SMN or alpha-COP. Multiple assays of COPI-dependent intracellular trafficking in cells depleted of SMN demonstrate that alpha-COP function is suboptimal, including failed sequestration of plasma membrane proteins, altered binding of mRNA, and defective targeting and transport of Golgi-resident proteins.

Advancements in Host-Based Interventions for Influenza Treatment

Influenza is a major acute respiratory infection that causes mortality and morbidity worldwide. Two classes of conventional antivirals, M2 ion channel blockers and neuraminidase inhibitors, are mainstays in managing influenza disease to lessen symptoms while minimizing hospitalization and death in patients with severe influenza. However, the development of viral resistance to both drug classes has become a major public health concern. Vaccines are prophylaxis mainstays but are limited in efficacy due to the difficulty in matching predicted dominant viral strains to circulating strains. As such, other potential interventions are being explored. Since viruses rely on host cellular functions to replicate, recent therapeutic developments focus on targeting host factors involved in virus replication. Besides controlling virus replication, potential targets for drug development include controlling virus-induced host immune responses such as the recently suggested involvement of innate lymphoid cells and NADPH oxidases in influenza virus pathogenesis and immune cell metabolism. In this review, we will discuss the advancements in novel host-based interventions for treating influenza disease.

Formation of COPI-coated vesicles at a glance

The coat protein complex I (COPI) allows the precise sorting of lipids and proteins between Golgi cisternae and retrieval from the Golgi to the ER. This essential role maintains the identity of the early secretory pathway and impinges on key cellular processes, such as protein quality control. In this Cell Science at a Glance and accompanying poster, we illustrate the different stages of COPI-coated vesicle formation and revisit decades of research in the context of recent advances in the elucidation of COPI coat structure. By calling attention to an array of questions that have remained unresolved, this review attempts to refocus the perspectives of the field.

Rapid Discovery of De Novo Deleterious Mutations in Cattle Enhances the Value of Livestock as Model Species

In humans, the clinical and molecular characterization of sporadic syndromes is often hindered by the small number of patients and the difficulty in developing animal models for severe dominant conditions. Here we show that the availability of large data sets of whole-genome sequences, high-density SNP chip genotypes and extensive recording of phenotype offers an unprecedented opportunity to quickly dissect the genetic architecture of severe dominant conditions in livestock. We report on the identification of seven dominant de novo mutations in CHD7, COL1A1, COL2A1, COPA, and MITF and exploit the structure of cattle populations to describe their clinical consequences and map modifier loci. Moreover, we demonstrate that the emergence of recessive genetic defects can be monitored by detecting de novo deleterious mutations in the genome of bulls used for artificial insemination. These results demonstrate the attractiveness of cattle as a model species in the post genomic era, particularly to confirm the genetic aetiology of isolated clinical case reports in humans.

Pilot study of large-scale production of mutant pigs by ENU mutagenesis

N-ethyl-N-nitrosourea (ENU) mutagenesis is a powerful tool to generate mutants on a large scale efficiently, and to discover genes with novel functions at the whole-genome level in Caenorhabditis elegans, flies, zebrafish and mice, but it has never been tried in large model animals. We describe a successful systematic three-generation ENU mutagenesis screening in pigs with the establishment of the Chinese Swine Mutagenesis Consortium. A total of 6,770 G1 and 6,800 G3 pigs were screened, 36 dominant and 91 recessive novel pig families with various phenotypes were established. The causative mutations in 10 mutant families were further mapped. As examples, the mutation of SOX10 (R109W) in pig causes inner ear malfunctions and mimics human Mondini dysplasia, and upregulated expression of FBXO32 is associated with congenital splay legs. This study demonstrates the feasibility of artificial random mutagenesis in pigs and opens an avenue for generating a reservoir of mutants for agricultural production and biomedical research.

DOI:http://dx.doi.org/10.7554/eLife.26248.001

ARCN1 Mutations Cause a Recognizable Craniofacial Syndrome Due to COPI-Mediated Transport Defects

Cellular homeostasis is maintained by the highly organized cooperation of intracellular trafficking systems, including COPI, COPII, and clathrin complexes. COPI is a coatomer protein complex responsible for intracellular protein transport between the endoplasmic reticulum and the Golgi apparatus. The importance of such intracellular transport mechanisms is underscored by the various disorders, including skeletal disorders such as cranio-lenticulo-sutural dysplasia and osteogenesis imperfect, caused by mutations in the COPII coatomer complex. In this article, we report a clinically recognizable craniofacial disorder characterized by facial dysmorphisms, severe micrognathia, rhizomelic shortening, microcephalic dwarfism, and mild developmental delay due to loss-of-function heterozygous mutations in ARCN1, which encodes the coatomer subunit delta of COPI. ARCN1 mutant cell lines were revealed to have endoplasmic reticulum stress, suggesting the involvement of ER stress response in the pathogenesis of this disorder. Given that ARCN1 deficiency causes defective type I collagen transport, reduction of collagen secretion represents the likely mechanism underlying the skeletal phenotype that characterizes this condition. Our findings demonstrate the importance of COPI-mediated transport in human development, including skeletogenesis and brain growth.

δ-COP contains a helix C-terminal to its longin domain key to COPI dynamics and function

Membrane recruitment of coatomer and formation of coat protein I (COPI)-coated vesicles is crucial to homeostasis in the early secretory pathway. The conformational dynamics of COPI during cargo capture and vesicle formation is incompletely understood. By scanning the length of δ-COP via functional complementation in yeast, we dissect the domains of the δ-COP subunit. We show that the μ-homology domain is dispensable for COPI function in the early secretory pathway, whereas the N-terminal longin domain is essential. We map a previously uncharacterized helix, C-terminal to the longin domain, that is specifically required for the retrieval of HDEL-bearing endoplasmic reticulum-luminal residents. It is positionally analogous to an unstructured linker that becomes helical and membrane-facing in the open form of the AP2 clathrin adaptor complex. Based on the amphipathic nature of the critical helix it may probe the membrane for lipid packing defects or mediate interaction with cargo and thus contribute to stabilizing membrane-associated coatomer.

Relevance of the COPI complex for Alzheimer's disease progression in vivo

Cellular trafficking and recycling machineries belonging to late secretory compartments have been associated with increased Alzheimer's disease (AD) risk. We have shown that coat protein complex I (COPI)-dependent trafficking, an early step in Golgi-to-endoplasmic reticulum retrograde transport, affects amyloid precursor protein subcellular localization, cell-surface expression, as well as its metabolism. We present here a set of experiments demonstrating that, by targeting subunit δ-COP function, the moderation of the COPI-dependent trafficking in vivo leads to a significant decrease in amyloid plaques in the cortex and hippocampus of neurological 17 mice crossed with the 2xTg AD mouse model. Remarkably, an improvement of the memory impairments was also observed. Importantly, human genetic association studies of different AD cohorts led to the identification of 12 SNPs and 24 mutations located in COPI genes linked to an increased AD risk. These findings further demonstrate in vivo the importance of early trafficking steps in AD pathogenesis and open new clinical perspectives.

α-COP binding to the survival motor neuron protein SMN is required for neuronal process outgrowth

Spinal muscular atrophy (SMA), a heritable neurodegenerative disease, results from insufficient levels of the survival motor neuron (SMN) protein. α-COP binds to SMN, linking the COPI vesicular transport pathway to SMA. Reduced levels of α-COP restricted development of neuronal processes in NSC-34 cells and primary cortical neurons. Remarkably, heterologous expression of human α-COP restored normal neurite length and morphology in SMN-depleted NSC-34 cells in vitro and zebrafish motor neurons in vivo. We identified single amino acid mutants of α-COP that selectively abrogate SMN binding, retain COPI-mediated Golgi-ER trafficking functionality, but were unable to support neurite outgrowth in cellular and zebrafish models of SMA. Taken together, these demonstrate the functional role of COPI association with the SMN protein in neuronal development.

Mycobacterium avium MAV_2941 mimics phosphoinositol-3-kinase to interfere with macrophage phagosome maturation

Mycobacterium avium subsp hominissuis (M. avium) is a pathogen that infects and survives in macrophages. Previously, we have identified the M. avium MAV_2941 gene encoding a 73 amino acid protein exported by the oligopeptide transporter OppA to the macrophage cytoplasm. Mutations in MAV_2941 were associated with significant impairment of M. avium growth in THP-1 macrophages. In this study, we investigated the molecular mechanism of MAV_2941 action and demonstrated that MAV_2941 interacts with the vesicle trafficking proteins syntaxin-8 (STX8), adaptor-related protein complex 3 (AP-3) complex subunit beta-1 (AP3B1) and Archain 1 (ARCN1) in mononuclear phagocytic cells. Sequencing analysis revealed that the binding site of MAV_2941 is structurally homologous to the human phosphatidylinositol 3-kinase (PI3K) chiefly in the region recognized by vesicle trafficking proteins. The β3A subunit of AP-3, encoded by AP3B1, is essential for trafficking cargo proteins, including lysosomal-associated membrane protein 1 (LAMP-1), to the phagosome and lysosome-related organelles. Here, we show that while the heat-killed M. avium when ingested by macrophages co-localizes with LAMP-1 protein, transfection of MAV_2941 in macrophages results in significant decrease of LAMP-1 co-localization with the heat-killed M. avium phagosomes. Mutated MAV_2941, where the amino acids homologous to the binding region of PI3K were changed, failed to interact with trafficking proteins. Inactivation of the AP3B1 gene led to alteration in the trafficking of LAMP-1. These results suggest that M. avium MAV_2941 interferes with the protein trafficking within macrophages altering the maturation of phagosome.

Structure of the bovine COPI δ subunit μ homology domain at 2.15 Å resolution

The heptameric COPI coat (coatomer) plays an essential role in vesicular transport in the early secretory system of eukaryotic cells. While the structures of some of the subunits have been determined, that of the δ-COP subunit has not been reported to date. The δ-COP subunit is part of a subcomplex with structural similarity to tetrameric clathrin adaptors (APs), where δ-COP is the structural homologue of the AP μ subunit. Here, the crystal structure of the μ homology domain (MHD) of δ-COP (δ-MHD) obtained by phasing using a combined SAD-MR method is presented at 2.15 Å resolution. The crystallographic asymmetric unit contains two monomers that exhibit short sections of disorder, which may allude to flexible regions of the protein. The δ-MHD is composed of two subdomains connected by unstructured linkers. Comparison between this structure and those of known MHD domains from the APs shows significant differences in the positions of specific loops and β-sheets, as well as a more general change in the relative positions of the protein subdomains. The identified difference may be the major source of cargo-binding specificity. Finally, the crystal structure is used to analyze the potential effect of the I422T mutation in δ-COP previously reported to cause a neurodegenerative phenotype in mice.

RNA interference mediated knockdown of the KDEL receptor and COPB2 inhibits digestion and reproduction in the parasitic copepod Lepeophtheirus salmonis

Retrograde transport of proteins from the endoplasmic reticulum to the Golgi is an essential part of the secretory pathway that all newly synthesised secreted and membrane proteins in eukaryotic cells undergo. The aim of this study was to characterise two components of the retrograde transport pathway in the parasitic copepod Lepeophtheirus salmonis (salmon louse) on a molecular and functional level. LsKDELR and LsCOPB2 were confirmed to be the salmon louse homologues of the chosen target proteins by sequence similarity. Ontogenetic analysis by qRT-PCR revealed the highest expression levels of both genes in adult females and the earliest larval stage. LsKDELR and LsCOPB2 localisation in adult females was detected by immunofluorescence and in situ hybridisation, respectively. Both LsKDELR and LsCOPB2 were found in the ovaries, the oocytes and the gut. LsKDELR and LsCOPB2 were knocked down by RNA interference in preadult females, which was confirmed by qRT-PCR. LsCOPB2 knockdown lice had a significantly higher mortality and failed to develop normally, while both LsCOPB2 and LsKDELR knockdown caused disturbed digestion and the absence of egg strings. This shows the potential of LsKDELR and LsCOPB2 as suitable target candidates for new pest control methods.

Dilysine motifs in exon 2b of SMN protein mediate binding to the COPI vesicle protein α-COP and neurite outgrowth in a cell culture model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder that stems from low levels of survival of motor neuron (SMN) protein. The processes that cause motor neurons and muscle cells to become dysfunctional are incompletely understood. We are interested in neuromuscular homeostasis and the stresses put upon that system by loss of SMN. We recently reported that α-COP, a member of the coatomer complex of coat protein I (COPI) vesicles, is an SMN-binding partner, implicating this protein complex in normal SMN function. To investigate the functional significance of the interaction between α-COP and SMN, we constructed an inducible NSC-34 cell culture system to model the consequences of SMN depletion and find that depletion of SMN protein results in shortened neurites. Heterologous expression of human SMN, and interestingly over-expression of α-COP, restores normal neurite length and morphology. Mutagenesis of the canonical COPI dilysine motifs in exon 2b results in failure to bind to α-COP and abrogates the ability of human SMN to restore neurite outgrowth in SMN-depleted motor neuron-like NSC-34 cells. We conclude that the interaction between SMN and α-COP serves an important function in the growth and maintenance of motor neuron processes and may play a significant role in the pathogenesis of SMA.

An early onset progressive motor neuron disorder in Scyl1-deficient mice is associated with mislocalization of TDP-43

The molecular and cellular bases of motor neuron diseases (MNDs) are still poorly understood. The diseases are mostly sporadic, with ~10% of cases being familial. In most cases of familial motor neuronopathy, the disease is caused by either gain-of-adverse-effect mutations or partial loss-of-function mutations in ubiquitously expressed genes that serve essential cellular functions. Here we show that deletion of Scyl1, an evolutionarily conserved and ubiquitously expressed gene encoding the COPI-associated protein pseudokinase SCYL1, causes an early onset progressive MND with characteristic features of amyotrophic lateral sclerosis (ALS). Skeletal muscles of Scyl1(-/-) mice displayed neurogenic atrophy, fiber type switching, and disuse atrophy. Peripheral nerves showed axonal degeneration. Loss of lower motor neurons (LMNs) and large-caliber axons was conspicuous in Scyl1(-/-) animals. Signs of neuroinflammation were seen throughout the CNS, most notably in the ventral horn of the spinal cord. Neural-specific, but not skeletal muscle-specific, deletion of Scyl1 was sufficient to cause motor dysfunction, indicating that SCYL1 acts in a neural cell-autonomous manner to prevent LMN degeneration and motor functions. Remarkably, deletion of Scyl1 resulted in the mislocalization and accumulation of TDP-43 (TAR DNA-binding protein of 43 kDa) and ubiquilin 2 into cytoplasmic inclusions within LMNs, features characteristic of most familial and sporadic forms of ALS. Together, our results identify SCYL1 as a key regulator of motor neuron survival, and Scyl1(-/-) mice share pathological features with many human neurodegenerative conditions.

Fine mapping of a region of chromosome 11q23.3 reveals independent locus associated with risk of glioma

Background

A single nucleotide polymorphism (SNP) at locus 11q23.3 (rs498872) in the near 5′-UTR of the PHLDB1 gene was recently implicated as a risk factor for gliomas in a genome-wide association study, and this involvement was confirmed in three additional studies.

Methodology/Principal Findings

To identify possible causal variants in the region, the authors genotyped 15 tagging SNPs in the 200 kb genomic region at 11q23.3 locus in a Chinese Han population-based case-control study with 983 cases and 1024 controls. We found evidence for an association between two independent loci (both the PHLDB1 and the ACRN1 genes) and a predisposition for gliomas. Among the multiple significant SNPs in the PHLDB1 gene region, the rs17749 SNP was the most significant [P = 1.31×10⁻⁶ in a recessive genetic model]. Additionally, two novel SNPs (rs2236661 and rs494560) that were independent of rs17749 were significantly associated with glioma risk in a recessive genetic model [P = 1.31×10⁻⁵ and P = 3.32×10⁻⁵, respectively]. The second novel locus was within the ARCN1 gene, and it was associated with a significantly reduced risk for glioma.

Conclusions/Significance

Our data strongly support PHLDB1 as a susceptibility gene for glioma, also shedding light on a new potentially candidate gene, ARCN1.

COPI transport complexes bind to specific RNAs in neuronal cells

Our fundamental understanding of how several thousand diverse RNAs are recognized in the soma, sorted, packaged, transported and localized within the cell is fragmentary. The COPa and COPb proteins of the coatomer protein I (COPI) vesicle complex were reported to interact with specific RNAs and represent a candidate RNA sorting and transport system. To determine the RNA-binding profile of Golgi-derived COPI in neuronal cells, we performed formaldehyde-linked RNA immunoprecipitation, followed by high-throughput sequencing, a process we term FLRIP-Seq (FLRIP, formaldehyde-cross-linked immunoprecipitation). We demonstrate that COPa co-immunoprecipitates a specific set of RNAs that are enriched in G-quadruplex motifs and fragile X mental retardation protein-associated RNAs and that encode factors that predominantly localize to the plasma membrane and cytoskeleton and function within signaling pathways. These data support the novel function of COPI in inter-compartmental trafficking of RNA.

New insights into behaviour using mouse ENU mutagenesis

Identifying genes involved in behavioural disorders in man is a challenge as the cause is often multigenic and the phenotype is modulated by environmental cues. Mouse mutants are a valuable tool for identifying novel pathways underlying specific neurological phenotypes and exploring the influence both genetic and non-genetic factors. Many human variants causing behavioural disorders are not gene deletions but changes in levels of expression or activity of a gene product; consequently, large-scale mouse ENU mutagenesis has the advantage over the study of null mutants in that it generates a range of point mutations that frequently mirror the subtlety and heterogeneity of human genetic lesions. ENU mutants have provided novel and clinically relevant functional information on genes that influence many aspects of mammalian behaviour, from neuropsychiatric endophenotypes to circadian rhythms. This review will highlight some of the most important findings that have been made using this method in several key areas of neurological disease research.

COPII and COPI traffic at the ER-Golgi interface

Protein traffic is necessary to maintain homeostasis in all eukaryotic organisms. All newly synthesized secretory proteins destined to the secretory and endolysosmal systems are transported from the endoplasmic reticulum to the Golgi before delivery to their final destinations. Here, we describe the COPII and COPI coating machineries that generate carrier vesicles and the tethers and SNAREs that mediate COPII and COPI vesicle fusion at the ER-Golgi interface.