A missense mutation in human INSC causes peripheral neuropathy

PAR3/INSC/LGN form an evolutionarily conserved complex required for asymmetric cell division in the developing brain, but its post-developmental function and disease relevance in the peripheral nervous system (PNS) remains unknown. We mapped a new locus for axonal Charcot-Marie-Tooth disease (CMT2) and identified a missense mutation c.209 T > G (p.Met70Arg) in the INSC gene. Modeling the INSCM70R variant in Drosophila, we showed that it caused proprioceptive defects in adult flies, leading to gait defects resembling those in CMT2 patients. Cellularly, PAR3/INSC/LGN dysfunction caused tubulin aggregation and necrotic neurodegeneration, with microtubule-stabilizing agents rescuing both morphological and functional defects of the INSCM70R mutation in the PNS. Our findings underscore the critical role of the PAR3/INSC/LGN machinery in the adult PNS and highlight a potential therapeutic target for INSC-associated CMT2.

Mitochondrial Function and Parkinson's Disease: From the Perspective of the Electron Transport Chain

Parkinson’s disease (PD) is known as a mitochondrial disease. Some even regarded it specifically as a disorder of the complex I of the electron transport chain (ETC). The ETC is fundamental for mitochondrial energy production which is essential for neuronal health. In the past two decades, more than 20 PD-associated genes have been identified. Some are directly involved in mitochondrial functions, such as PRKN, PINK1, and DJ-1. While other PD-associate genes, such as LRRK2, SNCA, and GBA1, regulate lysosomal functions, lipid metabolism, or protein aggregation, some have been shown to indirectly affect the electron transport chain. The recent identification of CHCHD2 and UQCRC1 that are critical for functions of complex IV and complex III, respectively, provide direct evidence that PD is more than just a complex I disorder. Like UQCRC1 in preventing cytochrome c from release, functions of ETC proteins beyond oxidative phosphorylation might also contribute to the pathogenesis of PD.

Dihydroceramide desaturase promotes the formation of intraluminal vesicles and inhibits autophagy to increase exosome production

Exosomes are important for cell–cell communication. Deficiencies in the human dihydroceramide desaturase gene, DEGS1, increase the dihydroceramide-to-ceramide ratio and cause hypomyelinating leukodystrophy. However, the disease mechanism remains unknown. Here, we developed an in vivo assay with spatially controlled expression of exosome markers in Drosophila eye imaginal discs and showed that the level and activity of the DEGS1 ortholog, Ifc, correlated with exosome production. Knocking out ifc decreased the density of the exosome precursor intraluminal vesicles (ILVs) in the multivesicular endosomes (MVEs) and reduced the number of exosomes released. While ifc overexpression and autophagy inhibition both enhanced exosome production, combining the two had no additive effect. Moreover, DEGS1 activity was sufficient to drive ILV formation in vitro. Together, DEGS1/Ifc controls the dihydroceramide-to-ceramide ratio and enhances exosome secretion by promoting ILV formation and preventing the autophagic degradation of MVEs. These findings provide a potential cause for the neuropathy associated with DEGS1-deficient mutations.

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An in vivo system was developed for observing exosome production in Drosophila

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Dihydroceramide desaturase (DEGS1/Ifc) promotes exosome production at two steps

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DEGS1/Ifc drives membrane invagination for the formation of intraluminal vesicles

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DEGS1/Ifc inhibits autophagic degradation of MVEs and increases exosome release

Drosophila as a model to study autophagy in neurodegenerative diseases and digestive tract

Autophagy regulates cellular homeostasis by degrading and recycling cytosolic components and damaged organelles. Disruption of autophagic flux has been shown to induce or facilitate neurodegeneration and accumulation of autophagic vesicles is overt in neurodegenerative diseases. The fruit fly Drosophila has been used as a model system to identify new factors that regulate physiology and disease. Here we provide a historical perspective of how the fly models have offered mechanistic evidence to understand the role of autophagy in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Charcot-Marie-Tooth neuropathy, and polyglutamine disorders. Autophagy also plays a pivotal role in maintaining tissue homeostasis and protecting organism health. The gastrointestinal tract regulates organism health by modulating food intake, energy balance, and immunity. Growing evidence is strengthening the link between autophagy and digestive tract health in recent years. Here, we also discuss how the fly models have advanced the understanding of digestive physiology regulated by autophagy.

Dihydroceramide desaturase regulates the compartmentalization of Rac1 for neuronal oxidative stress

Disruption of sphingolipid homeostasis is known to cause neurological disorders, but the mechanisms by which specific sphingolipid species modulate pathogenesis remain unclear. The last step of de novo sphingolipid synthesis is the conversion of dihydroceramide to ceramide by dihydroceramide desaturase (human DEGS1; Drosophila Ifc). Loss of ifc leads to dihydroceramide accumulation, oxidative stress, and photoreceptor degeneration, whereas human DEGS1 variants are associated with leukodystrophy and neuropathy. In this work, we demonstrate that DEGS1/ifc regulates Rac1 compartmentalization in neuronal cells and that dihydroceramide alters the association of active Rac1 with organelle-mimicking membranes. We further identify the Rac1-NADPH oxidase (NOX) complex as the major cause of reactive oxygen species (ROS) accumulation in ifc-knockout (ifc-KO) photoreceptors and in SH-SY5Y cells with the leukodystrophy-associated DEGS1^H132R variant. Suppression of Rac1-NOX activity rescues degeneration of ifc-KO photoreceptors and ameliorates oxidative stress in DEGS1^H132R-carrying cells. Therefore, we conclude that DEGS1/ifc deficiency causes dihydroceramide accumulation, resulting in Rac1 mislocalization and NOX-dependent neurodegeneration.

Systematic functional analysis of rab GTPases reveals limits of neuronal robustness to environmental challenges in flies

Rab GTPases are molecular switches that regulate membrane trafficking in all cells. Neurons have particular demands on membrane trafficking and express numerous Rab GTPases of unknown function. Here, we report the generation and characterization of molecularly defined null mutants for all 26 rab genes in Drosophila. In flies, all rab genes are expressed in the nervous system where at least half exhibit particularly high levels compared to other tissues. Surprisingly, loss of any of these 13 nervous system-enriched Rabs yielded viable and fertile flies without obvious morphological defects. However, all 13 mutants differentially affected development when challenged with different temperatures, or neuronal function when challenged with continuous stimulation. We identified a synaptic maintenance defect following continuous stimulation for six mutants, including an autophagy-independent role of rab26. The complete mutant collection generated in this study provides a basis for further comprehensive studies of Rab GTPases during development and function in vivo.

Mitochondrial UQCRC1 mutations cause autosomal dominant parkinsonism with polyneuropathy

Parkinson's disease is a neurodegenerative disorder with a multifactorial aetiology. Nevertheless, the genetic predisposition in many families with multi-incidence disease remains unknown. This study aimed to identify novel genes that cause familial Parkinson's disease. Whole exome sequencing was performed in three affected members of the index family with a late-onset autosomal-dominant parkinsonism and polyneuropathy. We identified a novel heterozygous substitution c.941A>C (p.Tyr314Ser) in the mitochondrial ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) gene, which co-segregates with disease within the family. Additional analysis of 699 unrelated Parkinson's disease probands with autosomal-dominant Parkinson's disease and 1934 patients with sporadic Parkinson's disease revealed another two variants in UQCRC1 in the probands with familial Parkinson's disease, c.931A>C (p.Ile311Leu) and an allele with concomitant splicing mutation (c.70-1G>A) and a frameshift insertion (c.73_74insG, p.Ala25Glyfs*27). All substitutions were absent in 1077 controls and the Taiwan Biobank exome database from healthy participants (n = 1517 exomes). We then assayed the pathogenicity of the identified rare variants using CRISPR/Cas9-based knock-in human dopaminergic SH-SY5Y cell lines, Drosophila and mouse models. Mutant UQCRC1 expression leads to neurite degeneration and mitochondrial respiratory chain dysfunction in SH-SY5Y cells. UQCRC1 p.Tyr314Ser knock-in Drosophila and mouse models exhibit age-dependent locomotor defects, dopaminergic neuronal loss, peripheral neuropathy, impaired respiratory chain complex III activity and aberrant mitochondrial ultrastructures in nigral neurons. Furthermore, intraperitoneal injection of levodopa could significantly improve the motor dysfunction in UQCRC1 p.Tyr314Ser mutant knock-in mice. Taken together, our in vitro and in vivo studies support the functional pathogenicity of rare UQCRC1 variants in familial parkinsonism. Our findings expand an additional link of mitochondrial complex III dysfunction in Parkinson's disease.

Loss of the Drosophila branched-chain α-ketoacid dehydrogenase complex results in neuronal dysfunction

Maple syrup urine disease (MSUD) is an inherited error in the metabolism of branched-chain amino acids (BCAAs) caused by a severe deficiency of the branched-chain α-ketoacid dehydrogenase (BCKDH) complex, which ultimately leads to neurological disorders. The limited therapies, including protein-restricted diets and liver transplants, are not as effective as they could be for the treatment of MSUD due to the current lack of molecular insights into the disease pathogenesis. To address this issue, we developed a Drosophila model of MSUD by knocking out the dDBT gene, an ortholog of the human gene encoding the dihydrolipoamide branched chain transacylase (DBT) subunit of BCKDH. The homozygous dDBT mutant larvae recapitulate an array of MSUD phenotypes, including aberrant BCAA accumulation, developmental defects, poor mobile behavior and disrupted L-glutamate homeostasis. Moreover, the dDBT mutation causes neuronal apoptosis during the developmental progression of larval brains. The genetic and functional evidence generated by in vivo depletion of dDBT expression in the eye indicates severe impairment of retinal rhabdomeres. Further, the dDBT mutant shows elevated oxidative stress and higher lipid peroxidation accumulation in the larval brain. Therefore, we conclude from in vivo evidence that the loss of dDBT results in oxidative brain damage that may lead to neuronal cell death and contribute to aspects of MSUD pathology. Importantly, when the dDBT mutants were administrated with Metformin, the aberrances in BCAA levels and motor behavior were ameliorated. This intriguing outcome strongly merits the use of the dDBT mutant as a platform for developing MSUD therapies.This article has an associated First Person interview with the joint first authors of the paper.

Alexithymia predicts poorer social and everyday functioning in schizophrenia and bipolar disorder

Alexithymia, or the inability to identify and describe one's emotions, is significantly higher in bipolar disorder (BD) and schizophrenia (SZ), compared to healthy controls (HC). Alexithymia has also been observed to predict psychosocial functioning in SZ. We investigated whether alexithymia predicted social and everyday functioning in BD, as well as transdiagnostically in HC, BD, and SZ patients. 56 BD, 45 SZ, and 50 HC were administered and compared on tests measuring neurocognition, social cognition, functioning and alexithymia. We conducted linear regressions assessing whether alexithymia predicted functional outcomes in BD. Next, we conducted hierarchical stepwise linear regressions investigating the predictive ability of neurocognition, social cognition and alexithymia on everyday and social functioning in our overall sample. BD and SZ patients were comparable on most demographics and demonstrated higher alexithymia compared to HCs. In BD, alexithymia predicted social functioning only. In the overall sample, difficulty identifying and describing feelings predicted everyday functioning; difficulty describing feelings predicted social functioning. Results suggest that aspects of alexithymia significantly predict functioning among these psychiatric groups, above and beyond the contributions of previously identified factors such as neurocognition and social cognition. Results may aid in developing proper interventions aimed at improving patients' ability to articulate their feelings.

Differential protective effects of connective tissue growth factor against Aβ neurotoxicity on neurons and glia

Impaired clearance of amyloid-β peptide (Aβ) leads to abnormal extracellular accumulation of this neurotoxic protein that drives neurodegeneration in sporadic Alzheimer's disease (AD). Connective tissue growth factor (CTGF/CCN2) expression is elevated in plaque-surrounding astrocytes in AD patients. However, the role of CTGF in AD pathogenesis remains unclear. Here we characterized the neuroprotective activity of CTGF. We found that CTGF facilitated Aβ uptake and subsequent degradation within primary glia and neuroblastoma cells. CTGF enhanced extracellular Aβ degradation via membrane-bound matrix metalloproteinase-14 (MMP14) in glia and extracellular MMP13 in neurons. In the brain of a Drosophila AD model, glial-expression of CTGF reduced Aβ deposits, improved locomotor function, and rescued memory deficits. Neuroprotective potential of CTGF against Aβ42-induced photoreceptor degeneration was disrupted through silencing MMPs. Therefore, CTGF may represent a node for potential AD therapeutics as it intervenes in glia-neuron communication via specific MMPs to alleviate Aβ neurotoxicity in the central nervous system.

Inguinal Hernia Mimicking as a Spigelian Hernia

Inguinal hernia is a common surgical condition requiring surgical intervention. The usual clinical presentation is a supra-inguinal swelling with the neck just above and medial to pubic tubercle. We report a case of inguinal hernia in an old lady that presented as an abdominal wall swelling, clinically suggestive of a Spigelian hernia.

A Retrospective Study of Seclusion in an Emergency Department

Objectives

To study the practice of seclusion in an emergency department (ED) and to explore high-risk elements during seclusion.

Methods

The study consisted of two parts: an in-depth analysis on all incidents associated with seclusion in a six-year period (1998–2004) and a two-year (2002–2004) retrospective analysis of secluded patient records to understand the rationale and patient outcome.

Results

Part 1: A total of 9 incident records were collected. Four patients were related to setting fire. Five patients had violence or threat of violence. The median length of stay (LOS) in seclusion at the time of incident was 129 minutes. Although 66.7% of the patients had additional restraint prior to the seclusion, incidents still occurred. Two staff sustained injuries and hospital facilities were damaged in some of the incidents. Six patients were later admitted to psychiatric hospital. Part 2: 141 patient data were collected in the study (M: 89 and F: 52). The average monthly number of patients secluded was about 6. The mean age was 45 years (SD 19) and the mean LOS was 616 minutes (SD 478). There were three incidences (2.1%) during the two-year period. A total of 82 patients (58.2%) were associated with violence or threat of violence and 38 (46.3%) of the group had psychiatric illness; and 50 patients (35.5%) were associated with alcohol or drug intoxication. Ultimately, 56 patients (39.7%) were admitted to psychiatric hospital and 64 patients (45.4%) were treated and discharged from the ED.

Conclusion

Seclusion is a high-risk practice. In our department, the most frequent indication was violence (58.2%), with nearly half of them having history of psychiatric illness. Psychiatric illness had the highest risk for incidents, especially those with violence or threat of violence. The LOS in seclusion was relatively long in the ED and might be one of the risk factors for incidents. Inadequate removal of potentially dangerous belongings from patients before seclusion may end up with catastrophic outcomes. Curiously, ED nurses are not allowed to search patients before seclusion. They are exposed to legal liability in exercising restraint and in searching for potentially dangerous items from patients. It is suggested that clear protocols and quality assurance programs should be instituted to ensure safe seclusion.

Reliability and Validity of the “Extended - Hurt, Insult, Threaten, Scream” (E-Hits) Screening Tool in Detecting Intimate Partner Violence in Hospital Emergency Departments in Hong Kong

Objectives

To assess the reliability and validity of a brief screening instrument, “E-HITS” (Extended - Hurt, Insult, Threaten, Scream), for detecting female intimate partner violence (IPV) in Hong Kong emergency departments (EDs).

Method

Quantitative data were collected from a victim group (n=110) and a control group (n=116). Statistical properties of the instruments were analysed to ascertain its internal consistency, test/re-test reliability, concurrent validity and discriminant validity.

Results

Cronbach's alpha was 0.90 for the E-HITS. Two-week test/re-test reliability was 0.71 (p<0.001). Respondents' scores on the E-HITS positively correlated with those on psychological aggression, physical assault, sexual coercion and injury scales, and negatively correlated with the negotiation scale of the revised Conflict Tactics Scale at a statistically significant level. Subsequent Receiver Operating Characteristic (ROC) curve analysis revealed that E-HITS reached a sensitivity of 98.2% and a specificity of 94.8% at a cut-off of 8.5. The overall accuracy of the E-HITS indicated by the area under curve (AUC) in the ROC is 0.991.

Conclusion

These results show that the E-HITS has good internal consistency, test/re-test reliability, as well as concurrent and discriminant validity. The E-HITS is a valid and reliable tool for screening intimate partner violence in Hong Kong EDs.

Atg9 antagonizes TOR signaling to regulate intestinal cell growth and epithelial homeostasis in Drosophila

Autophagy is essential for maintaining cellular homeostasis and survival under various stress conditions. Autophagy-related gene 9 (Atg9) encodes a multipass transmembrane protein thought to act as a membrane carrier for forming autophagosomes. However, the molecular regulation and physiological importance of Atg9 in animal development remain largely unclear. Here, we generated Atg9 null mutant flies and found that loss of Atg9 led to shortened lifespan, locomotor defects, and increased susceptibility to stress. Atg9 loss also resulted in aberrant adult midgut morphology with dramatically enlarged enterocytes. Interestingly, inhibiting the TOR signaling pathway rescued the midgut defects of the Atg9 mutants. In addition, Atg9 interacted with PALS1-associated tight junction protein (Patj), which associates with TSC2 to regulate TOR activity. Depletion of Atg9 caused a marked decrease in TSC2 levels. Our findings revealed an antagonistic relationship between Atg9 and TOR signaling in the regulation of cell growth and tissue homeostasis.

A recurrent WARS mutation is a novel cause of autosomal dominant distal hereditary motor neuropathy

Distal hereditary motor neuropathy is a heterogeneous group of inherited neuropathies characterized by distal limb muscle weakness and atrophy. Although at least 15 genes have been implicated in distal hereditary motor neuropathy, the genetic causes remain elusive in many families. To identify an additional causal gene for distal hereditary motor neuropathy, we performed exome sequencing for two affected individuals and two unaffected members in a Taiwanese family with an autosomal dominant distal hereditary motor neuropathy in which mutations in common distal hereditary motor neuropathy-implicated genes had been excluded. The exome sequencing revealed a heterozygous mutation, c.770A > G (p.His257Arg), in the cytoplasmic tryptophanyl-tRNA synthetase (TrpRS) gene (WARS) that co-segregates with the neuropathy in the family. Further analyses of WARS in an additional 79 Taiwanese pedigrees with inherited neuropathies and 163 index cases from Australian, European, and Korean distal hereditary motor neuropathy families identified the same mutation in another Taiwanese distal hereditary motor neuropathy pedigree with different ancestries and one additional Belgian distal hereditary motor neuropathy family of Caucasian origin. Cell transfection studies demonstrated a dominant-negative effect of the p.His257Arg mutation on aminoacylation activity of TrpRS, which subsequently compromised protein synthesis and reduced cell viability. His257Arg TrpRS also inhibited neurite outgrowth and led to neurite degeneration in the neuronal cell lines and rat motor neurons. Further in vitro analyses showed that the WARS mutation could potentiate the angiostatic activities of TrpRS by enhancing its interaction with vascular endothelial-cadherin. Taken together, these findings establish WARS as a gene whose mutations may cause distal hereditary motor neuropathy and alter canonical and non-canonical functions of TrpRS.

Lipophagy prevents activity-dependent neurodegeneration due to dihydroceramide accumulation in vivo

Dihydroceramide desaturases are evolutionarily conserved enzymes that convert dihydroceramide (dhCer) to ceramide (Cer). While elevated Cer levels cause neurodegenerative diseases, the neuronal activity of its direct precursor, dhCer, remains unclear. We show that knockout of the fly dhCer desaturase gene, infertile crescent (ifc), results in larval lethality with increased dhCer and decreased Cer levels. Light stimulation leads to ROS increase and apoptotic cell death in ifc-KO photoreceptors, resulting in activity-dependent neurodegeneration. Lipid-containing Atg8/LC3-positive puncta accumulate in ifc-KO photoreceptors, suggesting lipophagy activation. Further enhancing lipophagy reduces lipid droplet accumulation and rescues ifc-KO defects, indicating that lipophagy plays a protective role. Reducing dhCer synthesis prevents photoreceptor degeneration and rescues ifc-KO lethality, while supplementing downstream sphingolipids does not. These results pinpoint that dhCer accumulation is responsible for ifc-KO defects. Human dhCer desaturase rescues ifc-KO larval lethality, and rapamycin reverses defects caused by dhCer accumulation in human neuroblastoma cells, suggesting evolutionarily conserved functions. This study demonstrates a novel requirement for dhCer desaturase in neuronal maintenance in vivo and shows that lipophagy activation prevents activity-dependent degeneration caused by dhCer accumulation.

Graphene-deposited photonic crystal fibers for continuous refractive index sensing applications

We present a pilot demonstration of an optical fiber based refractive index (RI) sensor involving the deposition of graphene onto the surface of a segment of a photonic crystal fiber (PCF) in a fiber-based Mach-Zehnder Interferometer (MZI). The fabrication process is relatively simple and only involves the fusion splicing of a PCF between two single mode fibers. The deposition process relies only on the cold transfer of graphene onto the PCF segment, without the need for further physical or chemical treatment. The graphene overlay modified the sensing scheme of the MZI RI sensor, allowing the sensor to overcome limitations to its detectable RI range due to free spectral range issues. This modification also allows for continuous measurements to be obtained without the need for reference values for the range of RIs studied and brings to light the potential for simultaneous dual parameter sensing. The sensor was able to achieve a RI sensitivity of 9.4 dB/RIU for the RIs of 1.33-1.38 and a sensitivity of 17.5 dB/RIU for the RIs of 1.38-1.43. It also displayed good repeatability and the results obtained were consistent with the modeling.

Strategies for gene disruption in Drosophila

Drosophila melanogaster has been a classic model organism for the studies of genetics. More than 15,000 Drosophila genes have been annotated since the entire genome was sequenced; however, many of them still lack functional characterization. Various gene-manipulating approaches in Drosophila have been developed for the function analysis of genes. Here, we summarize some representative strategies utilized for Drosophila gene targeting, from the unbiased ethyl methanesulfonate (EMS) mutagenesis and transposable element insertion, to insertional/replacement homologous recombination and site-specific nucleases such as the zinc-finger nuclease (ZFN), the transcription activator-like effector nuclease (TALEN) and the CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 system. Specifically, we evaluate the pros and cons of each technique in a historical perspective. This review discuss important factors that should be taken into consideration for the selection of a strategy that best fits the specific needs of a gene knockout project.

A validation study of the Hong Kong version of Montreal Cognitive Assessment (HK-MoCA) in Chinese older adults in Hong Kong

OBJECTIVE

To validate the Hong Kong version of Montreal Cognitive Assessment (HK-MoCA) in identification of mild cognitive impairment and dementia in Chinese older adults.

DESIGN

Cross-sectional study.

SETTING

Cognition clinic and memory clinic of a public hospital in Hong Kong.

PARTICIPANTS

A total of 272 participants (dementia, n=130; mild cognitive impairment, n=93; normal controls, n=49) aged 60 years or above were assessed using HK-MoCA. The HK-MoCA scores were validated against expert diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed) criteria for dementia and Petersen's criteria for mild cognitive impairment. Statistical analysis was performed using receiver operating characteristic curve and regression analyses. Additionally, comparison was made with the Cantonese version of Mini-Mental State Examination and Global Deterioration Scale.

RESULTS

The optimal cutoff score for the HK-MoCA to differentiate cognitive impaired persons (mild cognitive impairment and dementia) from normal controls was 21/22 after adjustment of education level, giving a sensitivity of 0.928, specificity of 0.735, and area under the curve of 0.920. Moreover, the cutoff to detect mild cognitive impairment was 21/22 with a sensitivity of 0.828, specificity of 0.735, and area under the curve of 0.847. Score of the Cantonese version of the Mini-Mental State Examination to detect mild cognitive impairment was 26/27 with a sensitivity of 0.785, specificity of 0.816, and area under the curve of 0.857. At the optimal cutoff of 18/19, HK-MoCA identified dementia from controls with a sensitivity of 0.923, specificity of 0.918, and area under the curve of 0.971.

CONCLUSION

The HK-MoCA is a useful cognitive screening instrument for use in Chinese older adults in Hong Kong. A score of less than 22 should prompt further diagnostic assessment. It has comparable sensitivity with the Cantonese version of Mini-Mental State Examination for detection of mild cognitive impairment. It is brief and feasible to conduct in the clinical setting, and can be completed in less than 15 minutes. Thus, HK-MoCA provides an attractive alternative screening instrument to Mini-Mental State Examination which has ceiling effect (ie may fail to detect mild/moderate cognitive impairment in people with high education level or premorbid intelligence) and needs to be purchased due to copyright issues.

Charcot-Marie-Tooth 2B mutations in rab7 cause dosage-dependent neurodegeneration due to partial loss of function

The small GTPase Rab7 is a key regulator of endosomal maturation in eukaryotic cells. Mutations in rab7 are thought to cause the dominant neuropathy Charcot-Marie-Tooth 2B (CMT2B) by a gain-of-function mechanism. Here we show that loss of rab7, but not overexpression of rab7 CMT2B mutants, causes adult-onset neurodegeneration in a Drosophila model. All CMT2B mutant proteins retain 10–50% function based on quantitative imaging, electrophysiology, and rescue experiments in sensory and motor neurons in vivo. Consequently, expression of CMT2B mutants at levels between 0.5 and 10-fold their endogenous levels fully rescues the neuropathy-like phenotypes of the rab7 mutant. Live imaging reveals that CMT2B proteins are inefficiently recruited to endosomes, but do not impair endosomal maturation. These findings are not consistent with a gain-of-function mechanism. Instead, they indicate a dosage-dependent sensitivity of neurons to rab7-dependent degradation. Our results suggest a therapeutic approach opposite to the currently proposed reduction of mutant protein function.

DOI:http://dx.doi.org/10.7554/eLife.01064.001

Charcot-Marie-Tooth disease is an inherited disorder of the nervous system with symptoms that typically begin in adolescence or early adulthood. The sensory and motor nerves gradually degenerate, causing muscles to waste away and leading to the loss of touch sensation across the body. One subtype of the disease—Charcot-Marie-Tooth 2B—is caused by mutations in a gene called rab7, which codes for a protein that helps to regulate the breakdown of waste proteins inside cells.

Charcot-Marie-Tooth 2B is described as a genetically dominant disorder because all patients have one wild type copy and one mutant copy of the rab7 gene. Overexpression of the mutant gene in cells grown in culture alters many of the signaling pathways inside the cells, but it is unclear whether these alterations cause the pathology seen in the disease.

Now, Cherry et al. have obtained new insights into the genetics of Charcot-Marie-Tooth 2B by creating the first animal model of the disorder. Fruit flies that did not have the rab7 gene in the light-sensitive sensory neurons in their eyes were used to compare normal and mutant cells. While the two cell types were initially similar, the mutant cells gradually degenerated in the adult animal. By contrast, cells that overexpressed a mutant form of the rab7 gene continued to function normally throughout adulthood. Moreover, when mutant Rab7 proteins were introduced into the cells that lacked the rab7 gene, the proteins restored the cells’ sensitivity to light. These results suggest that mutant Rab7 proteins do not cause degeneration; instead, it is the loss of normal Rab7 function that causes problems.

At present, most research into treatment is aimed at finding ways to reduce the activity of mutant Rab7 proteins. However, the work of Cherry et al. suggests that increasing the activity of normal Rab7 proteins—or increasing the activity of alternative pathways that degrade waste proteins—may help to restore nerve function in this, and possibly other, neurodegenerative diseases.

DOI:http://dx.doi.org/10.7554/eLife.01064.002

A rare case of primary malignant melanoma in an ileostomy

The vast majority of malignant melanomas occur in the skin. These are associated with sunlight exposure and thought to be due to ultraviolet radiation. Melanomas in rare instances (1.3-1.4 percent) may originate from extracutaneous tissues such as the leptomeninges.(1) They have also been reported arising from gastrointestinal, respiratory and genitourinary mucosa. Sunlight is not an aetiologic factor with mucosal melanomas. Herein, we report an extremely rare example of malignant melanoma arising from the mucocutaneous junction of an ileostomy. Only one such case has been reported in the literature.(2).

Synergism between corticosteroids and Rapamycin for the treatment of intraocular inflammation

The authors studied the combination effect of corticosteroids with the new immunosuppressant Rapamycin for the treatment of intraocular inflammation. A median-effect analysis, of the combined effect of Rapamycin and dexamethasone, was performed on the inhibition of lymphocyte proliferation in culture. The mathematical formulas allowed for the calculation of combination indices and dose-reduction factors. On the basis of these in-vitro results, treatment with reduced doses of drugs in combination was evaluated in the rat model of experimental autoimmune uveoretinitis. The results showed that Rapamycin and dexamethasone were synergistic over a wide concentration range. The calculated dose reduction factors indicated that an equivalent inhibition of lymphocyte proliferation was achieved with a combination of Rapamycin and dexamethasone reduced by 5-7 and 3-6 fold respectively, compared to the concentration required when each drug was used alone. In animals, there was a significant reduction of the incidence and severity of ocular inflammation with low doses of the drugs in combination. The authors conclude that the observed synergistic effect between Rapamycin and dexamethasone suggests that the use of this drug combination might be advantageous in the treatment of patients with severe uveitis.

Inflammatory cellular kinetics in sympathetic ophthalmia a study of 29 traumatized (exciting) eyes

An immunohistochemical study was conducted on 29 cases of sympathetic ophthalmia (SO). Monoclonal antibodies against T, B, NK cells, macrophages, and MHC class II antigen (HLA-DR) were used. The choroidal infiltrate in 20 eyes was predominantly T cell while B cell predominated in four cases. All eyes with a B cell predominance came from males. A predominance of B cells was correlated to a longer duration of the disease (> 9 months) and in eyes showing phthisical changes. There was no correlation between a predominance of B cells with age, race, corticosteroid treatment or histological type (typical or atypical). These findings suggest that, although SO is a T cell mediated disease, the predominance of B cells in some cases may represent the end stage of the disease process, or seems a secondary pathological process. The kinetic change in cell populations during the disease may have therapeutic implication.

Inhibition of cellular transfer of experimental autoimmune uveoretinitis by Rapamycin

The crucial role of CD4(+) T cells in mediating uveitis is well recognized. One treatment strategy of non-infectious uveitis therefore seeks to inhibit T cell function. For that purpose the authors have evaluated the efficacy of Rapamycin (RAPA), an inhibitor of lymphocyte response to growth factors. To reproduce as best as possible the immune system condition during active disease, the adoptive transfer of activated T cells was used to induce experimental autoimmune uveoretinitis (EAU). Treatment with RAPA was delivered by continuous intravenous infusion. The results showed a complete inhibition of EAU transfer at the RAPA dose of 0.1 mg/kg/day. They indicate that RAPA could be a useful immunosuppressant for uveitis therapy.

Combining recombineering and ends-out homologous recombination to systematically characterize Drosophila gene families: Rab GTPases as a case study

Evaluating how an individual gene contributes to a particular biological process benefits greatly from a comprehensive understanding of all members of its gene family. Such knowledge is ideally obtained using multicellular model organisms, which provide rapid and decisive platforms for determining gene function. We recently established a novel transgenesis platform in Drosophila to systematically knock out all members of the Rab small GTPase family of membrane regulators. This platform combines BAC transgenesis/recombineering with ends-out homologous recombinations and Gateway^TM technologies and provides a new rapid and scalable method that eases the manipulation of endogenous loci. This method not only allows for the generation of molecularly defined lesions, but also the precise replacement or tagging of genes in their endogenous loci. Using this method, we found that up to half of all Rab GTPases exhibit enriched expression at synapses in the nervous system. Here we provide critical details about the underlying recombineering and transgenesis method, new cassettes for tagging endogenous loci and information on important parameters that will allow Drosophila researchers to target members of other gene families.

Similarities of Drosophila rab GTPases based on expression profiling: completion and analysis of the rab-Gal4 kit

We recently generated rab-Gal4 lines for 25 of 29 predicted Drosophila rab GTPases. These lines provide tools for the expression of reporters, mutant rab variants or other genes, under control of the regulatory elements of individual rab loci. Here, we report the generation and characterization of the remaining four rab-Gal4 lines. Based on the completed 'rab-Gal4 kit' we performed a comparative analysis of the cellular and subcellular expression of all rab GTPases. This analysis includes the cellular expression patterns in characterized neuronal and non-neuronal cells and tissues, the subcellular localization of wild type, constitutively active and dominant negative rab GTPases and colocalization with known intracellular compartment markers. Our comparative analysis identifies all Rab GTPases that are expressed in the same cells and localize to the same intracellular compartments. Remarkably, similarities based on these criteria are typically not predicted by primary sequence homology. Hence, our findings provide an alternative basis to assess potential roles and redundancies based on expression in developing and adult cell types, compartment identity and subcellular localization.

The strength/weakness of the AJCC/UICC staging system (7th edition) for nasopharyngeal cancer and suggestions for future improvement

BACKGROUND AND PURPOSE

To evaluate the current AJCC/UICC staging system (7th edition) for nasopharyngeal carcinoma and to explore for future improvement.

MATERIALS AND METHODS

A total of 985 patients, initially staged with preceding 5-6th edition, were retrospectively re-staged with the 7th edition. All were assessed by magnetic resonance imaging, and all 945 non-disseminated patients were irradiated with conformal/intensity-modulated technique.

RESULTS

Staging factors by both the 5-6th edition and the 7th edition were strongly significance for important endpoints (p<0.001). Down-staging of the previous T2a to T1 and, stages IIA to I in the 7th edition was appropriate. However, the impacts on overall stage distribution and prognostication were minimal. Further down-staging of the current T2 to T1, N2 to N1, stages II to I, and merging of N3a and N3b, stages IVA and IVB were suggested. With the 7th edition, the 5-year disease-specific survival (DSS) was 100% for stage I, 95% for II, 90% for III, 67% for IVA, 68% for IVB and 18% for IVC. The corresponding DSS for the proposed stages I, II, III and IV were 95%, 86%, 67% and 18%, respectively.

CONCLUSIONS

The changes introduced in the 7th edition were appropriate, but the magnitude of improvement was minimal. With improving results by modern management, further simplification of the staging system is suggested. The proposed system could lead to more accurate prognostication, further validation is warranted.

Intracellular trafficking in Drosophila visual system development: a basis for pattern formation through simple mechanisms

Intracellular trafficking underlies cellular functions ranging from membrane remodeling to receptor activation. During multicellular organ development, these basic cell biological functions are required as both passive machinery and active signaling regulators. Exocytosis, endocytosis, and recycling of several key signaling receptors have long been known to actively regulate morphogenesis and pattern formation during Drosophila eye development. Hence, intracellular membrane trafficking not only sets the cell biological stage for receptor-mediated signaling but also actively controls signaling through spatiotemporally regulated receptor localization. In contrast to eye development, the role of intracellular trafficking for the establishment of the eye-to-brain connectivity map has only recently received more attention. It is still poorly understood how guidance receptors are spatiotemporally regulated to serve as meaningful synapse formation signals. Yet, the Drosophila visual system provides some of the most striking examples for the regulatory role of intracellular trafficking during multicellular organ development. In this review we will first highlight the experimental and conceptual advances that motivate the study of intracellular trafficking during Drosophila visual system development. We will then illuminate the development of the eye, the eye-to-brain connectivity map and the optic lobe from the perspective of cell biological dynamics. Finally, we provide a conceptual framework that seeks to explain how the interplay of simple genetically encoded intracellular trafficking events governs the seemingly complex cellular behaviors, which in turn determine the developmental product.

Systematic discovery of Rab GTPases with synaptic functions in Drosophila

BACKGROUND

Neurons require highly specialized intracellular membrane trafficking, especially at synapses. Rab GTPases are considered master regulators of membrane trafficking in all cells, and only very few Rabs have known neuron-specific functions. Here, we present the first systematic characterization of neuronal expression, subcellular localization, and function of Rab GTPases in an organism with a brain.

RESULTS

We report the surprising discovery that half of all Drosophila Rabs function specifically or predominantly in distinct subsets of neurons in the brain. Furthermore, functional profiling of the GTP/GDP-bound states reveals that these neuronal Rabs are almost exclusively active at synapses and the majority of these synaptic Rabs specifically mark synaptic recycling endosomal compartments. Our profiling strategy is based on Gal4 knockins in large genomic fragments that are additionally designed to generate mutants by ends-out homologous recombination. We generated 36 large genomic targeting vectors and transgenic rab-Gal4 fly strains for 25 rab genes. Proof-of-principle knockout of the synaptic rab27 reveals a sleep phenotype that matches its cell-specific expression.

CONCLUSIONS

Our findings suggest that up to half of all Drosophila Rabs exert specialized synaptic functions. The tools presented here allow systematic functional studies of these Rabs and provide a method that is applicable to any large gene family in Drosophila.

Impact of JAK2V617F mutation on thrombosis and myeloid transformation in essential thrombocythemia: a multivariate analysis by Cox regression in 141 patients

OBJECTIVE

To perform a multivariate analysis by Cox proportional hazard model of the impact of JAK2 V617F mutation on thrombosis and myeloid transformations in patients with essential thrombocythemia (ET).

PATIENTS AND METHODS

The clinicopathologic features and outcome of a cohort of Chinese ET patients were retrospectively reviewed. JAK2 V617F mutation was detected by allele-specific polymerase chain reaction. Potential risk factors including JAK2 V617F that might impact on thrombosis and outcome were studied by multivariate analysis with Cox proportional hazard model.

RESULTS

Of 141 patients studied, JAK2 V617F was found in 80 cases (57%). JAK2 V617F was positively correlated with hemoglobin and leukocyte count at diagnosis. Univariate analysis showed significant thrombotic risks to be JAK2 V617F (P=0.006), hemoglobin >13 g/dl (P=0.015), and age >55 years (P=0.011). However, in multivariate analysis, only age and hemoglobin were independent risk factors. JAK2 V617F was unrelated to survival or leukemic/myelofibrotic transformation.

CONCLUSION

In Chinese patients with ET, JAK2 V617F was positively associated with age, hemoglobin, and leukocyte count, but was not an independent risk for thrombosis.

Serrano (sano) functions with the planar cell polarity genes to control tracheal tube length

Epithelial tubes are the functional units of many organs, and proper tube geometry is crucial for organ function. Here, we characterize serrano (sano), a novel cytoplasmic protein that is apically enriched in several tube-forming epithelia in Drosophila, including the tracheal system. Loss of sano results in elongated tracheae, whereas Sano overexpression causes shortened tracheae with reduced apical boundaries. Sano overexpression during larval and pupal stages causes planar cell polarity (PCP) defects in several adult tissues. In Sano-overexpressing pupal wing cells, core PCP proteins are mislocalized and prehairs are misoriented; sano loss or overexpression in the eye disrupts ommatidial polarity and rotation. Importantly, Sano binds the PCP regulator Dishevelled (Dsh), and loss or ectopic expression of many known PCP proteins in the trachea gives rise to similar defects observed with loss or gain of sano, revealing a previously unrecognized role for PCP pathway components in tube size control.

Tubular organ formation is a ubiquitous process required to sustain life in multicellular organisms. In this study, we focused on the tracheal system of the fruit fly, Drosophila melanogaster, and identified Serrano (Sano) as a novel protein expressed in several embryonic tubular organs, including trachea. sano loss results in over-elongated trachea, whereas Sano overexpression causes shortened trachea, suggesting that sano is required for proper tracheal tube length. Interestingly, Sano overexpression results in typical planar cell polarity (PCP) defects in many adult tissues and pupal wing cells. The PCP pathway is highly conserved from flies to mammals and it has been known to control cell polarity within the plane of epithelial tissues. Importantly, we found that Sano binds Dishevelled (Dsh), a key PCP regulator, and loss or ectopic expression of many known PCP proteins in the trachea give rise to similar defects observed with loss or gain of sano, suggesting a new role for the PCP genes in tube length control. Interestingly, the changes in tube length and PCP defects in the wing were linked to changes in apical domain size, suggesting that Sano and the PCP components affect either membrane recycling and/or the linkage of the membrane to the cytoskeleton.

The association of clinical findings and exposure profiles with melamine associated nephrolithiasis

BACKGROUND

Little is known about the exposure profiles of melamine in children. We evaluated the association of clinical findings, exposure patterns and biomarkers with nephrolithiasis in children with potential exposure to melamine.

METHODS

A case-control study was conducted in children aged 0-16 years with potential exposure to contaminated dairy products. Cases were defined as nephrolithiasis detected by renal ultrasonography. On the basis of different brands of contaminated dairy products consumed, subjects were classified into high exposure, low exposure and control groups with estimated melamine exposure levels of higher than 2.5 ppm, 0.05-2.5 ppm and lower than detection limits <0.05 ppm. We measured urine melamine for those with nephrolithiasis and age-matched and gender-matched controls within the subset of the study population.

RESULTS

The duration of consumption of contaminated products was longer in children with nephrolithiasis in the high exposure group than in controls (median (IQR) 12.0 (3.3-24.0) vs 6.0 (4.0-7.0) months; p = 0.048). High melamine exposure levels were significantly associated with nephrolithiasis (OR 61.04 (95% CI 12.73 to 292.84)). The risk was found to increase with estimate melamine exposure levels (p for trend <0.001). Two among 10 affected subjects with nephrolithiasis showed elevated urine melamine levels. In comparison, levels of all 20 controls were lower than the detection limit.

CONCLUSIONS

The risk of melamine-associated nephrolithiasis was related to duration of consumption of contaminated products and estimated melamine exposure levels. Though urine melamine was not a sensitive test, it might serve as an exposure biomarker in melamine-associated nephrolithiasis.

Cellular and humoral immune parameters among patients with retinitis pigmentosa and other retinal disorders

Patients with retinitis pigmentosa, other retinal degenerations and a group of normal volunteers were included in a masked study designed to examine the existence of autoimmune reactions toward retinal antigens and the possible defect in lymphokine production (IL-1, IL-2 and gamma interferon). The results obtained did not show any specific anamnestic response to the retinal S-Ag nor any outstanding defect in gamma interferon production by the lymphocytes of patients with retinitis pigmentosa. It is suggested that a larger masked study be conducted as soon as possible in order to clarify these aspects of immune aberrations in patients with retinitis pigmentosa.

Arachnoiditis ossificans

Arachnoiditis ossificans is a rare type of chronic arachnoiditis characterised by the presence of calcification or ossification of the spinal arachnoid. There are a few reports of this condition in Japanese and western populations but no case has been reported in a Chinese population before. We describe a 35-year-old woman with typical findings of arachnoiditis ossificans. A brief review of the literature is also presented.

Experimental analysis of spectral characteristics of antiresonant guiding photonic crystal fibers

Both numerical and experimental analyses are carried out to investigate the spectral characteristics of antiresonant guiding photonic crystal fibers. The transmission minima were observed at the wavelengths where LP(ml) (m<or=4, l=1,2,3,(...)) modes of the high-index inclusions in the cladding are cut off. As the order of modes increases, the bandwidths of the corresponding stop bands gradually reduce.

Iron-generated hydroxyl radicals kill retinal cells in vivo: effect of ferulic acid

Siderosis bulbi is vision threatening. An investigation into its mechanisms and management is crucial. Experimental siderosis was established by intravitreous administration of an iron particle (chronic) or FeSO4 (acute). After siderosis, there was a significant dose-responsive reduction in eletroretinogram (a/b-wave) amplitude, and an increase in •OH level, greater when caused by 24 mM FeSO4 than that by 8 mM FeSO4. Furthermore, the FeSO4-induced oxidative stress was significantly blunted by 100 μM ferulic acid (FA). Siderosis also resulted in an excessive glutamate release, increased [Ca++]i, and enhanced superoxide dismutase immunoreactivity. The latter finding was consistent with the Western blot result. Obvious disorganization including loss of photoreceptor outer segments and cholinergic amacrines together with a wide-spreading ferric distribution across the retina was present, which were related to the eletro-retinographic and pathologic dysfunctions. Furthermore, b-wave reduction and amacrine damage were respectively, significantly, dose-dependently, and clearly ameliorated by FA. Thus, siderosis stimulates oxidative stress, and possibly, subsequent excitotoxicity, and calcium influx, which explains why the retina is impaired electro-physiologically and pathologically. Importantly, FA protects iron toxicity perhaps by acting as a free radical scavenger. This provides an approach to the study and treatment of the iron-related disorders such as retained intraocular iron and Alzheimer disease.

Drosophila Naked cuticle (Nkd) engages the nuclear import adaptor Importin-alpha3 to antagonize Wnt/beta-catenin signaling

Precise control of Wnt/beta-catenin signaling is critical for animal development, stem cell renewal, and prevention of disease. In the fruit fly Drosophila melanogaster, the naked cuticle (nkd) gene limits signaling by the Wnt ligand Wingless (Wg) during embryo segmentation. Nkd is an intracellular protein that is composed of separable membrane- and nuclear-localization sequences (NLS) as well as a conserved EF-hand motif that binds the Wnt receptor-associated scaffold protein Dishevelled (Dsh), but the mechanism by which Nkd inhibits Wnt signaling remains a mystery. Here we identify a second NLS in Nkd that is required for full activity and that binds to the canonical nuclear import adaptor Importin-alpha3. The Nkd NLS is similar to the Importin-alpha3-binding NLS in the Drosophila heat-shock transcription factor (dHSF), and each Importin-alpha3-binding NLS required intact basic residues in similar positions for nuclear import and protein function. Our results provide further support for the hypothesis that Nkd inhibits nuclear step(s) in Wnt/beta-catenin signaling and broaden our understanding of signaling pathways that engage the nuclear import machinery.

Cell-autonomous, myristyl-independent activity of the Drosophila Wnt/Wingless antagonist Naked cuticle (Nkd)

Robust animal development, tissue homeostasis, and stem cell renewal requires precise control of the Wnt/beta-catenin signaling axis. In the embryo of the fruit fly Drosophila melanogaster, the naked cuticle (nkd) gene attenuates signaling by the Wnt ligand Wingless (Wg) during segmentation. nkd mutants have been reported to exhibit abnormalities in wg transcription, Wg protein distribution and/or transport, and the intracellular response to Wg, but the relationship between each alteration and the molecular mechanism of Nkd action remains unclear. In addition, whether Nkd acts in a cell-autonomous or nonautonomous fashion in the embryo is not known. Mammalian Nkd homologs have N-terminal consensus sequences that direct the post-translational addition of a lipophilic myristoyl moiety, but fly and mosquito Nkd, while sharing N-terminal sequence homology, lack a myristoylation consensus sequence. Here we provide evidence that fly Nkd acts cell-autonomously in the embryo, with its N-terminus able to confer unique functional properties and membrane association that cannot be mimicked in vivo by heterologous myristoylation consensus sequences. In conjunction with our recent observation that Nkd requires nuclear localization for function, our data suggest that Nkd acts at more than one subcellular location within signal-receiving cells to attenuate Wg signaling.

Spontaneous intra-hepatic haemorrhage in a patient with fever of unknown origin

Polyarteritis nodosa is a systemic necrotising vasculitis that affects the small- and medium-sized arteries. Multifocal aneurysmal formation in the renal, hepatic, and mesenteric vasculature is a hallmark of this condition, and spontaneous aneurysmal rupture may occur, resulting in life-threatening haemorrhage. We describe a 42-year-old man who initially presented with fever of unknown origin. A diagnosis could not be reached at that time despite extensive investigations. The fever subsided spontaneously after 8 weeks, and the patient remained well for 6 years until he was admitted again for evaluation of fever. During his hospital stay, he developed a spontaneous massive intra-hepatic haemorrhage resulting in hepatic rupture and a haemoperitoneum. The bleeding was controlled at emergency laparotomy. An abdominal angiography demonstrated multiple microaneurysms in the hepatic and mesenteric arterial vasculature. The clinical findings suggested polyarteritis nodosa, and the source of bleeding was probably a ruptured intra-hepatic artery aneurysm.

Effect of liquid crystal alignment on bandgap formation in photonic bandgap fibers

A simple analytical model is proposed to study the formation of bandgaps in liquid crystal photonic bandgap fibers. The model shows good agreement with full-vectorial plane-wave simulations. Particularly, bandgap splitting is observed due to anisotropy. If the optic axis of the liquid crystal lies perpendicular to the fiber axis, splitting of the fundamental modes of E(x) and E(y) is also observed.

High-efficiency 1040 and 1078 nm laser emission of a Yb:Y2O3 ceramic laser with 976 nm diode pumping

We report a high-efficiency diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Pumped by a 976 nm laser diode bar and with an absorbed pump power of 2.8 W, cw output power of 1.74 W at 1078 nm, and 0.73 W at 1040 nm were obtained. The slope efficiency was measured to be 82.4% for the 1078 nm laser emission and 57.1% for the 1040 nm laser emission.