Functional analysis of missense variants in the TRESK (KCNK18) K+ channel

A loss of function mutation in the TRESK K2P potassium channel (KCNK18), has recently been linked with typical familial migraine with aura. We now report the functional characterisation of additional TRESK channel missense variants identified in unrelated patients. Several variants either had no apparent functional effect, or they caused a reduction in channel activity. However, the C110R variant was found to cause a complete loss of TRESK function, yet is present in both sporadic migraine and control cohorts, and no variation in KCNK18 copy number was found. Thus despite the previously identified association between loss of TRESK channel activity and migraine in a large multigenerational pedigree, this finding indicates that a single non-functional TRESK variant is not alone sufficient to cause typical migraine and highlights the genetic complexity of this disorder. Migraine is a common, disabling neurological disorder with a genetic, environmental and in some cases hormonal component. It is characterized by attacks of severe, usually unilateral and throbbing headache, can be accompanied by nausea, vomiting and photophobia and is clinically divided into two main subtypes, migraine with aura (MA) when a migraine is accompanied by transient and reversible focal neurological symptoms and migraine without aura (MO)1. The multifactorial and clinical heterogeneity of the disorder have considerably hindered the identification of common migraine susceptibility genes and most of our current understanding comes from the studies of familial hemiplegic migraine (FHM), a rare monogenic autosomal dominant form of MA2. So far, the three susceptibility genes that have been convincingly identified in FHM families all encode ion channels or transporters: CACNA1A encoding the α1 subunit of the Cav2.1 calcium channel3, SCN1A encoding the Nav1.1 sodium channel4 and ATP1A2 encoding the α2 subunit of the Na+/K+ pump5. It is believed that mutations in these genes may lead to increased efflux of glutamate and potassium in the synapse and thereby cause migraine by rendering the brain more susceptible to cortical spreading depression (CSD)6 which is thought to play a role in initiating a migraine attack7,8. However, these genes have not to date been implicated in common forms of migraine9. Nevertheless, current opinion suggests that typical migraine, like FHM, is also disorder of neuronal excitability, ion homeostasis and neurotransmitter release10,11,12. Mutations in the SLC4A4 gene encoding the sodium-bicarbonate cotransporter NBCe1, have recently been implicated in several different forms of migraine13, and a variety of genes involved in glutamate homeostasis (PGCP, MTDH14 and LRP115) and a cation channel (TRPM8)15 have also recently been implicated in migraine via genome-wide association studies. Ion channels are therefore highly likely to play an important role in the pathogenesis of typical migraine. TRESK (KCNK18), is a member of the two-pore domain (K2P) family of potassium channels involved in the control of cellular electrical excitability16. Regulation of TRESK activity by the calcium-dependent phosphatase calcineurin17, as well as its expression in dorsal root ganglia (DRG)18 and trigeminal ganglia (TG)19,20 has led to a proposed role for this channel in a variety of pain pathways. In a recent study, a frameshift mutation (F139Wfsx24) in TRESK was identified in a large multigenerational pedigree where it co-segregated perfectly with typical MA and a significant genome-wide linkage LOD score of 3.0. Furthermore, functional analysis revealed that this mutation caused a complete loss of TRESK function and that the truncated subunit was also capable of down regulating wild-type channel function. This therefore highlighted KCNK18 as potentially important candidate gene and suggested that TRESK dysfunction might play a possible role in the pathogenesis of familial migraine with visual aura20. Additional screening for KCNK18 mutations in unrelated sporadic migraine and control cohorts also identified a number of other missense variants; R10G, A34V, C110R, S231P and A233V20. The A233V variant was found only in the control cohort, whilst A34V was identified in a single Australian migraine proband for which family samples were not available, but it was not detected in controls. By contrast, the R10G, C110R, and S231P variants were found in both migraineurs and controls in both cohorts. In this study, we have investigated the functional effect of these variants to further probe the potential association of TRESK dysfunction with typical migraine.

Modeling the cumulative genetic risk for multiple sclerosis from genome-wide association data

Background: Multiple sclerosis (MS) is the most common cause of chronic neurologic disability beginning in early to middle adult life. Results from recent genome-wide association studies (GWAS) have substantially lengthened the list of disease loci and provide convincing evidence supporting a multifactorial and polygenic model of inheritance. Nevertheless, the knowledge of MS genetics remains incomplete, with many risk alleles still to be revealed. Methods: We used a discovery GWAS dataset (8,844 samples, 2,124 cases and 6,720 controls) and a multi-step logistic regression protocol to identify novel genetic associations. The emerging genetic profile included 350 independent markers and was used to calculate and estimate the cumulative genetic risk in an independent validation dataset (3,606 samples). Analysis of covariance (ANCOVA) was implemented to compare clinical characteristics of individuals with various degrees of genetic risk. Gene ontology and pathway enrichment analysis was done using the DAVID functional annotation tool, the GO Tree Machine, and the Pathway-Express profiling tool. Results: In the discovery dataset, the median cumulative genetic risk (P-Hat) was 0.903 and 0.007 in the case and control groups, respectively, together with 79.9% classification sensitivity and 95.8% specificity. The identified profile shows a significant enrichment of genes involved in the immune response, cell adhesion, cell communication/ signaling, nervous system development, and neuronal signaling, including ionotropic glutamate receptors, which have been implicated in the pathological mechanism driving neurodegeneration. In the validation dataset, the median cumulative genetic risk was 0.59 and 0.32 in the case and control groups, respectively, with classification sensitivity 62.3% and specificity 75.9%. No differences in disease progression or T2-lesion volumes were observed among four levels of predicted genetic risk groups (high, medium, low, misclassified). On the other hand, a significant difference (F = 2.75, P = 0.04) was detected for age of disease onset between the affected misclassified as controls (mean = 36 years) and the other three groups (high, 33.5 years; medium, 33.4 years; low, 33.1 years). Conclusions: The results are consistent with the polygenic model of inheritance. The cumulative genetic risk established using currently available genome-wide association data provides important insights into disease heterogeneity and completeness of current knowledge in MS genetics.

Semaphorin–plexin signalling genes associated with human breast tumourigenesis

Introduction Gene expression profiling has enabled us to demonstrate the heterogeneity of breast cancers. The potential of a tumour to grow and metastasise is partly dependant on its ability to initiate angiogenesis or growth and remodelling of new blood vessels, usually from a pre-existing vascular network, to ensure delivery of oxygen, nutrients, and growth factors to rapidly dividing transformed cells along with access to the systemic circulation. Cell–cell signalling of semaphorin ligands through interaction with their plexin receptors is important for the homeostasis and morphogenesis of many tissues and has been widely studied for a role in neural connectivity, cancer, cell migration and immune responses. This study investigated the role of four semaphorin/plexin signalling genes in human breast cancers in vivo and in vitro. Materials and methods mRNA was extracted from formalin fixed paraffin embedded archival breast invasive ductal carcinoma tissue samples of progressive grades (grades I–III) and compared to tissue from benign tumours. Gene expression profiles were determined by microarray using the Affymetrix GeneChip® Human Genome U133 Plus 2.0 Arrays and validated by Q-PCR using a Corbett RotorGene 6000. Following validation, the gene expression profile of the identified targets was correlated with those of the human breast cancer cell lines MCF-7 and MDA-MD-231. Results The array data revealed that 888 genes were found to be significantly (p ≤ 0.05) differentially expressed between grades I and II tumours and 563 genes between grade III and benign tumours. From these genes, we identified four genes involved in semaphorin–plexin signalling including SEMA4D which has previously been identified as being involved in increased angiogenesis in breast cancers, and three other genes, SEMA4F, PLXNA2 and PLXNA3, which in the literature were associated with tumourigenesis, but not directly in breast tumourigenesis. The microarray analysis revealed that SEMA4D was significantly (P = 0.0347) down-regulated in the grade III tumours compared to benign tumours; SEMA4F, was significantly (P = 0.0159) down-regulated between grades I and II tumours; PLXNA2 was significantly (P = 0.036) down-regulated between grade III and benign tumours and PLXNA3 significantly (P = 0.042) up-regulated between grades I and II tumours. Gene expression of SEMA4D was validated using Q-PCR, demonstrating the same expression profile in both data sets. When the sample set was increased to incorporate more cases, SEMA4D continued to follow the same expression profile, including statistical significance for the differences observed and small standard deviations. In vitro the same pattern was present where expression for SEMA4D was significantly higher in MDA-MB-231 cells when compared to MCF-7 cells. The expression of SEMA4F, PLXNA2 and PLXNA3 could not be validated using Q-PCR, however in vitro analysis of these three genes revealed that both SEMA4F and PLXNA3 followed the microarray trend in expression, although they did not reach significance. In contrast, PLXNA2 demonstrated statistical significance and was in concordance with the literature. Discussion We, and others, have proposed SEMA4D to be a gene with a potentially protective effect in benign tumours that contributes to tumour growth and metastatic suppression. Previous data supports a role for SEMA4F as a tumour suppressor in the peripheral nervous system but our data seems to indicate that the gene is involved in tumour progression in breast cancer. Our in vitro analysis of PLXNA2 revealed that the gene has higher expression in more aggressive breast cancer cell types. Finally, our in vitro analysis on PLXNA3 also suggest that this gene may have some form of growth suppressive role in breast cancer, in addition to a similar role for the gene previously reported in ovarian cancer. From the data obtained in this study, SEMA4D may have a role in more aggressive and potentially metastatic breast tumours. Conclusions Semaphorins and their receptors, the plexins, have been implicated in numerous aspects of neural development, however their expression in many other epithelial tissues suggests that the semaphorin–plexin signalling system also contributes to blood vessel growth and development. These findings warrant further investigation of the role of semaphorins and plexins and their role in normal and tumour-induced angiogenesis in vivo and in vitro. This may represent a new front of attack in anti-angiogenic therapies of breast and other cancers.

Gene expression studies in multiple sclerosis

Multiple sclerosis (MS) is a serious neurological disorder affecting young Caucasian individuals, usually with an age of onset at 18 to 40 years old. Females account for approximately 60x of MS cases and the manifestation and course of the disease is highly variable from patient to patient. The disorder is characterised by the development of plaques within the central nervous system (CNS). Many gene expression studies have been undertaken to look at the specific patterns of gene transcript levels in MS. Human tissues and experimental mice were used in these gene-profiling studies and a very valuable and interesting set of data has resulted from these various expression studies. In general, genes showing variable expression include mainly immunological and inflammatory genes, stress and antioxidant genes, as well as metabolic and central nervous system markers. Of particular interest are a number of genes localised to susceptible loci previously shown to be in linkage with MS. However due to the clinical complexity of the disease, the heterogeneity of the tissues used in expression studies, as well as the variable DNA chips/membranes used for the gene profiling, it is difficult to interpret the available information. Although this information is essential for the understanding of the pathogenesis of MS, it is difficult to decipher and define the gene pathways involved in the disorder. Experiments in gene expression profiling in MS have been numerous and lists of candidates are now available for analysis. Researchers have investigated gene expression in peripheral mononuclear white blood cells (PBMCs), in MS animal models Experimental Allergic Encephalomyelitis (EAE) and post mortem MS brain tissues. This review will focus on the results of these studies.

Migraine genetics and prospects for pharmacotherapy

Migraine is a common complex neurological disorder with a well-known but poorly characterized genetic liability. The search for migraine susceptibility genes has been the focus of intense research. It is now believed that common migraine is not a single gene disorder, but attributable to several potentially interacting genetic variants. These variants may differ in each sufferer and interact with environmental factors to set the individual migraine threshold. This genetic liability may play an important role in the clinical heterogeneity seen in migraine and also in the variability of treatment response. This review will look at genetic loci implicated in migraine to date and consider their current or prospective role in migraine therapy. To elucidate the complex nature of migraine genetic liability, approaches that consider detailed endophenotypic profiles that encompass treatment response may provide much more relevant information than simple end diagnosis.

Minor head trauma – induced sporadic hemiplegic migraine coma

Familial hemiplegic migraine is a severe, rare subtype of migraine. Gene mutations on chromosome 19 have been identified in the calcium channel, voltage-dependent, P/Q type, alpha-1A subunit gene (chromosome 19p13) for familial hemiplegic migraine. Recently a gene mutation (Serine-218-Leucine) for a dramatic syndrome associated with familial hemiplegic migraine, commonly named “migraine coma”, has implicated exon 5 of this gene. The occurrence of trivial head trauma, in such familial hemiplegic migraine patients, may also be complicated by severe, sometimes even fatal, cerebral edema and coma occurring after a lucid interval. Sporadic hemiplegic migraine shares a similar spectrum of clinical presentation and genetic heterogeneity. The case report presented in this article implicates the involvement of the Serine-218-Leucine mutation in the extremely rare disorder of minor head trauma–induced migraine coma. We conclude that the Serine-218-Leucine mutation in the calcium channel, voltage-dependent, P/Q type, alpha-1A subunit gene is involved in sporadic hemiplegic migraine, delayed cerebral edema and coma after minor head trauma.

An analysis of clinical characteristics in genetically linked migraine-affected pedigrees

Migraine is a common complex disorder characterized by severe recurrent headache and usually accompanied by nausea and vomiting. Previous studies in our laboratory have utilized three large multigenerational Australian pedigrees affected with migraine to indicate that the disease is genetically heterogeneous, with linkage results implicating genomic susceptibility regions on both chromosomes 19p and Xq. The present study explores the possibility of a correlation between genetic and clinical heterogeneity in these affected pedigrees. Specifically, the clinical characteristics of migraine including subtype, age of onset, frequency, duration, and disease symptoms were compared between the migraine pedigrees, and gender differences were also assessed. Our exploratory analyses revealed no significant differences in any of the clinical characteristics tested between the chromosome 19-linked family and the two X-linked families. Also, we did not detect any differences in male vs. female clinical features for these pedigrees. In conclusion, migraine is considered to be a clinically and genetically heterogeneous disorder; however, our study provided no conclusive evidence that variation in genomic susceptibility region is related to heterogeneity at the clinical level in these migraine-affected pedigrees.

How distributional preferences shape incentives on (experimental) markets for credence goods

Credence goods markets suffer from inefficiencies caused by superior information of sellers about the surplus-maximizing quality. While standard theory predicts that equal mark-up prices solve the credence goods problem if customers can verify the quality received, experimental evidence indicates the opposite. We identify a lack of robustness of institutional design with respect to heterogeneity in distributional preferences as a possible cause and design new experiments that allow for parsimonious identification of sellers’ distributional types. Our results indicate that less than a fourth of the subjects behave according to standard theory’s assumption, the rest behaving either in line with non-standard selfish or in accordance with non-trivial other-regarding preferences. We discuss consequences of our findings for institutional design and agent selection.

Evidence for an X-linked genetic component in familial typical migraine

Migraine is a common complex disorder that shows strong familial aggregation. There is a general increased prevalence of migraine in females compared with males, with recent studies indicating that migraine affects 18% of females compared with 6% of males. This preponderance of females among migraine sufferers coupled with evidence of an increased risk of migraine in first degree relatives of male probands but not in relatives of female probands suggests the possibility of an X-linked dominant gene. We report here the localization of a typical migraine susceptibility locus to the X chromosome. Of three large multigenerational migraine pedigrees two families showed significant excess allele sharing to Xq markers (P = 0.031 and P = 0.012). Overall analysis of data from all three pedigrees gave significant evidence in support of linkage and heterogeneity (HLOD = 3.1). These findings provide conclusive evidence that familial typical migraine is a heterogeneous disorder. We suggest that the localization of a migraine susceptibility locus to the X chromosome could in part explain the increased risk of migraine in relatives of male probands and may be involved in the increased female prevalence of this disorder.

A systematic review of mathematical models of mosquito-borne pathogen transmission: 1970-2010

Mathematical models of mosquito-borne pathogen transmission originated in the early twentieth century to provide insights into how to most effectively combat malaria. The foundations of the Ross–Macdonald theory were established by 1970. Since then, there has been a growing interest in reducing the public health burden of mosquito-borne pathogens and an expanding use of models to guide their control. To assess how theory has changed to confront evolving public health challenges, we compiled a bibliography of 325 publications from 1970 through 2010 that included at least one mathematical model of mosquito-borne pathogen transmission and then used a 79-part questionnaire to classify each of 388 associated models according to its biological assumptions. As a composite measure to interpret the multidimensional results of our survey, we assigned a numerical value to each model that measured its similarity to 15 core assumptions of the Ross–Macdonald model. Although the analysis illustrated a growing acknowledgement of geographical, ecological and epidemiological complexities in modelling transmission, most models during the past 40 years closely resemble the Ross–Macdonald model. Modern theory would benefit from an expansion around the concepts of heterogeneous mosquito biting, poorly mixed mosquito-host encounters, spatial heterogeneity and temporal variation in the transmission process.

DNA probes in Charcot-Marie-Tooth neuropathy

Results of Duffy (Fy) linkage confirm genetic heterogeneity in Charcot-Marie-Tooth disease type 1 (CMT1). Of 11 families informative for Fy, four showed probable linkage with CMT1, seven showed probable non-linkage and two showed definite non-linkage. These results suggest that Fy linked CMT1 may be less common than previously thought. These results combined with those of another DNA probe for the antithrombin III gene confirm that there are at least two gene loci for CMT1, termed 1A and 1B.

Heritage language for Chinese Australians : negotiating 'Chineseness' and, capitalising on resources in the lived world

The ethnic identity and commitment of Heritage Language Learners play salient roles in Heritage Language learning process. The mutually constitutive effect amongst Heritage Language Learner's ethnic identity, commitment, and Heritage Language proficiency has been well documented in social psychological and poststructuralist literatures. Both social psychological and poststructural schools offer meaningful insights into particular contexts but receive critiques from other contexts. In addition, the two schools largely oppose each other. This study uses Bourdieu's sociological triad of habitus, capital, and field to reconcile the two schools through the examination of Chinese Heritage Language Learners in Australia, an idiosyncratic social, cultural, and historical context for these learners. Specifically, this study investigates how young Chinese Australian adults (18-35 in age) negotiate their 'Chineseness' and capitalise on resources through Chinese Heritage Language learning in the lived world. The study adopts an explanatory mixed methods design to combine the quantitative approach with the qualitative approach. The initial quantitative phase addresses the first research question: Is Chinese Heritage Language proficiency of young Chinese Australian adults influenced by their investment of capital, the strength of their habitus of 'Chineseness', or both? The subsequent qualitative phase addresses the second research question: How do young Chinese Australian adults understand their Chinese Heritage Language learning in relation to (potential) profits produced by this linguistic capital in given fields? The initial quantitative phase applies Structural Equation Modelling to analyse the data from an online survey with 230 respondents. Findings indicate the statistically significant positive contribution made by the habitus of 'Chineseness' and by investment of capital to Chinese Heritage Language proficiency (r = .71 and r = .86 respectively). Subsequent multiple regression analysis demonstrates that 62% of the variance of Chinese Heritage Language proficiency can be accounted for by the joint contribution of 'Chineseness' and 'capital'. The qualitative phase of the study uses multiple interviews with five participants. It reveals that Chinese Heritage Language offers meaningful benefits for participants in the forms of capital production and habitus capture or recapture. Findings from the two phases talk to each other in terms of the inherent entanglement amongst habitus of 'Chineseness', investment of capital, and Chinese Heritage Language proficiency. The study offers important contributions. Theoretically, by virtue of Bourdieu's signature concepts of habitus, capital, and field, the study provides answers to questions that both social psychological and poststructuralist theories have long been struggling to answer. Methodologically, the position of 'pluralism' talks back to Bourdieu's theory and forwards to the mixed methods design. Particularly, the study makes a methodological breakthrough: A set of instruments was developed and validated to quantify Bourdieu's key concepts of capital and habitus within certain social fields. Practically, understanding Chinese Australians' heterogeneity and the potential drivers behind Chinese Heritage Language learning contributes to the growing interest in Chinese Australians' contemporary life experiences and helps to better accommodate linguistically diverse Chinese Heritage Language Learners in Chinese language courses. In addition, this study is very timely. It resonates with the recently released Australia in the Asian Century White Paper: Chinese Australians, with sound knowledge of Chinese culture and language obtained through negotiating their 'Chineseness' and capitalising on diverse resources for learning, will help to serve Australia's economic, social, and political needs in unique ways.

Self management of haemodialysis for end stage renal disease : a systematic review

Background Exploring self management in End Stage Renal Disease is extremely important for patients as they encounter several challenges including ongoing symptoms, complex treatments and restrictions, uncertainty about life and a dependency on technology, all of which impact upon their autonomy particularly after commencement of haemodialysis. Objective To summarise the effects of nursing interventions which effect selfmanagement of haemodialysis for patients with End Stage Renal Disease. Search strategy Search terms were chosen after reviewing text words and MeSH terms in relevant articles and databases. An extensive search of the literature from 1966 to June 2009 was conducted across a range of health databases including Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, PsycINFO and Web of Science. Further studies were identified from reference lists of all retrieved studies. Selection criteria We considered randomised controlled trials that compared interventions to improve self management of haemodialysis in patients with ESRD. In the absence of RCTs, comparative studies without randomisation as well as before and after studies were considered for inclusion. Methodological quality Study reports selected for retrieval were assessed by two independent reviewers for methodological quality prior to inclusion in the review using the standardised critical appraisal instruments for the Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information package (SUMARI). Data collection and analysis Data was extracted using the JBI data extraction tool for evidence of effectiveness independently by pairs of review authors. The evidence was reported in narrative summaries due to heterogeneity of the interventions of the studies. Results and conclusions Five randomised controlled trials were included in the review. Overall, the evidence found that psychosocial and educational interventions influenced self management of haemodialysis in this patient population.

HLA-DRB1 associations with disease susceptibility and clinical course in Australians with multiple sclerosis

Human leucocyte antigen (HLA)-DRB1*1501 and other class II alleles influence susceptibility to multiple sclerosis (MS), but their contribution if any to the clinical course of MS remains uncertain. Here, we have investigated DRB1 alleles in a large sample of 1230 Australian MS cases, with some enrichment for subjects with primary progressive (PPMS) disease (n = 246) and 1210 healthy controls. Using logistic regression, we found that DRB1*1501 was strongly associated with risk (P = 7 x 10-45), as expected, and after adjusting for DRB1*1501, a predisposing effect was also observed for DRB1*03 (P = 5 x 10-7). Individuals homozygous for either DRB1*15 or DRB1*03 were considerably more at risk of MS than heterozygotes and non-carriers. Both the DRB1*04 and the DRB1*01/DRB1*15 genotype combination, respectively, protected against PPMS in comparison to subjects with relapsing disease. Together, these data provide further evidence of heterogeneity at the DRB1 locus and confirm the importance of HLA variants in the phenotypic expression of MS.

Prevalence, trends and associated socio-economic factors of obesity in South Asia

Aim Worldwide obesity levels have increased unprecedentedly over the past couple of decades. Although the prevalence, trends and associated socio-economic factors of the condition have been extensively reported in Western populations, less is known regarding South Asian populations. Methods A review of articles using Medline with combinations of the MeSH terms: 'Obesity', 'Overweight' and 'Abdominal Obesity' limiting to epidemiology and South Asian countries. Results Despite methodological heterogeneity and variation according to country, area of residence and gender , the most recent nationally representative and large regional data demonstrates that without any doubt there is a epidemic of obesity, overweight and abdominal obesity in South Asian countries. Prevalence estimates of overweight and obesity (based on Asian cut-offs: overweight ≥ 23 kg/m(2), obesity ≥ 25 kg/m(2)) ranged from 3.5% in rural Bangladesh to over 65% in the Maldives. Abdominal obesity was more prevalent than general obesity in both sexes in this ethnic group. Countries with the lowest prevalence had the highest upward trend of obesity. Socio-economic factors associated with greater obesity in the region included female gender, middle age, urban residence, higher educational and economic status. Conclusion South Asia is significantly affected by the obesity epidemic. Collaborative public health interventions to reverse these trends need to be mindful of many socio-economic constraints in order to provide long-term solutions.