Functional Analysis of Missense Mutations in Kv8.2 Causing Cone Dystrophy with Supernormal Rod Electroretinogram

Mutations in KCNV2 have been proposed as the molecular basis for cone dystrophy with supernormal rod electroretinogram. KCNV2 codes for the modulatory voltage-gated potassium channel α-subunit, Kv8.2, which is incapable of forming functional channels on its own. Functional heteromeric channels are however formed with Kv2.1 in heterologous expression systems, with both α-subunit genes expressed in rod and cone photoreceptors. Of the 30 mutations identified in the KCNV2 gene, we have selected three missense mutations localized in the potassium channel pore and two missense mutations localized in the tetramerization domain for analysis. We characterized the differences between homomeric Kv2.1 and heteromeric Kv2.1/Kv8.2 channels and investigated the influence of the selected mutations on the function of heteromeric channels. We found that two pore mutations (W467G and G478R) led to the formation of nonconducting heteromeric Kv2.1/Kv8.2 channels, whereas the mutations localized in the tetramerization domain prevented heteromer generation and resulted in the formation of homomeric Kv2.1 channels only. Consequently, our study suggests the existence of two distinct molecular mechanisms involved in the disease pathology.     

Homocysteate-Evoked Release of Acetylcholine from the Rabbit Retina

Abstract: The cholinergic amacrine cells of the rabbit retina can be labeled with [³H]choline and the activity of the cholinergic population monitored by following the release of [³H]acetylcholine. It has been proposed that l -homocysteate may be the main endogenous transmitter released onto cholinergic amacrine cells by bipolar cells. Therefore, we have examined the effects of the isomers of homocysteate on the release of [³H]acetylcholine. In magnesium-free medium, d -homocysteate was slightly more potent than the l -isomer. The addition of magnesium, which blocks responses mediated by NMDA receptors, preferentially reduced but did not eliminate, the response to l -homocysteate. 2-Amino-7-phosphonoheptanoate, a potent NMDA antagonist, preferentially blocked l -homocysteate evoked responses. 6,7-Dinitroquinoxaline-2,3-dione, a potent kainate antagonist, preferentially blocked d -homocysteate-evoked responses. Therefore, in the rabbit retina, l -homocysteate is an NMDA-preferring agonist, whereas d -homocysteate is a kainate-preferring agonist. In addition, we found that l -homocysteate can activate the physiologically activated kainate receptor but only when used in millimolar concentrations and under conditions that minimize NMDA-receptor activation. However, the low potency of l -homocysteate combined with low affinity for the glutamate transporter, lack of immunocytochemical localization in bipolar cells, and low retinal content place serious limitations on the role of l -homocysteate at the bipolar-to-cholinergic amacrine cell synapse.     

Characterization of DNA polymerase I*, a form of DNA polymerase I found in Escherichia coli expressing SOS functions

DNA polymerase I* is a form of the DNA polymerase I isolated from Escherichia coli which are expressing recA/lexA (SOS) functions. Induction of recA or polA1 cells by nalidixic acid does not result in the appearance of pol I*, but lexA or recA mutants that are constitutive for SOS functions constitutively express pol I* and mutants which lack functional recA protein produce pol I* when they carry a lexA mutation which renders the lexA repressor inoperative. Pol I* has been induced by nalidixic acid in dinA, dinD, dinF, and umuC mutants. Polymerase I* has a lower affinity for single-stranded DNA-agarose than polymerase I and it sediments through sucrose gradients in a dispersed manner between 6.6-10.5 S, whereas polymerase I sediments at 5 S. Whereas pol I* migrates significantly faster than pol I in nondenaturing polyacrylamide gels, the active polypeptide of both forms migrates at the same rate in denaturing polyacrylamide gels. Compared with polymerase I, polymerase I* has an enhanced capacity to incorporate the adenine analog, 2-amino-purine, into activated salmon sperm DNA and a relatively low fidelity in replicating synthetic polydeoxyribonucleotides. Both the 3'----5' (proofreading) and 5'----3' (nick-translational) exonuclease activities of pol I* and pol I are indistinguishable. Estimates of processivity give a value of approximately 6 for both forms of the enzyme.     

An internal region of rpoB is required for autogenous translational regulation of the beta subunit of Escherichia coli RNA polymerase.

In order to delineate the region involved in feedback regulation of the RNA polymerase beta subunit (encoded by rpoB), a collection of rpoB-lacZ translational fusions with different endpoints both upstream and downstream of the rpoB start site was assembled on lambda phage vectors. The extent of translational repression of beta was monitored by measuring beta-galactosidase levels in monolysogens of the fusions under conditions of increased intracellular concentrations of beta and beta' achieved via the induction of rpoBC expression from a multicopy plasmid. A construct containing as little as 29 bp upstream of the start of rpoB exhibited repression of beta-galactosidase activity to the same extent as a construct encoding the full upstream region. A construct which carried only 70 bp of the rpoB structural gene exhibited very little repression, while constructs which carried 126 or 221 bp of rpoB exhibited approximately the same degree of repression as a construct which carried 403 bp. These data suggest that the sequences important for feedback regulation of beta translation extend more than 70 bp into rpoB but are completely contained within a region which spans the sequences from 29 bp upstream to 126 bp downstream of the translational start site.     

Lung hyperinflation and functional exercise capacity in patients with COPD – a three-year longitudinal study

Background

Lung hyperinflation contributes to dyspnea, morbidity and mortality in chronic obstructive pulmonary disease (COPD). The inspiratory-to-total lung capacity (IC/TLC) ratio is a measure of lung hyperinflation and is associated with exercise intolerance. However, knowledge of its effect on longitudinal change in the 6-min walk distance (6MWD) in patients with COPD is scarce. We aimed to study whether the IC/TLC ratio predicts longitudinal change in 6MWD in patients with COPD.

Methods

This prospective cohort study included 389 patients aged 40–75?years with clinically stable COPD in Global Initiative for Chronic Obstructive Lung Disease stages II-IV. The 6MWD was measured at baseline, and after one and 3 years. We performed generalized estimating equation regression analyses to examine predictors for longitudinal change in 6MWD. Predictors at baseline were: IC/TLC ratio, age, gender, pack years, fat mass index (FMI), fat-free mass index (FFMI), number of exacerbations within 12?months prior to inclusion, Charlson index for comorbidities, forced vital capacity (FVC), forced expiratory volume in 1?s (FEV₁), and light and hard self-reported physical activity.

Results

Reduced IC/TLC ratio (p?<?0.001) was a statistically significant predictor for decline in 6MWD. With a 0.1-unit decrease in baseline IC/TLC ratio, the annual decline in 6MWD was 12.7?m (p?<?0.001). Study participants with an IC/TLC ratio in the upper quartiles maintained their 6MWD from baseline to year 3, while it was significantly reduced for the patients with an IC/TLC ratio in the lower quartiles. Absence of light and hard physical activity, increased age and FMI, decreased FEV₁ and FVC, more frequent exacerbations and higher Charlson comorbidity index were also predictors for lower 6MWD at any given time, but did not predict higher rate of decline over the timespan of the study.

Conclusion

Our findings demonstrated that patients with less lung hyperinflation at baseline maintained their functional exercise capacity during the follow-up period, and that it was significantly reduced for patients with increased lung hyperinflation.

     

Domesticated Animal Biobanking: Land of Opportunity

In the past decade, biobanking has fuelled great scientific advances in the human medical sector. Well-established domesticated animal biobanks and integrated networks likewise harbour immense potential for great scientific advances with broad societal impacts, which are currently not being fully realised. Political and scientific leaders as well as journals and ethics committees should help to ensure that we are well equipped to meet future demands in livestock production, animal models, and veterinary care of companion animals.In the last decade, human biobanking has emerged as an important driver of scientific activities, and biobanks are indisputably an invaluable resource for all types of research aimed at improving public health. The combination of accessible and well-characterized biological samples of various types linked with a multitude of associated data is driving scientific discoveries at unprecedented speed and making previously unthinkable lines of research a reality [1,2].Unfortunately, biobanking of animal samples is by far less well-established. In March 2015, Nature published an article, titled “Inside the first pig biobank,” describing a newly established biobank of porcine samples to be used in studying human diabetes and hailing it as a pioneering effort in animal biobanking [3]. A PubMed search confirmed that in comparison to human biobanking there appears to be negligible activity in the animal biobanking sector. Searching titles, abstracts, and keywords with the search keys “biobank,” “biobanking,” “genebank,” and “gene bank” and limiting the results to publication dates in 2015, only 9 of 498 search results referred to animal biobanks (see S1 Data). This apparent lack of activity in the animal biobanking sector is also reflected in a 2015 editorial of Biopreservation and Biobanking, the official journal of the International Society for Biological and Environmental Repositories (ISBER), which caters to biobanks of any species. The authors conclude that even though there has been increasing participation from the non-human biobanking sector in the annual ISBER meetings, there is still a pronounced lack of submissions to the journal pertaining to non-human biobanking, and human biobanking issues continue to dominate ISBER activities [4]. The roadmap of the European Council’s European Strategy Forum on Research Infrastructures (ESFRI) reveals that there are projects under way involving human (Biobanking and BioMolecular Resources Research Infrastructure [BBMRI]), marine (European Marine Biological Resource Centre [EMBRC]), microbial (Microbial Resource Research Infrastructure [MIRRI]), and mouse model (Infrafrontier) biobanks, with general animal biobanks starkly missing on that list [5].Naturally, some non-human biobanks storing animal samples, amongst others, do exist. The most active are likely the natural history collections, because they have the intrinsic task to collect, catalogue, and store specimens. The Global Genome Biodiversity Network (GGBN), established in 2011, acts as an umbrella organisation for biodiversity repositories and aims to establish standards and best practices as well as increase sample accessibility through its data portal [6]. A search of the most common domesticated animal species (cattle, sheep, goat, pig, horse, chicken, and dog) yielded only 13 records in the GGBN member repositories.However, some domesticated animal biobanks and less formalized sample collections can be found. Their hosting institutions range from veterinary hospitals, zoos, breeding and diagnostics companies, national farm animal genetic resource gene banks, to research institutes and universities. Depending on their purpose, the stored types of samples vary greatly and range from healthy tissue samples, diseased pathogenic tissue samples, DNA, and RNA to reproductive materials. An example of a well-established physical non-human biobanking infrastructure serving a university is the Swedish University of Agricultural Sciences’ (SLU) Biobank (http://www.slu.se/slubiobank). This biobank also offers a data portal for increasing the visibility and accessibility of non-human sample collections no matter where they are stored. This data portal would be redundant if all samples, together with their associated data, were stored in established biobanks that ensured the visibility of their samples through a network such as GGBN. In contrast, the European Genebank Network for Animal Genetic Resources (EUGENA), coordinated by the European Regional Focal Point on Animal Genetic Resources (http://www.rfp-europe.org), is an emerging networking activity specifically targeting only national farm animal genetic resource collections [7]. These disparate examples demonstrate that there is a lack of a unified and generalized approach to sample collections in the domesticated animal sector.Nonetheless, there are numerous examples of how different disciplines and stakeholders, and ultimately the general public, have already benefitted from the availability of biobanked domesticated animal samples.Even though the pig biobank was commended as a pioneering effort [3], there are in fact a number of biobanks that accommodate animal models for the study of human disease. The domestic dog, for example, with its unique population history, breed structure, and hundreds of spontaneous genetic conditions has proven to be an excellent model for gene mapping in simple and complex disorders [8]. Targeted and effective breeding programs over the past 150 years have created hundreds of distinct breeds that form genetic isolates with reduced genetic heterogeneity. This simplifies genetic studies because fewer susceptibility loci with higher impact contribute to complex disease and allow genetic breakthroughs with smaller study cohorts as compared to the corresponding human conditions [9].The annotation of the canine genome facilitated a rapid evolution of genomic tools and development of several canine biobanks across the continents [10]. Collectively, these biobanks house hundreds of thousands of DNA samples and tissue specimens for hundreds of conditions with medical relevance to humans. Importantly, many canine biobanks maintain active collaborative networks with the breeder community and dog fanciers as well as veterinary clinics and hospitals for patient recruitment and health updates.Besides playing an instrumental role for human health, biobanked animal samples heavily impact developments in food production and the sustainable management of the world’s finite resources. Biobanks in animal breeding, often referred to as gene banks, were initially established with the advent of new reproductive techniques, such as artificial insemination, and typically stored semen and embryos. These biobanks recently played a critical role in the swift implementation of genomic selection, which uses genome-wide SNP markers to predict the genetic merit of breeding individuals [11,12]. The efficient use of genomic selection requires large reference panels of individuals whose genetic values are known with high confidence. In cattle breeding, these are bulls with large numbers of offspring with recorded performance data, such as milk yield. Genomic selection could only be implemented so swiftly and successfully because DNA or semen samples from a large number of bulls were available from cattle breeding company biobanks, and these samples could be linked to performance records of the respective bulls’ offspring. This technology was first adopted by the dairy industry and can potentially result in a 60%–120% increase in the rate of genetic gain. Together with advanced genotyping and reproductive technologies, genomic selection has the potential to increase genetic improvement both in often neglected traits, such as feed efficiency and fertility, and in traits that only recently have become of interest, such as methane output in ruminants or adaptation to climate change [12]. Improvements in these traits are of great interest for ensuring global food security and sustainable management of our limited resources. Without the availability of the gene bank samples, as well as associated performance data records, this transformation would have taken decades, if it had happened at all.Biobanks also play an integral part in worldwide conservation efforts to counteract the well-documented loss of genetic diversity in production animals [13,14]. Slowly, the general perception that these repositories are only to be used in emergencies and as a last resort is changing. In 2012, the USDA National Animal Germplasm Program, for example, harboured more than 700,000 gamete and tissue samples from over 18,000 animals representing more than 130 breeds. From this repository, samples from more than 3,300 animals had been requested and distributed for use in research and industry by 2012. The applications included quantitative trait locus (QTL) studies, assessment of genetic distances, cryobiology research, generation of an experimental research line, reduction of inbreeding, and re-introduction of genotypic combinations lost in current production populations [14]. Samples from rare and endangered breeds are also finding use in research and development of the leading breeding companies. For example, in the Netherlands, a consortium of university and dairy industry partners genotyped samples from rare local cattle breeds to gain insight into the genetic background of milk fatty acid composition. Genomic-assisted introgression could ultimately be used to introduce favourable alleles found in the rare breeds into more widely used breeds.Biobanked samples also played an important role in fighting a viral infection, infectious pancreatic necrosis (IPN), which is common in farmed fish. This virus can lead to rates of >90% mortality in farmed Atlantic salmon, which, therefore, poses a threat to animal welfare and aquaculture industries. In 2008, a major QTL for IPN-resistance was detected in Atlantic salmon. Already, a year later, AquaGen, which supplies about 55% of Atlantic salmon eggs used commercially in Norway, was employing marker-assisted selection to produce IPN-resistant fish. This swift implementation of the QTL in marker-assisted selection was only possible due to the availability of biobanked samples collected in a challenge test in 2005 [15].In addition to combatting disease in animals, biobanked domestic animal samples also play a crucial role in fighting emerging infectious diseases that are often zoonotic, meaning that they can be transmitted between vertebrate animals and humans. Having access to samples of species that act as reservoirs of a disease greatly facilitates the work of public health responders during infectious disease outbreaks [16]. In this context, the collection and traceable link of associated samples, such as parasites, pathogens, and other microbiota, to their parent sample becomes especially important.We are convinced that these examples leave no doubt that biobanked animal samples hold great potential both for advancing human and animal health and welfare as well as securing future food production. Furthermore, the recent advent of cost-efficient gene modification technologies [17] envisages many production, performance, and health applications in livestock and companion animals and further adds interest in animal biobanks.When examining the causes for the low levels of activity in large-scale domesticated animal biobanking, both in regard to the establishment or use of existing physical biobanking infrastructures as well as overarching data portals, a number of hypotheses come to mind. The industries connected to domesticated animal biobanking, such as livestock and companion animal production and veterinary care, are dwarfed by the healthcare industry, so monetary incentives would presumably play a much smaller role. Legislation may have acted as a driver in the formalization and shaping of biobanks and differential legislation regarding the handling, storage, and sharing of human versus animal biosamples, and associated data may thus have led to disparate developments. It is moreover conceivable that the community around domesticated animal biobanking is more fragmented and consists of more diverse stakeholders (academic, non-profit, industrial) than the human biobanking community, which could explain the absence of large-scale cooperative umbrella projects. Moreover, there may be greater difficulties in drafting material transfer agreements for reproductive materials than for other types of samples.We will only be able to exploit the full potential if we, in parallel with human and biodiversity biobanking, tackle the challenges of standardized sampling, processing, and storage, sample visibility and accessibility, standardized codes for diagnoses, collection and storage of associated data with the possibility for updates, as well as ethical and regulatory issues. Here, it is advisable that the domesticated animal sector ensures full compatibility with and relies on existing initiatives wherever feasible. Especially important in this context is to ensure a link between samples and associated phenomic and genomic data, such as derived sequence data. To achieve agreement on standards, both in terms of sample processing and storage and sample visibility and accessibility, actors from veterinary hospitals, zoos, breeding and diagnostics companies, national farm animal genetic resource gene banks, research institutes, universities, and policymakers need to join forces. This is where we momentarily see a lack of coordinated efforts.To respond to these challenges and to ensure that we are well equipped to meet future demands in livestock production, animal models, and veterinary care of companion animals, we propose that scientific and political leaders need to (i) acknowledge the inadequacy of the current situation, (ii) create opportunity and support for the establishment of an international research infrastructure for animal biobanking, and (iii) motivate academic and industrial stakeholders to develop and coordinate biobanks based on lessons learned from human and biodiversity biobanking.In Europe, the European Council’s ESFRI could play a leading role in the establishment of a domesticated animal biobanking network, including best practices, direly needed standards, and a common ontology. In a landscape analysis of European research infrastructures, the 2016 ESFRI roadmap acknowledges a gap in the agricultural and bio-economy sector and explicitly lists livestock facilities including gene banks [5]. While an increase in activities regarding biobanking of farm animal genetic resources is certainly relevant, we consider this not to be far-reaching enough. A step in the right direction would be to begin with compiling information on all existing animal biobanks, analogous to BBMRI’s catalogue for European human biobanks [18], which currently contains information on 340 biobanks (http://www.bbmriportal.eu/).Moreover, ethics committees should require the storage of samples and associated data in formalized biobanks for the approval of scientific experiments. Similarly, journals should apply the same standard to samples and associated data, as they currently apply to molecular data, in terms of storage in formalized repositories prior to publication.     

Serum Metabolomics Reveals Serotonin as a Predictor of Severe Dengue in the Early Phase of Dengue Fever

Effective triage of dengue patients early in the disease course for in- or out-patient management would be useful for optimal healthcare resource utilization while minimizing poor clinical outcome due to delayed intervention. Yet, early prognosis of severe dengue is hampered by the heterogeneity in clinical presentation and routine hematological and biochemical measurements in dengue patients that collectively correlates poorly with eventual clinical outcome. Herein, untargeted liquid-chromatography mass spectrometry metabolomics of serum from patients with dengue fever (DF) and dengue hemorrhagic fever (DHF) in the febrile phase (<96 h) was used to globally probe the serum metabolome to uncover early prognostic biomarkers of DHF. We identified 20 metabolites that are differentially enriched (p<0.05, fold change >1.5) in the serum, among which are two products of tryptophan metabolism–serotonin and kynurenine. Serotonin, involved in platelet aggregation and activation decreased significantly, whereas kynurenine, an immunomodulator, increased significantly in patients with DHF, consistent with thrombocytopenia and immunopathology in severe dengue. To sensitively and accurately evaluate serotonin levels as prognostic biomarkers, we implemented stable-isotope dilution mass spectrometry and used convalescence samples as their own controls. DHF serotonin was significantly 1.98 fold lower in febrile compared to convalescence phase, and significantly 1.76 fold lower compared to DF in the febrile phase of illness. Thus, serotonin alone provided good prognostic utility (Area Under Curve, AUC of serotonin = 0.8). Additionally, immune mediators associated with DHF may further increase the predictive ability than just serotonin alone. Nine cytokines, including IFN-γ, IL-1β, IL-4, IL-8, G-CSF, MIP-1β, FGF basic, TNFα and RANTES were significantly different between DF and DHF, among which IFN-γ ranked top by multivariate statistics. Combining serotonin and IFN-γ improved the prognosis performance (AUC = 0.92, sensitivity = 77.8%, specificity = 95.8%), suggesting this duplex panel as accurate metrics for the early prognosis of DHF.     

Identifying Adult Dengue Patients at Low Risk for Clinically Significant Bleeding

Background

Clinically significant bleeding is important for subsequent optimal case management in dengue patients, but most studies have focused on dengue severity as an outcome. Our study objective was to identify differences in admission parameters between patients who developed clinically significant bleeding and those that did not. We sought to develop a model for discriminating between these patients.

Methods

We conducted a retrospective study of 4,383 adults aged >18 years who were hospitalized with dengue infection at Tan Tock Seng Hospital, Singapore from 2005 to 2008. Patients were divided into those with clinically significant bleeding (n = 188), and those without (n = 4,195). Demographic, clinical, and laboratory variables on admission were compared between groups to determine factors associated with clinically significant bleeding during hospitalization.

Results

On admission, female gender (p<0.001); temperature >38°C (p<0.001); nausea/vomiting (p = 0.009) and abdominal pain/tenderness (p = 0.005); lower systolic blood pressure (p<0.001); higher pulse rate (p<0.001); increased absolute neutrophil count (ANC; p<0.001); reduced absolute lymphocyte count (ALC; p<0.001), haematocrit percentage (p<0.001) and platelet count (p = 0.04), and increased prothrombin time (p = 0.003) were significantly associated with clinically significant bleeding on univariate analysis. Multivariate analysis showed that independent variables in the final model were female gender (aOR 2.85; 95% CI: 1.9–4.33); temperature >38°C (aOR 1.81; 95% CI: 1.27–2.61), nausea/vomiting (aOR 1.39; 95% CI: 0.94–2.12), ANC (aOR 1.3; 95% CI: 1.15–1.46), ALC (aOR 0.4; 95% CI: 0.25–0.64), hematocrit percentage (aOR 0.96; 95% CI: 0.92–1.002) and platelet count (aOR 0.993; 95% CI: 0.988–0.998). At the cutoff of -3.919, the model achieved an AUC of 0.758 (sensitivity:0.87, specificity: 0.38, PPV: 0.06, NPV: 0.98).

Conclusion

Clinical risk factors associated with clinically significant bleeding were identified. This model may be useful to complement clinical judgement in triaging adult dengue patients given the dynamic nature of acute dengue, particularly in pre-identifying those less likely to develop clinically significant bleeding.