Encapsulation of Caenorhabditis elegans in Water-in-Water Microdroplets to Study the Worm Viability: Alternative Avenue to Manipulate Microdroplet Environment.

Due to the great biocompatibility of the aqueous two phase system (ATPS), biological cells have been widely encapsulated in ATPS microdroplets (diameter < 50 µm). However, the immobilization of relatively large multicellular organisms such as Caenorhabditis elegans in ATPS droplets remains challenging as the spontaneous generation of droplets greater than 200 µm is difficult without external perturbations. In this study, we utilize a microneedle-assisted coflow microfludic channel to passively form ATPS microdroplets larger than 200 µm and successfully entrap C. elegans in the microdroplets. We monitor the worm viability and its temporal stroke frequency up to 6 h. We study the effects of dextran (DEX)-to-polyethylene glycol (PEG) flow ratios and worm concentration on the droplet diameter, worm encapsulation efficiency, and the number of droplets containing individual worms. Larger ATPS microdroplets (>200 µm) form in the ranges of capillary number (Ca) between 0.020 to 0.20 and Weber number (We) between 10-5 and 10-3. An ATPS with the encapsulation ability and biocompatibility can offer an alternative immobilization tool for multicellular organisms to existing platforms such as water/oil droplets.

Identification of enzymes that have helminth-specific active sites and are required for Rhodoquinone-dependent metabolism as targets for new anthelmintics.

Soil transmitted helminths (STHs) are major human pathogens that infect over a billion people. Resistance to current anthelmintics is rising and new drugs are needed. Here we combine multiple approaches to find druggable targets in the anaerobic metabolic pathways STHs need to survive in their mammalian host. These require rhodoquinone (RQ), an electron carrier used by STHs and not their hosts. We identified 25 genes predicted to act in RQ-dependent metabolism including sensing hypoxia and RQ synthesis and found 9 are required. Since all 9 have mammalian orthologues, we used comparative genomics and structural modeling to identify those with active sites that differ between host and parasite. Together, we found 4 genes that are required for RQ-dependent metabolism and have different active sites. Finding these high confidence targets can open up in silico screens to identify species selective inhibitors of these enzymes as new anthelmintics.

Alternative splicing of coq-2 controls the levels of rhodoquinone in animals.

Parasitic helminths use two benzoquinones as electron carriers in the electron transport chain. In normoxia, they use ubiquinone (UQ), but in anaerobic conditions inside the host, they require rhodoquinone (RQ) and greatly increase RQ levels. We previously showed the switch from UQ to RQ synthesis is driven by a change of substrates by the polyprenyltransferase COQ-2 (Del Borrello et al., 2019; Roberts Buceta et al., 2019); however, the mechanism of substrate selection is not known. Here, we show helminths synthesize two coq-2 splice forms, coq-2a and coq-2e, and the coq-2e-specific exon is only found in species that synthesize RQ. We show that in Caenorhabditis elegans COQ-2e is required for efficient RQ synthesis and survival in cyanide. Importantly, parasites switch from COQ-2a to COQ-2e as they transit into anaerobic environments. We conclude helminths switch from UQ to RQ synthesis principally via changes in the alternative splicing of coq-2.

EPIC: software toolkit for elution profile-based inference of protein complexes.

Protein complexes are key macromolecular machines of the cell, but their description remains incomplete. We and others previously reported an experimental strategy for global characterization of native protein assemblies based on chromatographic fractionation of biological extracts coupled to precision mass spectrometry analysis (chromatographic fractionation-mass spectrometry, CF-MS), but the resulting data are challenging to process and interpret. Here, we describe EPIC (elution profile-based inference of complexes), a software toolkit for automated scoring of large-scale CF-MS data to define high-confidence multi-component macromolecules from diverse biological specimens. As a case study, we used EPIC to map the global interactome of Caenorhabditis elegans, defining 612 putative worm protein complexes linked to diverse biological processes. These included novel subunits and assemblies unique to nematodes that we validated using orthogonal methods. The open source EPIC software is freely available as a Jupyter notebook packaged in a Docker container (https://hub.docker.com/r/baderlab/bio-epic/).

Rhodoquinone biosynthesis in C. elegans requires precursors generated by the kynurenine pathway.

Parasitic helminths infect over a billion humans. To survive in the low oxygen environment of their hosts, these parasites use unusual anaerobic metabolism - this requires rhodoquinone (RQ), an electron carrier that is made by very few animal species. Crucially RQ is not made or used by any parasitic hosts and RQ synthesis is thus an ideal target for anthelmintics. However, little is known about how RQ is made and no drugs are known to block RQ synthesis. C. elegans makes RQ and can use RQ-dependent metabolic pathways - here, we use C. elegans genetics to show that tryptophan degradation via the kynurenine pathway is required to generate the key amine-containing precursors for RQ synthesis. We show that C. elegans requires RQ for survival in hypoxic conditions and, finally, we establish a high throughput assay for drugs that block RQ-dependent metabolism. This may drive the development of a new class of anthelmintic drugs. This study is a key first step in understanding how RQ is made in parasitic helminths.

The combinatorial control of alternative splicing in C. elegans.

Normal development requires the right splice variants to be made in the right tissues at the right time. The core splicing machinery is engaged in all splicing events, but which precise splice variant is made requires the choice between alternative splice sites-for this to occur, a set of splicing factors (SFs) must recognize and bind to short RNA motifs in the pre-mRNA. In C. elegans, there is known to be extensive variation in splicing patterns across development, but little is known about the targets of each SF or how multiple SFs combine to regulate splicing. Here we combine RNA-seq with in vitro binding assays to study how 4 different C. elegans SFs, ASD-1, FOX-1, MEC-8, and EXC-7, regulate splicing. The 4 SFs chosen all have well-characterised biology and well-studied loss-of-function genetic alleles, and all contain RRM domains. Intriguingly, while the SFs we examined have varied roles in C. elegans development, they show an unexpectedly high overlap in their targets. We also find that binding sites for these SFs occur on the same pre-mRNAs more frequently than expected suggesting extensive combinatorial control of splicing. We confirm that regulation of splicing by multiple SFs is often combinatorial and show that this is functionally significant. We also find that SFs appear to combine to affect splicing in two modes-they either bind in close proximity within the same intron or they appear to bind to separate regions of the intron in a conserved order. Finally, we find that the genes whose splicing are regulated by multiple SFs are highly enriched for genes involved in the cytoskeleton and in ion channels that are key for neurotransmission. Together, this shows that specific classes of genes have complex combinatorial regulation of splicing and that this combinatorial regulation is critical for normal development to occur.

Dietary cholesterol, fats and risk of Parkinson's disease in the Singapore Chinese Health Study.

BACKGROUND: Prospective studies on lipids and risk of Parkinson's disease (PD) in Asian populations are sparse. This study prospectively examined the associations between dietary cholesterol and major fatty acids, and risk of PD among the Chinese in Singapore. METHODS: This study used data from the Singapore Chinese Health Study, a population-based prospective cohort of 63 257 men and women aged 45-74 years in Singapore enrolled in 1993-1998. Dietary intakes of cholesterol and fatty acids were derived from a validated semiquantitative food frequency questionnaire and the Singapore Food Composition Table. Incident PD cases were identified either through follow-up interviews or record linkage analysis with hospital discharge and PD outpatient registries. RESULTS: After an average of 14.6 years, 218 men and 193 women in the cohort developed PD. Dietary cholesterol was associated with statistically significantly lower risk of PD in a dose-dependent manner among men after adjustment for established risk factors for PD and intakes of major fatty acids. Compared to the lowest quartile, HR (95% CI) for the highest quartile was 0.53 (95% CI 0.33 to 0.84) (P for trend=0.006). Among women, dietary monounsaturated fatty acid was inversely associated with PD risk (P for trend=0.033). Compared to the lowest quartile, HR for the highest quartile was 0.44 (95% CI 0.22 to 0.88). There was no statistically significant association between dietary saturated, n-3 and n-6 fatty acids and PD risk. CONCLUSIONS: Higher intakes of cholesterol and monounsaturated fatty acids may reduce risk of PD in men and women, respectively.

Feasibility and safety of intravenous thrombolysis in multiethnic Asian stroke patients in Singapore.

Treatment rates with intravenously administered tissue plasminogen activator (IV-tPA) in acute ischemic stroke (IS) remain low in Asian populations. Various logistic obstacles and higher anticipated bleeding risk in Asians are major concerns. We report on the feasibility and safety of IV-tPA therapy at our tertiary care center. Consecutive acute IS patients eligible for thrombolysis were treated with low-dose (maximum 50 mg) IV-tPA between January 2000 and September 2006 and with standard-dose (maximum 90 mg) IV-tPA between October 2006 and May 2008. The efficacy of IV-tPA was assessed by the modified Rankin Scale (mRS) score at 3 months and by absolute changes in the National Institute of Health Stroke Scale (NIHSS) score at hospital discharge and 3 months. The safety of IV-tPA was assessed by the rate of symptomatic intracranial hemorrhage (SICH). A total of 130 patients were included (mean age, 60±13 years; 60% males; median NIHSS score, 14). A total of 48 patients received low-dose IV-tPA, and 82 patients received standard-dose IV-tPA. The median onset to treatment time was 160 minutes. Some 59% of the patients achieved functional independence (mRS score 0-1) at 3 months with standard-dose tPA, compared with 35% in the low-dose group (P=.011). SICH occurred more frequently with the low dose (14.5%) than with the standard dose (1.2%; P=.004). In a multivariate logistic regression model, lower admission NIHSS score (odds ratio [OR]=0.78 per 1-point increase; 95% confidence interval [CI]=0.70-0.88), lower pretreatment blood glucose level (OR=0.76 per 1 mmol/L increase; 95% CI=0.60-0.95), shorter time from symptom onset to IV-tPA bolus (OR=0.97 per 1-minute increase; 95% CI=0.94-1.0), and standard-dose IV-tPA (OR=12.49; 95% CI=2.9-53.89) were associated with a higher likelihood for functional independence at 3 months. Our data indicate that standard-dose IV-tPA (0.9 mg/kg) was feasible and safe for treating acute IS in our multiethnic Asian population in Singapore.

Differential effects of black versus green tea on risk of Parkinson's disease in the Singapore Chinese Health Study.

Data from Asian populations on dietary and lifestyle factors associated with Parkinson's disease are sparse. In 1993-2005, the authors examined these factors in relation to Parkinson's disease in the Singapore Chinese Health Study, a prospective cohort of 63,257 Chinese men and women. Baseline data were collected through in-person interviews using structured questionnaires. All 157 incident Parkinson's disease cases were identified either through follow-up interviews or via linkage with hospital discharge databases and Parkinson's disease outpatient registries and were confirmed by review of medical records. Current versus never smokers exhibited a reduced risk of Parkinson's disease (relative risk = 0.29, 95% confidence interval: 0.16, 0.52). Total caffeine intake was inversely related to Parkinson's disease risk (p for trend = 0.002); the relative risk for the highest versus lowest quartile was 0.55 (95% confidence interval: 0.35, 0.88). Black tea, a caffeine-containing beverage, showed an inverse association with Parkinson's disease risk that was not confounded by total caffeine intake or tobacco smoking (p for trend = 0.0006; adjusted relative risk for the highest vs. lowest tertile of intake = 0.29, 95% confidence interval: 0.13, 0.67). Green tea drinking was unrelated to Parkinson's disease risk. Diet had no strong influence on risk. Ingredients of black tea other than caffeine appear to be responsible for the beverage's inverse association with Parkinson's disease.

Post-hypoxic early selective putaminal necrosis followed by delayed extensive sub-cortical demyelination.

OBJECTIVE: To describe the patterns of early and delayed hypoxic damage to the brain parenchyma. METHODS: This paper reports a case with interesting clinical course and MRI brain changes in a patient following a single hypoxic-anoxic exposure after an alcoholic binge. RESULTS: Bilaterally symmetrical putaminal necrosis was noted in the initial MRI, but subsequent follow-up revealed extensive demyelination of the sub-cortical white matter, associated with the clinical deterioration. CONCLUSIONS: The brain, in general, and the neurons in caudate nucleus, putamen, globus pallidus and cerebral white matter, in particular, are susceptible to hypoxic injury. These changes may occur simultaneously and early or sequentially and late.