Tau/DDX6 interaction increases microRNA activity

Tauopathies, such as Alzheimer's disease, are characterized by intracellular aggregates of insoluble Tau proteins. Originally described as a microtubule binding protein, recent studies demonstrated additional physiological roles for Tau. The fact that a single protein can regulate multiple cellular functions has posed challenge in terms of understanding mechanistic cues behind the pathology. Here, we used tandem-affinity purification methodology coupled to mass spectrometry to identify novel interaction partners. We found that Tau interacts with DDX6, a DEAD box RNA helicase involved in translation repression and mRNA decay as well as in the miRNA pathway. Our results demonstrate that Tau increases the silencing activity of the miRNA let-7a, miR-21 and miR-124 through DDX6. Importantly, Tau mutations (P301S, P301L) found in the inherited tauopathies, frontotemporal dementia and parkinsonism linked to chromosome 17, disrupt Tau/DDX6 interaction and impair gene silencing by let-7a. Altogether, these data demonstrated a new unexpected role for Tau in regulating miRNA activity.     

Distribution,food preference,and trophic position of the corallivorous fireworm Hermodice carunculata in a Caribbean coral reef

The fireworm Hermodice carunculata is a facultative corallivore on coral reefs. It can interact with algal overgrowth to cause coral mortality. However, because of its cryptic nature, little is known about its ecology. We used micropredator attracting devices (MADs) and stable isotope analyses to provide insights into the distribution and diet of H. carunculata in a coral reef on Curaçao, southern Caribbean. MADs consisted of algal clumps inside accessible mesh nets which H. carunculata could use as refuge. To obtain indications on its distribution pattern, MADs filled with Halimeda opuntia were deployed in different reef habitats ranging from 0 to 16 m water depth. Fireworms were found inside MADs in all reef habitats, indicating that they have a widespread horizontal and vertical distribution, ranging from the shoreline to the deeper reef slope. On the reef crest, MADs were filled using different algal species and deployed on dead or live scleractinian corals. MADs hosted more fireworms when placed on live corals, regardless of algal species used, suggesting that algal-induced corallivory may be widespread. To test for food preferences, different food sources were added inside the MADs. Fireworms detected potential prey within 6 h and were significantly more attracted by decaying corals and raw fish than by live corals, hydrozoans, or gorgonians. Stable isotope analyses indicated detritus, macroalgae, and scleractinian corals as potential food sources and revealed an ontogenetic dietary shift toward enriched δ ¹³C and δ ¹⁵N values with increasing fireworm size, suggesting that large-sized individuals feed on food sources of higher trophic levels. Our findings highlight H. carunculata as a widespread, and omnivorous scavenger that has the potential to switch feeding toward weakened or stressed corals, thereby likely acting as a harmful corallivore on degraded reefs.     

Organic Matter Degradation Drives Benthic Cyanobacterial Mat Abundance on Caribbean Coral Reefs

Benthic cyanobacterial mats (BCMs) are impacting coral reefs worldwide. However, the factors and mechanisms driving their proliferation are unclear. We conducted a multi-year survey around the Caribbean island of Curaçao, which revealed highest BCM abundance on sheltered reefs close to urbanised areas. Reefs with high BCM abundance were also characterised by high benthic cover of macroalgae and low cover of corals. Nutrient concentrations in the water-column were consistently low, but markedly increased just above substrata (both sandy and hard) covered with BCMs. This was true for sites with both high and low BCM coverage, suggesting that BCM growth is stimulated by a localised, substrate-linked release of nutrients from the microbial degradation of organic matter. This hypothesis was supported by a higher organic content in sediments on reefs with high BCM coverage, and by an in situ experiment which showed that BCMs grew within days on sediments enriched with organic matter (Spirulina). We propose that nutrient runoff from urbanised areas stimulates phototrophic blooms and enhances organic matter concentrations on the reef. This organic matter is transported by currents and settles on the seabed at sites with low hydrodynamics. Subsequently, nutrients released from the organic matter degradation fuel the growth of BCMs. Improved management of nutrients generated on land should lower organic loading of sediments and other benthos (e.g. turf and macroalgae) to reduce BCM proliferation on coral reefs.     

Effects of Asparagopsis taxiformis metabolites on the feeding behaviour of post-larval Acanthurus triostegus

Our study highlights the effect of the macroalgae Asparagopsis taxiformis on the feeding behaviour of the tropical surgeonfish Acanthurus triostegus. The presence of A. taxiformis chemical cues reduced A. triostegus feeding, suggesting that the presence of this algae could affect not only the survival of fish in the post-larval stage, but also alter the grazing pressure on coral reefs.     

In situ oxygen dynamics in coral-algal interactions

Background

Coral reefs degrade globally at an alarming rate, with benthic algae often replacing corals. However, the extent to which benthic algae contribute to coral mortality, and the potential mechanisms involved, remain disputed. Recent laboratory studies suggested that algae kill corals by inducing hypoxia on the coral surface, through stimulated microbial respiration.

Methods/Findings

We examined the main premise of this hypothesis by measuring in situ oxygen microenvironments at the contact interface between the massive coral Porites spp. and turf algae, and between Porites spp. and crustose coralline algae (CCA). Oxygen levels at the interface were similar to healthy coral tissue and ranged between 300–400 µM during the day. At night, the interface was hypoxic (∼70 µM) in coral-turf interactions and close to anoxic (∼2 µM) in coral-CCA interactions, but these values were not significantly different from healthy tissue. The diffusive boundary layer (DBL) was about three times thicker at the interface than above healthy tissue, due to a depression in the local topography. A numerical model, developed to analyze the oxygen profiles above the irregular interface, revealed strongly reduced net photosynthesis and dark respiration rates at the coral-algal interface compared to unaffected tissue during the day and at night, respectively.

Conclusions/Significance

Our results showed that hypoxia was not a consistent feature in the microenvironment of the coral-algal interface under in situ conditions. Therefore, hypoxia alone is unlikely to be the cause of coral mortality. Due to the modified topography, the interaction zone is distinguished by a thicker diffusive boundary layer, which limits the local metabolic activity and likely promotes accumulation of potentially harmful metabolic products (e.g., allelochemicals and protons). Our study highlights the importance of mass transfer phenomena and the need for direct in situ measurements of microenvironmental conditions in studies on coral stress.     

Head lice in the Netherlands: Susceptibility for insecticides in field samples

A double application of 1% lindane failed to cure head louse infestations in 38 out of 110 children in two cities. Residue tests showed considerable resistance levels in all samples from fourteen cities. The average LD 50's were 0.9% lindane and 2% dieldrin. A baseline for malathion was determined. LD 50 is 0.1% malathion. The results show that field-collected head lice can be used for insecticidal testing.

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Zusammenfassung In neun Schulen und zwei Städten wurden Kinder mit aktiven Kopfläusen zweimal in wöchentlichem Abstand mit einer alkoholischen einprozentigen Lindanlösung behandelt. In 38 von 110 Fällen versagte diese Behandlung, was auf Lindanresistenz in diesen Orten hindeutet. In vitro-Versuche wurden mit Läusen aus vierzehn Städten durchgeführt und ergaben durchwegs einen ähnlichen Resistenzgrad wie in den Feldversuchen.Beim Vergleich der gewogenen Durchschnitte war kein Einfluss einer erhöhten Mortalität (über 20%) in den unbehandelten Kontrollen auf die Versuchsresultate festzustellen. LD-50-Werte von 0.9% für Lindan und 2% für Dieldrin weisen auf die in den Niederlanden verbreitete Lindanresistenz hin. Die Grundlinie der Wirkung von Malathion, als Ersatz für Lindan, wurde bestimmt und eine LD 50 von weniger als 0,1% ermittelt. Einige Tiere überlebten bei 0,4% und bei 0,8% und zwar im Gegensatz zu anderweitigen Beobachtungen. Zur Unterscheidung resistenter und empfindlicher Läuse sollten deshalb die Testkonzentrationen erhöht werden.Die Resultate zeigen, dass im Feld gesammelte Kopfläuse für Insektizidteste geeignet sind. Beim Test sollte die Beobachtungszeit von 24 auf 18 Stunden verkürzt werden, wodurch eine annehmbarere Mortalität in Unbehandelt bei halbierter Wirkung erreicht wird.

     

Enhanced passive surveillance dengue infection among febrile children: Prevalence,co-infections and associated factors in Cameroon

Dengue virus (DENV) causes a spectrum of diseases ranging from asymptomatic, mild febrile to a life-threatening illness: dengue hemorrhagic fever. The main clinical symptom of dengue is fever, similar to that of malaria. The prevalence of dengue virus infection, alone or in association with other endemic infectious diseases in children in Cameroon is unknown. The aim of this study was to determine the prevalence of dengue, malaria and HIV in children presenting with fever and associated risk factors.Dengue overall prevalence was 20.2%, Malaria cases were 52.7% and HIV cases represented 12.6%. The prevalence of dengue-HIV co-infection was 6.0% and that of Malaria-dengue co-infection was 19.5%. Triple infection prevalence was 4.3%. Dengue virus infection is present in children and HIV-Dengue or Dengue- Malaria co-infections are common. Dengue peak prevalence was between August and October. Sex and age were not associated with dengue and dengue co-infections. However, malaria as well as HIV were significantly associated with dengue (P = 0.001 and 0.028 respectively). The diagnosis of dengue and Malaria should be carried out routinely for better management of fever.