Whiskers as hydrodynamic prey sensors in foraging seals.

The darkness of the deep ocean limits the vision of diving predators, except when prey emit bioluminescence. It is hypothesized that deep-diving seals rely on highly developed whiskers to locate their prey. However, if and how seals use their whiskers while foraging in natural conditions remains unknown. We used animal-borne tags to show that free-ranging elephant seals use their whiskers for hydrodynamic prey sensing. Small, cheek-mounted video loggers documented seals actively protracting their whiskers in front of their mouths with rhythmic whisker movement, like terrestrial mammals exploring their environment. Seals focused their sensing effort at deep foraging depths, performing prolonged whisker protraction to detect, pursue, and capture prey. Feeding-event recorders with light sensors demonstrated that bioluminescence contributed to only about 20% of overall foraging success, confirming that whiskers play the primary role in sensing prey. Accordingly, visual prey detection complemented and enhanced prey capture. The whiskers' role highlights an evolutionary alternative to echolocation for adapting to the extreme dark of the deep ocean environment, revealing how sensory abilities shape foraging niche segregation in deep-diving mammals. Mammals typically have mobile facial whiskers, and our study reveals the significant function of whiskers in the natural foraging behavior of a marine predator. We demonstrate the importance of field-based sensory studies incorporating multimodality to better understand how multiple sensory systems are complementary in shaping the foraging success of predators.

Circumpolar assessment of mercury contamination: the Adélie penguin as a bioindicator of Antarctic marine ecosystems.

Due to its persistence and potential ecological and health impacts, mercury (Hg) is a global pollutant of major concern that may reach high concentrations even in remote polar oceans. In contrast to the Arctic Ocean, studies documenting Hg contamination in the Southern Ocean are spatially restricted and large-scale monitoring is needed. Here, we present the first circumpolar assessment of Hg contamination in Antarctic marine ecosystems. Specifically, the Adélie penguin (Pygoscelis adeliae) was used as a bioindicator species, to examine regional variation across 24 colonies distributed across the entire Antarctic continent. Mercury was measured on body feathers collected from both adults (n = 485) and chicks (n = 48) between 2005 and 2021. Because penguins' diet represents the dominant source of Hg, feather δ13C and δ15N values were measured as proxies of feeding habitat and trophic position. As expected, chicks had lower Hg concentrations (mean ± SD: 0.22 ± 0.08 µg·g‒1) than adults (0.49 ± 0.23 µg·g‒1), likely because of their shorter bioaccumulation period. In adults, spatial variation in feather Hg concentrations was driven by both trophic ecology and colony location. The highest Hg concentrations were observed in the Ross Sea, possibly because of a higher consumption of fish in the diet compared to other sites (krill-dominated diet). Such large-scale assessments are critical to assess the effectiveness of the Minamata Convention on Mercury. Owing to their circumpolar distribution and their ecological role in Antarctic marine ecosystems, Adélie penguins could be valuable bioindicators for tracking spatial and temporal trends of Hg across Antarctic waters in the future.

Postnatal liver functional maturation requires Cnot complex-mediated decay of mRNAs encoding cell cycle and immature liver genes.

Liver development involves dramatic gene expression changes mediated by transcriptional and post-transcriptional control. Here, we show that the Cnot deadenylase complex plays a crucial role in liver functional maturation. The Cnot3 gene encodes an essential subunit of the Cnot complex. Mice lacking Cnot3 in liver have reduced body and liver masses, and they display anemia and severe liver damage. Histological analyses indicate that Cnot3-deficient (Cnot3-/- ) hepatocytes are irregular in size and morphology, resulting in formation of abnormal sinusoids. We observe hepatocyte death, increased abundance of mitotic and mononucleate hepatocytes, and inflammation. Cnot3-/- livers show increased expression of immune response-related, cell cycle-regulating and immature liver genes, while many genes relevant to liver functions, such as oxidation-reduction, lipid metabolism and mitochondrial function, decrease, indicating impaired liver functional maturation. Highly expressed mRNAs possess elongated poly(A) tails and are stabilized in Cnot3-/- livers, concomitant with an increase of the proteins they encode. In contrast, transcription of liver function-related mRNAs was lower in Cnot3-/- livers. We detect efficient suppression of Cnot3 protein postnatally, demonstrating the crucial contribution of mRNA decay to postnatal liver functional maturation.

CNOT1 regulates circadian behaviour through Per2 mRNA decay in a deadenylation-dependent manner.

Circadian clocks are an endogenous internal timekeeping mechanism that drives the rhythmic expression of genes, controlling the 24 h oscillatory pattern in behaviour and physiology. It has been recently shown that post-transcriptional mechanisms are essential for controlling rhythmic gene expression. Controlling the stability of mRNA through poly(A) tail length modulation is one such mechanism. In this study, we show that Cnot1, encoding the scaffold protein of the CCR4-NOT deadenylase complex, is highly expressed in the suprachiasmatic nucleus, the master timekeeper. CNOT1 deficiency in mice results in circadian period lengthening and alterations in the mRNA and protein expression patterns of various clock genes, mainly Per2. Per2 mRNA exhibited a longer poly(A) tail and increased mRNA stability in Cnot1+/- mice. CNOT1 is recruited to Per2 mRNA through BRF1 (ZFP36L1), which itself oscillates in antiphase with Per2 mRNA. Upon Brf1 knockdown, Per2 mRNA is stabilized leading to increased PER2 expression levels. This suggests that CNOT1 plays a role in tuning and regulating the mammalian circadian clock.

Hepatic posttranscriptional network comprised of CCR4-NOT deadenylase and FGF21 maintains systemic metabolic homeostasis.

Whole-body metabolic homeostasis is tightly controlled by hormone-like factors with systemic or paracrine effects that are derived from nonendocrine organs, including adipose tissue (adipokines) and liver (hepatokines). Fibroblast growth factor 21 (FGF21) is a hormone-like protein, which is emerging as a major regulator of whole-body metabolism and has therapeutic potential for treating metabolic syndrome. However, the mechanisms that control FGF21 levels are not fully understood. Herein, we demonstrate that FGF21 production in the liver is regulated via a posttranscriptional network consisting of the CCR4-NOT deadenylase complex and RNA-binding protein tristetraprolin (TTP). In response to nutrient uptake, CCR4-NOT cooperates with TTP to degrade AU-rich mRNAs that encode pivotal metabolic regulators, including FGF21. Disruption of CCR4-NOT activity in the liver, by deletion of the catalytic subunit CNOT6L, increases serum FGF21 levels, which ameliorates diet-induced metabolic disorders and enhances energy expenditure without disrupting bone homeostasis. Taken together, our study describes a hepatic CCR4-NOT/FGF21 axis as a hitherto unrecognized systemic regulator of metabolism and suggests that hepatic CCR4-NOT may serve as a target for devising therapeutic strategies in metabolic syndrome and related morbidities.

The mitochondrial protein PGAM5 suppresses energy consumption in brown adipocytes by repressing expression of uncoupling protein 1.

Accumulating evidence suggests that brown adipose tissue (BAT) is a potential therapeutic target for managing obesity and related diseases. PGAM family member 5, mitochondrial serine/threonine protein phosphatase (PGAM5), is a protein phosphatase that resides in the mitochondria and regulates many biological processes, including cell death, mitophagy, and immune responses. Because BAT is a mitochondria-rich tissue, we have hypothesized that PGAM5 has a physiological function in BAT. We previously reported that PGAM5-knockout (KO) mice are resistant to severe metabolic stress. Importantly, lipid accumulation is suppressed in PGAM5-KO BAT, even under unstressed conditions, raising the possibility that PGAM5 deficiency stimulates lipid consumption. However, the mechanism underlying this observation is undetermined. Here, using an array of biochemical approaches, including quantitative RT-PCR, immunoblotting, and oxygen consumption assays, we show that PGAM5 negatively regulates energy expenditure in brown adipocytes. We found that PGAM5-KO brown adipocytes have an enhanced oxygen consumption rate and increased expression of uncoupling protein 1 (UCP1), a protein that increases energy consumption in the mitochondria. Mechanistically, we found that PGAM5 phosphatase activity and intramembrane cleavage are required for suppression of UCP1 activity. Furthermore, utilizing a genome-wide siRNA screen in HeLa cells to search for regulators of PGAM5 cleavage, we identified a set of candidate genes, including phosphatidylserine decarboxylase (PISD), which catalyzes the formation of phosphatidylethanolamine at the mitochondrial membrane. Taken together, these results indicate that PGAM5 suppresses mitochondrial energy expenditure by down-regulating UCP1 expression in brown adipocytes and that its phosphatase activity and intramembrane cleavage are required for UCP1 suppression.

Seasonal resource pulses and the foraging depth of a Southern Ocean top predator.

Seasonal resource pulses can have enormous impacts on species interactions. In marine ecosystems, air-breathing predators often drive their prey to deeper waters. However, it is unclear how ephemeral resource pulses such as near-surface phytoplankton blooms alter the vertical trade-off between predation avoidance and resource availability in consumers, and how these changes cascade to the diving behaviour of top predators. We integrated data on Weddell seal diving behaviour, diet stable isotopes, feeding success and mass gain to examine shifts in vertical foraging throughout ice break-out and the resulting phytoplankton bloom each year. We also tested hypotheses about the likely location of phytoplankton bloom origination (advected or produced in situ where seals foraged) based on sea ice break-out phenology and advection rates from several locations within 150 km of the seal colony. In early summer, seals foraged at deeper depths resulting in lower feeding rates and mass gain. As sea ice extent decreased throughout the summer, seals foraged at shallower depths and benefited from more efficient energy intake. Changes in diving depth were not due to seasonal shifts in seal diets or horizontal space use and instead may reflect a change in the vertical distribution of prey. Correspondence between the timing of seal shallowing and the resource pulse was variable from year to year and could not be readily explained by our existing understanding of the ocean and ice dynamics. Phytoplankton advection occurred faster than ice break-out, and seal dive shallowing occurred substantially earlier than local break-out. While there remains much to be learned about the marine ecosystem, it appears that an increase in prey abundance and accessibility via shallower distributions during the resource pulse could synchronize life-history phenology across trophic levels in this high-latitude ecosystem.

The clinical usage of liposomal amphotericin B in patients receiving renal replacement therapy in Japan: a nationwide observational study.

BACKGROUND: Liposomal amphotericin B (L-AMB), a broad-spectrum antifungicidal drug, is often used to treat fungal infections. However, clinical evidence of its use in patients with renal dysfunction, especially those receiving renal replacement therapy (RRT), is limited. Therefore, we evaluated the usage and occurrence of adverse reactions during L-AMB therapy in patients undergoing RRT. METHODS: Using claims data and laboratory data, we retrospectively evaluated patients who were administered L-AMB. The presence of comorbidities, mortality rate, treatment with L-AMB and other anti-infective agents, and the incidence of adverse reactions were compared between patients receiving RRT, including continuous renal replacement therapy (CRRT) and maintenance hemodialysis (HD), and those that did not receive RRT. RESULTS: In total, 900 cases met the eligibility criteria: 24, 19, and 842 cases in the maintenance HD, CRRT, and non-RRT groups, respectively. Of the patients administered L-AMB, mortality at discharge was higher for those undergoing either CRRT (15/19; 79%) or maintenance HD (16/24; 67%) than for those not receiving RRT (353/842; 42%). After propensity score matching, the average daily and cumulative dose, treatment duration, and dosing interval for L-AMB were not significantly different between patients receiving and not receiving RRT. L-AMB was used as the first-line antifungal agent for patients undergoing CRRT in most cases (12/19; 63%). Although the number of subjects was limited, the incidence of adverse events did not markedly differ among the groups. CONCLUSION: L-AMB may be used for patients undergoing maintenance HD or CRRT without any dosing, duration, or interval adjustments.

Efficacy of early administration of liposomal amphotericin B in patients with septic shock: A nationwide observational study.

INTRODUCTION: Liposomal amphotericin B (L-AMB), a broad spectrum anti-fungicidal drug, is often administered to treat invasive fungal infections (IFIs). However, the most suitable time to initiate treatment in septic shock patients with IFI is unknown. METHODS: Patients with septic shock treated with L-AMB were identified from the Japanese Diagnosis Procedure Combination national database and were stratified according to L-AMB treatment initiation either at septic shock onset (early L-AMB group) or after the onset (delayed L-AMB group) to determine their survival rates following septic shock onset and the shock cessation period. RESULTS: We identified 141 patients administered L-AMB on the day of or after septic shock onset: 60 patients received early treatment, whereas 81 patients received delayed treatment. Survival rates after septic shock onset were higher in the early L-AMB group than in the delayed L-AMB group (4 weeks: 68.4% vs 57.9%, P = 0.197; 6 weeks: 62.2% vs 44.5%, P = 0.061; 12 weeks: 43.4% vs 35.0%, P = 0.168, respectively). The septic shock cessation period was shorter in the early L-AMB group than in the delayed L-AMB group (7.0 ± 7.0 days vs 16.5 ± 15.4 days, P < 0.001), with a significant difference confirmed after adjusting for confounding factors with propensity score matching (7.1 ± 7.2 days vs 16.7 ± 14.0 days, P = 0.001). CONCLUSION: Early L-AMB administration at septic shock onset may be associated with early shock cessation.

Association between potassium supplementation and the occurrence of acute kidney injury in patients with hypokalemia administered liposomal amphotericin B: a nationwide observational study.

BACKGROUND: Hypokalemia and acute kidney injury (AKI) occur in patients administered liposomal amphotericin B (L-AMB), a wide-spectrum anti-fungicidal drug. However, the association between potassium supplementation and the occurrence of AKI in patients with hypokalemia who were administered L-AMB is not well understood. METHODS: Using nationwide claims data and laboratory data, the occurrence of AKI during L-AMB treatment was retrospectively compared between patients with hypokalemia who were or were not supplemented with potassium and between those adequately or inadequately supplemented with potassium (serum potassium levels corrected to ≥3.5 mEq/L or remained < 3.5 mEq/L, respectively) before or after L-AMB treatment initiation. RESULTS: We identified 118 patients who developed hypokalemia before L-AMB treatment initiation (43 received potassium supplementation [25 adequate and 18 inadequate supplementation] and 75 did not receive potassium supplementation), and 117 patients who developed hypokalemia after L-AMB initiation (79 received potassium supplementation [including 23 adequate and 15 inadequate supplementation] and 38 did not receive potassium supplementation). The occurrence of any stage of AKI was similar between patients with hypokalemia, regardless of potassium supplementation (i.e., before L-AMB treatment initiation [supplementation, 51%; non-supplementation, 45%; P = 0.570] or after L-AMB initiation [supplementation, 28%; non-supplementation, 32%; P = 0.671]). After adjusting for confounding factors, we found that the occurrence of any stage of AKI was not associated with potassium supplementation before L-AMB initiation (odds ratio [OR]: 1.291, 95% confidence interval [CI]: 0.584-2.852, P = 0.528) or after L-AMB initiation (OR: 0.954, 95% CI: 0.400-2.275, P = 0.915). The occurrence of any stage of AKI tended to decline in patients with hypokalemia who were adequately supplemented with potassium (44%) before, but not after, L-AMB initiation relative to that in patients inadequately supplemented with potassium (61%), however this result was not significant (P = 0.358). CONCLUSION: Potassium supplementation was not associated with any stage of AKI in patients with hypokalemia who were administered L-AMB.

Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals.

Knowledge of the diet of marine mammals is fundamental to understanding their role in marine ecosystems and response to environmental change. Recently, animal-borne video cameras have revealed the diet of marine mammals that make short foraging trips. However, novel approaches that allocate video time to target prey capture events is required to obtain diet information for species that make long foraging trips over great distances. We combined satellite telemetry and depth recorders with newly developed date-/time-, depth- and acceleration-triggered animal-borne video cameras to examine the diet of female northern elephant seals during their foraging migrations across the eastern North Pacific. We obtained 48.2 h of underwater video, from cameras mounted on the head (n=12) and jaw (n=3) of seals. Fish dominated the diet (78% of 697 prey items recorded) across all foraging locations (range: 37-55°N, 122-152°W), diving depths (range: 238-1167 m) and water temperatures (range: 3.2-7.4°C), while squid comprised only 7% of the diet. Identified prey included fish such as myctophids, Merluccius sp. and Icosteus aenigmaticus, and squid such as Histioteuthis sp., Octopoteuthis sp. and Taningia danae Our results corroborate fatty acid analysis, which also found that fish are more important in the diet, and are in contrast to stomach content analyses that found cephalopods to be the most important component of the diet. Our work shows that in situ video observation is a useful method for studying the at-sea diet of long-ranging marine predators.

Essential functions of the CNOT7/8 catalytic subunits of the CCR4-NOT complex in mRNA regulation and cell viability.

Shortening of mRNA poly(A) tails (deadenylation) to trigger their decay is mediated mainly by the CCR4-NOT deadenylase complex. While four catalytic subunits (CNOT6, 6L 7, and 8) have been identified in the mammalian CCR4-NOT complex, their individual biological roles are not fully understood. In this study, we addressed the contribution of CNOT7/8 to viability of primary mouse embryonic fibroblasts (MEFs). We found that MEFs lacking CNOT7/8 expression [Cnot7/8-double knockout (dKO) MEFs] undergo cell death, whereas MEFs lacking CNOT6/6L expression (Cnot6/6l-dKO MEFs) remain viable. Co-immunoprecipitation analyses showed that CNOT6/6L are also absent from the CCR4-NOT complex in Cnot7/8-dKO MEFs. In contrast, either CNOT7 or CNOT8 still interacts with other subunits in the CCR4-NOT complex in Cnot6/6l-dKO MEFs. Exogenous expression of a CNOT7 mutant lacking catalytic activity in Cnot7/8-dKO MEFs cannot recover cell viability, even though CNOT6/6L exists to some extent in the CCR4-NOT complex, confirming that CNOT7/8 is essential for viability. Bulk poly(A) tail analysis revealed that mRNAs with longer poly(A) tails are more numerous in Cnot7/8-dKO MEFs than in Cnot6/6l-dKO MEFs. Consistent with elongated poly(A) tails, more mRNAs are upregulated and stabilized in Cnot7/8-dKO MEFs than in Cnot6/6l-dKO MEFs. Importantly, Cnot6/6l-dKO mice are viable and grow normally to adulthood. Taken together, the CNOT7/8 catalytic subunits are essential for deadenylation, which is necessary to maintain cell viability, whereas CNOT6/6L are not.

Investigation of the 2018 thick-billed murre (Uria lomvia) die-off on St. Lawrence Island rules out food shortage as the cause.

Die-offs of seabirds in Alaska have occurred with increased frequency since 2015. In 2018, on St. Lawrence Island, seabirds were reported washing up dead on beaches starting in late May, peaking in June, and continuing until early August. The cause of death was documented to be starvation, leading to the conclusion that a severe food shortage was to blame. We use physiology and colony-based observations to examine whether food shortage is a sufficient explanation for the die-off, or if evidence indicates an alternative cause of starvation such as disease. Specifically, we address what species were most affected, the timing of possible food shortages, and food shortage severity in a historical context. We found that thick-billed murres (Uria lomvia) were most affected by the die-off, making up 61% of all bird carcasses encountered during beach surveys. Thick-billed murre carcasses were proportionately more numerous (26:1) than would be expected based on ratios of thick-billed murres to co-occurring common murres (U. aalge) observed on breeding study plots (7:1). Concentrations of the stress hormone corticosterone, a reliable physiological indicator of nutritional stress, in thick-billed murre feathers grown in the fall indicate that foraging conditions in the northern Bering Sea were poor in the fall of 2017 and comparable in severity to those experienced by murres during the 1976-1977 Bering Sea regime shift. Concentrations of corticosterone in feathers grown during the pre-breeding molt indicate that foraging conditions in late winter 2018 were similar to previous years. The 2018 murre egg harvest in the village of Savoonga (on St. Lawrence Is.) was one-fifth the 1993-2012 average, and residents observed that fewer birds laid eggs in 2018. Exposure of thick-billed murres to nutritional stress in August, however, was no different in 2018 compared to 2016, 2017, and 2019, and was comparable to levels observed on St. George Island in 2003-2017. Prey abundance, measured by the National Oceanic and Atmospheric Administration in bottom-trawl surveys, was also similar in 2018 to 2017 and 2019, supporting the evidence that food was not scarce in the summer of 2018 in the vicinity of St. Lawrence Island. Of two moribund thick-billed murres collected at the end of the mortality event, one tested positive for a novel re-assortment H10 strain of avian influenza with Eurasian components, likely contracted during the non-breeding season. It is not currently known how widely spread infection of murres with the novel virus was, thus insufficient evidence exists to attribute the die-off to an outbreak of avian influenza. We conclude that food shortage alone is not an adequate explanation for the mortality of thick-billed murres in 2018, and highlight the importance of rapid response to mortality events in order to document alternative or confounding causes of mortality.

Niche partitioning of sympatric penguins by leapfrog foraging appears to be resilient to climate change.

Interspecific competition can drive niche partitioning along multidimensional axes, including allochrony. Competitor matching will arise where the phenology of sympatric species with similar ecological requirements responds to climate change at different rates such that allochrony is reduced. Our study quantifies the degree of niche segregation in foraging areas and depths that arises from allochrony in sympatric Adélie and chinstrap penguins and explores its resilience to climate change. Three-dimensional tracking data were sampled during all stages of the breeding season and were used to parameterise a behaviour-based model that quantified spatial overlap of foraging areas under different scenarios of allochrony. The foraging ranges of the two species were similar within breeding stages, but differences in their foraging ranges between stages, combined with the observed allochrony of 28 days, resulted in them leapfrogging each other through the breeding season such that they were exploiting different foraging locations on the same calendar dates. Allochrony reduced spatial overlap in the peripheral utilisation distribution of the two species by 54.0% over the entire breeding season, compared to a scenario where the two species bred synchronously. Analysis of long-term phenology data revealed that both species advanced their laying dates in relation to October air temperatures at the same rate, preserving allochrony and niche partitioning. However, if allochrony is reduced by just a single day, the spatial overlap of the core utilisation distribution increased by an average of 2.1% over the entire breeding season. Niche partitioning between the two species by allochrony appears to be resilient to climate change and so competitor matching cannot be implicated in the observed population declines of the two penguin species across the Western Antarctic Peninsula.

Wintering in the Western Subarctic Pacific Increases Mercury Contamination of Red-Legged Kittiwakes.

Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in different habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used kittiwakes as bioindicators of MeHg concentrations in remote mesopelagic systems by examining how wintering distribution and habitat affected kittiwakes' mercury exposure. In 2011-2017, we sampled winter-grown feathers on St. George Island, Alaska, from birds equipped with geolocation loggers. We measured total mercury (THg) and nitrogen stable isotopes in nape and head feathers grown during winter, respectively. THg concentration of kittiwake nape feathers averaged 4.61 ± 0.97 µg/g dry weight. Hierarchical cluster analysis was used to classify winter habitats with remotely sensed environmental variables along each bird's track. Five habitat clusters were identified. Birds that spent more time in the Western Subarctic Gyre and those that wintered further south had elevated THg concentrations. In contrast to THg, trophic level varied annually but did not show strong spatial patterns. Our results documented spatial variability in THg exposure based on the oceanic wintering locations of red-legged kittiwakes and highlight their use as a bioindicator of MeHg across ocean basins.

The CCR4-NOT Deadenylase Complex Maintains Adipocyte Identity.

Shortening of poly(A) tails triggers mRNA degradation; hence, mRNA deadenylation regulates many biological events. In the present study, we generated mice lacking the Cnot1 gene, which encodes an essential scaffold subunit of the CCR4-NOT deadenylase complex in adipose tissues (Cnot1-AKO mice) and we examined the role of CCR4-NOT in adipocyte function. Cnot1-AKO mice showed reduced masses of white adipose tissue (WAT) and brown adipose tissue (BAT), indicating abnormal organization and function of those tissues. Indeed, Cnot1-AKO mice showed hyperinsulinemia, hyperglycemia, insulin resistance, and glucose intolerance and they could not maintain a normal body temperature during cold exposure. Muscle-like fibrous material appeared in both WAT and BAT of Cnot1-AKO mice, suggesting the acquisition of non-adipose tissue characteristics. Gene expression analysis using RNA-sequencing (RNA-seq) showed that the levels of adipose tissue-related mRNAs, including those of metabolic genes, decreased, whereas the levels of inflammatory response-related mRNAs increased. These data suggest that the CCR4-NOT complex ensures proper adipose tissue function by maintaining adipocyte-specific mRNAs at appropriate levels and by simultaneously suppressing mRNAs that would impair adipocyte function if overexpressed.

Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins (Pygoscelis adeliae).

The Southern Ocean is currently experiencing major environmental changes, including in sea-ice cover. Such changes strongly influence ecosystem structure and functioning and affect the survival and reproduction of predators such as seabirds. These effects are likely mediated by reduced availability of food resources. As such, seabirds are reliable eco-indicators of environmental conditions in the Antarctic region. Here, based on 9 years of sea-ice data, we found that the breeding success of Adélie penguins (Pygoscelis adeliae) reaches a peak at intermediate sea-ice cover (ca. 20%). We further examined the effects of sea-ice conditions on the foraging activity of penguins, measured at multiple scales from individual dives to foraging trips. Analysis of temporal organisation of dives, including fractal and bout analyses, revealed an increasingly consistent behaviour during years with extensive sea-ice cover. The relationship between several dive parameters and sea-ice cover in the foraging area appears to be quadratic. In years of low and high sea-ice cover, individuals adjusted their diving effort by generally diving deeper, more frequently and by resting at the surface between dives for shorter periods of time than in years with intermediate sea-ice cover. Our study therefore suggests that sea-ice cover is likely to affect the reproductive performance of Adélie penguins through its effects on foraging behaviour, as breeding success and most diving parameters share a common optimum. Some years, however, deviated from this general trend, suggesting that other factors (e.g. precipitation during the breeding season) might sometimes become preponderant over the sea-ice effects on breeding and foraging performance. Our study highlights the value of monitoring fitness parameters and individual behaviour concomitantly over the long-term to better characterize optimal environmental conditions and potential resilience of wildlife. Such an approach is crucial if we want to anticipate the effects of environmental change on Antarctic penguin populations.

Global Monitoring of Persistent Organic Pollutants (POPs) Using Seabird Preen Gland Oil.

Situated at high positions on marine food webs, seabirds accumulate high concentrations of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), and hexachlorocyclohexanes (HCHs). Our previous studies proposed the usefulness of seabirds preen gland oil as a nondestructive biomonitoring tool. The present study applied this approach to 154 adult birds of 24 species collected from 11 locations during 2005-2016 to demonstrate the utility of preen gland oil as a tool for global monitoring POPs, i.e., PCBs, DDTs, and HCHs. Concentrations of the POPs were higher in the Northern Hemisphere than in the Southern Hemisphere. In particular, ∑20PCBs and∑DDTs were highly concentrated in European shags (Phalacrocorax aristotelis) and Japanese cormorants (Phalacrocorax capillatus), explainable by a diet of benthic fishes. Higher concentrations of γ-HCH were detected in species from the polar regions, possibly reflecting the recent exposure and global distillation of ∑HCHs. We examined the relationship between age and POP concentrations in preen gland oil from 20 male European shags, aged 3-16 years old. Concentrations and compositions of POPs were not related to age. We also examined sex differences in the POP concentrations from 24 streaked shearwaters (Calonectris leucomelas) and did not detect a sex bias. These results underline the importance of the geographic concentration patterns and the dietary behavior as determinants species-specific POPs concentrations in preen gland oil.

The CCR4-NOT deadenylase activity contributes to generation of induced pluripotent stem cells.

Somatic cells can be reprogrammed as induced pluripotent stem cells (iPSCs) by introduction of the transcription factors, OCT3/4, KLF4, SOX2, and c-MYC. The CCR4-NOT complex is the major deadenylase in eukaryotes. Its subunits Cnot1, Cnot2, and Cnot3 maintain pluripotency and self-renewal of mouse and human embryonic stem (ES) cells and contribute to the transition from partial to full iPSCs. However, little is known about how the CCR4-NOT complex post-transcriptionally regulates the reprogramming process. Here, we show that the CCR4-NOT deadenylase subunits Cnot6, Cnot6l, Cnot7, and Cnot8, participate in regulating iPSC generation. Cnot1 knockdown suppresses expression levels of Cnot6, Cnot6l, Cnot7, and Cnot8 in mouse embryonic fibroblasts (MEFs) and decreases the number of alkaline phosphatase (ALP)-positive colonies after iPSC induction. Intriguingly, Cnot1 depletion allows Eomes and p21 mRNAs to persist, increasing their expression levels. Both mRNAs have longer poly(A) tails in Cnot1-depleted cells. Conversely, forced expression of a combination of Cnot6, Cnot6l, Cnot7, and Cnot8 increases the number of ALP-positive colonies after iPSC induction and decreases expression levels of Eomes and p21 mRNAs. Based on these observations, we propose that the CCR4-NOT deadenylase activity contributes to iPSC induction.