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Disruption of Myd88 in a salmonid epithelioid cell line reveals its contribution to bacterial detection and immune response
No full textInternational audienceToll-like receptors (TLRs) are a class of pattern-recognition receptors that recognize pathogenand damage-associated molecular patterns and initiate immune responses. TLRs selectively recruit distinct adapter molecules such as the myeloid differentiation primary response protein 88 (MyD88) that mediates signaling downstream of all TLRs, with the exception of TLR3. To investigate TLR signaling pathways in fish, we engineered a knockout clonal epitheliod fish cell line, named MYD88C2, using CRISPR/Cas9-mediated genome editing to disrupt the myd88 gene. We characterized the phenotype of this cell line alongside a wild-type cell line through gene-expression profiling and reporter-gene analyses in the context of stimulation with heat-killed Vibrio anguillarum, heat-killed Escherichia coli, flagellin, zymosan, and inoculation with a panel of viruses. We demonstrate that the proinflammatory response to zymosan and flagellin, as measured through the induction of proinflammatory genes, was greatly reduced in the MYD88C2 cell line. The responsiveness to zymosan was found to be partially restored by transfecting the MYD88C2 cell line with a myd88-expression plasmid. In contrast, the loss of the myd88 gene had no impact on the cytopathic effect associated with the replication of Viral Hemorrhagic Septicemia Virus (VHSV), Infectious Haematopoietic Necrosis Virus (IHNV), Infectious Pancreatic Necrosis Virus (IPNV), Spring Viraemia of Carp Virus (SVCV) or Infectious Salmon Anemia Virus (ISAV). These findings highlight the critical role of MyD88 in mediating specific proinflammatory responses to bacterial and fungal stimuli, while its absence has no detectable impact on viral replication or cytopathogenicity in epithelioid fish cells under the conditions tested
Novel risk loci in LGI1-antibody encephalitis: genome-wide association study discovery and validation cohorts
No full textInternational audienceAbstract Encephalitis with antibodies to leucine-rich glioma-inactivated 1 (LGI1-Ab-E) is a common form of autoimmune encephalitis, presenting with seizures and neuropsychiatric changes, predominantly in older males. More than 90% of patients carry the human leukocyte antigen (HLA) class II allele, HLA-DRB1*07:01. However, this is also present in 25% of healthy controls. Therefore, we hypothesized the presence of additional genetic predispositions. In this genome-wide association study and meta-analysis, we studied a discovery cohort of 131 French LGI1-Ab-E and a validation cohort of 126 American, British and Irish LGI1-Ab-E patients, ancestry-matched to 2613 and 2538 European controls, respectively. Outside the known major HLA signal, we found two single nucleotide polymorphisms at genome-wide significance (P < 5 × 10−8), implicating PTPRD, a protein tyrosine phosphatase, and LINC00670, a non-protein coding RNA gene. Meta-analysis defined four additional non-HLA loci, including the protein coding COBL gene. Polygenic risk scores with and without HLA variants proposed a contribution of non-HLA loci. In silico network analyses suggested LGI1 and PTPRD-mediated interactions via the established receptors of LGI1, ADAM22 and ADAM23. Our results identify new genetic loci in LGI1-Ab-E. These findings present opportunities for mechanistic studies and offer potential markers of susceptibility, prognostics and therapeutic responses
Rethinking HLA-B27 Testing: What HLA-B27 Can— and Cannot—Tell Us
No full textInternational audienceHLA-B27: a cornerstone in spondyloarthritis Nearly 50 years after its discovery as a major genetic risk factor for spondyloarthritis (SpA), 1 the precise contribution of HLA-B27 to disease development and progression remains only partially understood. Proposed mechanisms include aberrant antigen presentation, misfolding-induced endoplasmic reticulum stress and modulation of innate immune responses.
Ecophysiological modeling of the impact of light intensity and quality on microalgal growth in outdoor high-density open ponds
No full textInternational audienceLight is a critical factor governing microalgal growth, with both intensity (photosynthetically active radiation, PAR) and spectral composition (wavelength distribution) exerting significant influence. In high-density open raceway ponds, light attenuation creates pronounced vertical gradients in both PAR and spectral quality, though the specific effects of spectral composition on phytoplankton growth remain insufficiently characterized. This investigation examined the combined impacts of light intensity, spectral quality, and temperature on Dunaliella salina cultivated in greenhouse-based raceway ponds under natural irradiance. Outdoor experiments spanned two seasonal conditions (winter and summer), with cultures exposed to four spectral treatments: raceways equipped with neutral, red, and green filters, along with an unfiltered control system.Experimental data were used to parameterize a growth model integrating light intensity, spectral quality, and temperature dependencies. The model reproduced biomass dynamics under all spectral conditions and seasons. Notably, when normalized for PAR and initial biomass, green light promoted superior biomass conversion efficiency—attributed to its enhanced vertical penetration in high-light conditions. These findings highlight the potential of spectral optimization in raceway cultivation systems. The model provides a valuable tool for selecting semi-transparent photovoltaic filters or colored panels to simultaneously enhance microalgal productivity and harness unused wavelengths for energy generation
Implementation of a Multi-resolution Analysis Method to Characterize Multi-Scale Wave Structures in Lidar Data
No full textInternational audienceThis study introduces a processing method based on multi-resolution analysis (MRA) to characterize the multi-scale structures of gravity waves (GWs) with vertical wavelengths less than 13 km in lidar vertical profiles of temperature and wind in the middle atmosphere. The MRA approach is evaluated against conventional techniques, including polynomial fitting, spectral filtering, and nighttime temporal averaging, and applied to a case study of GWs observed on November 20, 2023. Among these methods, MRA demonstrates superior performance by enhancing the signal-to-noise ratio through signal decomposition and selective filtering. This targeted filtering improves the detection and extraction of GW-induced perturbations, particularly for dominant vertical wavelengths around 5 km. In terms of GW potential energy (GWPE), the MRA-based method yields values comparable to those derived from the variance method, except at the stratopause, where it estimates nearly twice the GWPE. However, the variance-based estimate remains within the MRA-derived confidence interval, indicating good agreement. In contrast, the Butterworth low-pass filter produces energy densities an order of magnitude higher than the variance method, suggesting possible overestimation of perturbation amplitudes. Polynomial fitting and nighttime mean methods appear insensitive to small-scale GW structures near the stratopause, where wave dissipation may occur. Beyond energy estimation, the MRA method offers a distinct advantage for analyzing GW propagation and scale interactions due to its multi-scale decomposition capability. It reveals GW features and structures that remain obscured by common techniques, establishing it as a valuable tool for advancing the study of GW dynamics in the middle atmosphere
Quantifying the radiative effect of volcanic sulfate aerosols from the Hunga Tonga 2022 eruption with infrared satellite sounders.
No full textInternational audienceThe January 2022 eruption of the Hunga Tonga volcano located in the Southern Pacific Ocean, one of the most intense ever recorded, propelled a plume directly into the stratosphere to an altitude of up to 50 km and released around 0.4 Gg of sulfur dioxide (SO2) in the atmosphere [Zuo, 2022]. The SO2 initially released was rapidly converted to large amounts of sulfuric acid (H2SO4), significantly affecting the Earth’s radiation budget for months after the eruption [Zhu, 2022]. In this study, we exploit the spectrally resolved Outgoing Longwave Radiation (SR-OLR) dataset [Whitburn, 2020] derived from the Infrared Atmospheric Sounding Interferometer (IASI) on board the Metop-B and -C platforms to evaluate directly the radiative impact of the eruption with a specific focus on H2SO4. A spectral index (HRI) is developed to detect and map the IASI pixels affected by H2SO4 in the Southern Hemisphere during the first six months following the eruption. The SR-OLR corresponding to these pixels is then compared to a reference database of SR-OLR, without the signature of H2SO4, built from the years before the eruption representative of the diverse scenes (in terms of surface and atmospheric parameters) observed within the Earth-atmosphere system. This approach enables us to derive the longwave direct radiative effect (LW-DRE) of H2SO4. Although many studies already exist on the amounts of SO2 and H2SO4 released and on their radiative impact [Schroeber, 2024 ; Sellitto, 2024 ; Sicard, 2024], this is the first time that the radiative effect of the Hunga Tonga eruption is evaluated directly from the SR-OLR, without relying on any forward model. These results provide a valuable alternative for assessing the radiative impact of volcanic eruptions
NH3 point source emissions and lifetimes derived from 15 years of IASI observations
No full textInternational audienceAmmonia (NH3) is a short-lived atmospheric constituent with a lifetime of a few hours. Despite its devastating effects on air quality and the environment, its global concentration continues to increase. Knowledge of its diverse emission sources is crucial for guiding and implementing effective legislation. Particularly large NH3 emissions originate from animal feedlots and housings, and a variety of industries related to the production of e.g., synthetic fertilizers, coke, steel, and soda ash. Emissions from these super emitters are currently not well constrained in bottom-up inventories. Satellite measurements offer an attractive means for quantifying point sources. In this work, we present the latest version of the NH3 point source catalogue based on 15 years of IASI measurements. Over 750 hotspots were identified based on a wind-rotated supersampling technique that significantly increases the spatial resolution of the measurements beyond the native resolution of the sounder. These were subsequently categorized into 12 distinct source categories through careful study of visible imagery, publicly available inventories and various online sources. Specific region-dependent periods were excluded from the analysis to avoid the contributions of fires, enabling the identification of sources that are otherwise difficult to detect. Each source was classified based on its geographical extent into one of the following categories: point source, extended point source, or cluster of point sources. We estimated the atmospheric lifetimes and emissions for each, by fitting an Exponentially Modified Gaussian (EMG) function to the observed NH3 distributions. The results are analyzed as functions of geographical location, season, and source category. In addition, yearly emissions are derived and compared to those presented in the European Pollutant Release and Transfer Register (E-PRTR) for the sources in Europe. We quantify the uncertainty in our estimates by propagating uncertainties in the input parameters. This includes the systematic uncertainty originating from the satellite measurements and the uncertainty in the fitting parameters such as the fitting domain and the chosen reference wind speed. The estimated uncertainties are source-dependent and can therefore be used to identify the sources whose emissions and resulting NH3 residence time are tightly constrained, making these particularly useful for the evaluation of emission inventories
An Extensive, Consistent Time Series of Volcanic and Anthropogenic Sulfur Dioxide (SO2) from IASI
No full textInternational audienceAtmospheric sulfur dioxide (SO2) originates from both anthropogenic activities, such as fossil fuel combustion and smelting, as well as natural sources like eruptions and quiescent degassing of volcanoes. Once in the atmosphere, SO2 rapidly oxidizes into sulfuric acid and sulfate aerosols, contributing to air pollution at local and regional scales. The altitude of SO2 injection critically influences its lifetime, and environmental and climatic effects. In the low- and mid-troposphere, SO2 leads to acid rain and cloud modification, harming air quality and ecosystems. In the stratosphere, it forms sulfate aerosols that scatter solar radiation, cooling the Earth's surface and potentially altering global climate patterns for months/years. Nadir satellite sounders operating in the thermal infrared (TIR) and ultraviolet-visible (UV-Vis) spectra have been providing valuable measurements of SO2 vertical column densities (VCDs) for years. In particular, the Infrared Atmospheric Sounding Interferometer (IASI), aboard the Metop satellites, delivers bi-daily global observations and offers a reliable long-term dataset currently spanning 17 years (since 2007). We present a general algorithm for fast retrieval of both SO2 plume heights and VCDs from IASI measurements. Compared to previous works, this algorithm achieves higher accuracy of SO2 height retrieval for dense, saturated volcanic plumes, and enhanced sensitivity of the column product, especially in the lower troposphere and for weak SO2 abundance. We illustrate the robustness of the SO2 retrievals on case studies of volcanic and anthropogenic plumes, with comparisons against TROPOMI UV-Vis SO2 measurements, CALIPSO plume altitude data, and findings in the literature. Efforts were made to ensure product consistency across the full 2007–2024 period and between the three IASI instruments onboard Metop-A, -B, and -C. The resulting dataset offers an extensive, coherent record of SO2 altitude and VCDs, with the potential of supporting diverse research and air quality monitoring applications. We present the entire 17-year IASI time series of SO2, focusing on major eruptions, the most active volcanoes, and long-term trends over large anthropogenic SO2 sources
First estimates of Tropical Tropopause Cirrus lifetimes using balloon-borne lidar observations
No full textInternational audienceTropical tropopause layer (TTL) cirrus clouds play a key role in the Earth climate system, yet the relative role of the various processes shaping them remains poorly known. Characterizing the temporal evolution of cloudy structures from observations is essential to address this issue, but represents a challenge. Indeed, space- and air-borne platform are not well-suited for this task: moving much faster than the air, they only provide instantaneous snapshots. In boreal winter 2021-2022, two balloon-borne lidars flew over the Equatorial Pacific Ocean, slowly drifting above the clouds. We use those unique observations of truncated (nighttime only) lifetime distribution to quantify the underlying continuous distribution of cloud lifetime above this homogeneous region. While most clouds are short-lived (mean lifetime estimated at about 6 h, a median value of 1 h), the temporal cloud cover is still dominated by the few long-lived ones (24 h or more). These results are compared to cirrus lifetimes in ERA5 reanalysis, showing a fair agreement between the reanalysis and the observations, and demonstrating the value of our approach to evaluate cirrus representation in global models