Netrin-1 blockade inhibits tumour growth and EMT features in endometrial cancer.

Netrin-1 is upregulated in cancers as a protumoural mechanism1. Here we describe netrin-1 upregulation in a majority of human endometrial carcinomas (ECs) and demonstrate that netrin-1 blockade, using an anti-netrin-1 antibody (NP137), is effective in reduction of tumour progression in an EC mouse model. We next examined the efficacy of NP137, as a first-in-class single agent, in a Phase I trial comprising 14 patients with advanced EC. As best response we observed 8 stable disease (8 out of 14, 57.1%) and 1 objective response as RECIST v.1.1 (partial response, 1 out of 14 (7.1%), 51.16% reduction in target lesions at 6 weeks and up to 54.65% reduction during the following 6 months). To evaluate the NP137 mechanism of action, mouse tumour gene profiling was performed, and we observed, in addition to cell death induction, that NP137 inhibited epithelial-to-mesenchymal transition (EMT). By performing bulk RNA sequencing (RNA-seq), spatial transcriptomics and single-cell RNA-seq on paired pre- and on-treatment biopsies from patients with EC from the NP137 trial, we noted a net reduction in tumour EMT. This was associated with changes in immune infiltrate and increased interactions between cancer cells and the tumour microenvironment. Given the importance of EMT in resistance to current standards of care2, we show in the EC mouse model that a combination of NP137 with carboplatin-paclitaxel outperformed carboplatin-paclitaxel alone. Our results identify netrin-1 blockade as a clinical strategy triggering both tumour debulking and EMT inhibition, thus potentially alleviating resistance to standard treatments.

CB2 expression in mouse brain: from mapping to regulation in microglia under inflammatory conditions.

Since its detection in the brain, the cannabinoid receptor type 2 (CB2) has been considered a promising therapeutic target for various neurological and psychiatric disorders. However, precise brain mapping of its expression is still lacking. Using magnetic cell sorting, calibrated RT-qPCR and single-nucleus RNAseq, we show that CB2 is expressed at a low level in all brain regions studied, mainly by few microglial cells, and by neurons in an even lower proportion. Upon lipopolysaccharide stimulation, modeling neuroinflammation in non-sterile conditions, we demonstrate that the inflammatory response is associated with a transient reduction in CB2 mRNA levels in brain tissue, particularly in microglial cells. This result, confirmed in the BV2 microglial cell line, contrasts with the positive correlation observed between CB2 mRNA levels and the inflammatory response upon stimulation by interferon-gamma, modeling neuroinflammation in sterile condition. Discrete brain CB2 expression might thus be up- or down-regulated depending on the inflammatory context.

Spatial Transcriptomics Reveal Pitfalls and Opportunities for the Detection of Rare High-Plasticity Breast Cancer Subtypes.

Breast cancer is one of the most prominent types of cancers, in which therapeutic resistance is a major clinical concern. Specific subtypes, such as claudin-low and metaplastic breast carcinoma (MpBC), have been associated with high nongenetic plasticity, which can facilitate resistance. The similarities and differences between these orthogonal subtypes, identified by molecular and histopathological analyses, respectively, remain insufficiently characterized. Furthermore, adequate methods to identify high-plasticity tumors to better anticipate resistance are lacking. Here, we analyzed 11 triple-negative breast tumors, including 3 claudin-low and 4 MpBC, via high-resolution spatial transcriptomics. We combined pathological annotations and deconvolution approaches to precisely identify tumor spots, on which we performed signature enrichment, differential expression, and copy number analyses. We used The Cancer Genome Atlas and Cancer Cell Line Encyclopedia public databases for external validation of expression markers. By focusing our spatial transcriptomic analyses on tumor cells in MpBC samples, we bypassed the negative impact of stromal contamination and identified specific markers that are neither expressed in other breast cancer subtypes nor expressed in stromal cells. Three markers (BMPER, POPDC3, and SH3RF3) were validated in external expression databases encompassing bulk tumor material and stroma-free cell lines. We unveiled that existing bulk expression signatures of high-plasticity breast cancers are relevant in mesenchymal transdifferentiated compartments but can be hindered by abundant stromal cells in tumor samples, negatively impacting their clinical applicability. Spatial transcriptomic analyses constitute powerful tools to identify specific expression markers and could thus enhance diagnosis and clinical care of rare high-plasticity breast cancers.

Comparative genomic analysis identifies small open reading frames (sORFs) with peptide-encoding features in avian 16S rDNA.

The mitochondrial genome (mt-DNA) functional repertoire has recently been enriched in mammals by the identification of functional small open reading frames (sORFs) embedded in ribosomal DNAs. Through comparative genomic analyses the presence of putatively functional sORFs was investigated in birds. Alignment of available avian mt-DNA sequences revealed highly conserved regions containing four putative sORFs that presented low insertion/deletion polymorphism rate (<0.1%) and preserved in frame start/stop codons in >80% of species. Detected sORFs included avian homologs of human Humanin and Short-Humanin-Like-Peptide 6 and two new sORFs not yet described in mammals. The amino-acid sequences of the four putative encoded peptides were strongly conserved among birds, with amino-acid p-distances (5.6 to 25.4%) similar to those calculated for typical avian mt-DNA-encoded proteins (14.8%). Conservation resulted from either drastic conservation of the nucleotide sequence or negative selection pressure. These data extend to birds the possibility that mitochondrial rDNA may encode small bioactive peptides.

What modulates animal longevity? Fast and slow aging in bivalves as a model for the study of lifespan.

Delineating the physiological and biochemical causes of aging process in the animal kingdom is a highly active area of research not only because of potential benefits for human health but also because aging process is related to life history strategies (growth and reproduction) and to responses of organisms to environmental conditions and stress. In this synthesis, we advocate studying bivalve species as models for revealing the determinants of species divergences in maximal longevity. This taxonomic group includes the longest living metazoan on earth (Arctica islandica), which insures the widest range of maximum life span when shorter living species are also included in the comparative model. This model can also be useful for uncovering factors modulating the pace of aging in given species by taking advantages of the wide disparity of lifespan among different populations of the same species. For example, maximal lifespan in different populations of A islandica range from approximately 36 years to over 500 years. In the last 15 years, research has revealed that either regulation or tolerance to oxidative stress is tightly correlated to longevity in this group which support further investigations on this taxon to unveil putative mechanistic links between Reactive Oxygen Species and aging process.

A Distinct Mitochondrial Genome with DUI-Like Inheritance in the Ocean Quahog Arctica islandica.

Mitochondrial DNA (mtDNA) is strictly maternally inherited in metazoans. The major exception to this rule has been found in many bivalve species which allow the presence of different sex-linked mtDNA molecules. This mechanism, named doubly uniparental inheritance (DUI), is characterized by the presence of two mtDNAs: The female mtDNA is found in somatic tissue and female gonads, whereas the male mtDNA is usually found in male gonads and sperm. In this study we highlight the existence of two divergent mitochondrial haplotypes with a low genetic difference around 6-8% in Arctica islandica, a long-lived clam belonging to the Arcticidae, a sister group to the Veneridae in which DUI has been found. Phylogenetic analysis on cytochrome b and 16S sequences from somatic and gonadic tissues of clams belonging to different populations reveals the presence of the "divergent" type in male gonads only and the "normal" type in somatic tissues and female gonads. This peculiar segregation of divergent mtDNA types speaks for the occurrence of the DUI mechanism in A. islandica. This example also highlights the difficulties to assess the presence of such particular mitochondrial inheritance system and underlines the possible misinterpretations in phylogeographic and phylogenetic studies of bivalve species linked to the presence of two poorly differentiated mitochondrial genomes.

NF-κB subunits RelA and c-Rel selectively control CD4+ T cell function in multiple sclerosis and cancer.

The outcome of cancer and autoimmunity is often dictated by the effector functions of CD4+ conventional T cells (Tconv). Although activation of the NF-κB signaling pathway has long been implicated in Tconv biology, the cell-autonomous roles of the separate NF-κB transcription-factor subunits are unknown. Here, we dissected the contributions of the canonical NF-κB subunits RelA and c-Rel to Tconv function. RelA, rather than c-Rel, regulated Tconv activation and cytokine production at steady-state and was required for polarization toward the TH17 lineage in vitro. Accordingly, RelA-deficient mice were fully protected against neuroinflammation in a model of multiple sclerosis due to defective transition to a pathogenic TH17 gene-expression program. Conversely, Tconv-restricted ablation of c-Rel impaired their function in the microenvironment of transplanted tumors, resulting in enhanced cancer burden. Moreover, Tconv required c-Rel for the response to PD-1-blockade therapy. Our data reveal distinct roles for canonical NF-κB subunits in different disease contexts, paving the way for subunit-targeted immunotherapies.

BMP2 and BMP7 cooperate with H3.3K27M to promote quiescence and invasiveness in pediatric diffuse midline gliomas.

Pediatric diffuse midline gliomas (pDMG) are an aggressive type of childhood cancer with a fatal outcome. Their major epigenetic determinism has become clear, notably with the identification of K27M mutations in histone H3. However, the synergistic oncogenic mechanisms that induce and maintain tumor cell phenotype have yet to be deciphered. In 20 to 30% of cases, these tumors have an altered BMP signaling pathway with an oncogenic mutation on the BMP type I receptor ALK2, encoded by ACVR1. However, the potential impact of the BMP pathway in tumors non-mutated for ACVR1 is less clear. By integrating bulk, single-cell, and spatial transcriptomic data, we show here that the BMP signaling pathway is activated at similar levels between ACVR1 wild-type and mutant tumors and identify BMP2 and BMP7 as putative activators of the pathway in a specific subpopulation of cells. By using both pediatric isogenic glioma lines genetically modified to overexpress H3.3K27M and patients-derived DIPG cell lines, we demonstrate that BMP2/7 synergizes with H3.3K27M to induce a transcriptomic rewiring associated with a quiescent but invasive cell state. These data suggest a generic oncogenic role for the BMP pathway in gliomagenesis of pDMG and pave the way for specific targeting of downstream effectors mediating the K27M/BMP crosstalk.

snPATHO-seq, a versatile FFPE single-nucleus RNA sequencing method to unlock pathology archives.

Formalin-fixed paraffin-embedded (FFPE) samples are valuable but underutilized in single-cell omics research due to their low RNA quality. In this study, leveraging a recent advance in single-cell genomic technology, we introduce snPATHO-seq, a versatile method to derive high-quality single-nucleus transcriptomic data from FFPE samples. We benchmarked the performance of the snPATHO-seq workflow against existing 10x 3' and Flex assays designed for frozen or fresh samples and highlighted the consistency in snRNA-seq data produced by all workflows. The snPATHO-seq workflow also demonstrated high robustness when tested across a wide range of healthy and diseased FFPE tissue samples. When combined with FFPE spatial transcriptomic technologies such as FFPE Visium, the snPATHO-seq provides a multi-modal sampling approach for FFPE samples, allowing more comprehensive transcriptomic characterization.

Spatial Transcriptomics Reveals Signatures of Histopathological Changes in Muscular Sarcoidosis.

Sarcoidosis is a multisystemic disease characterized by non-caseating granuloma infiltrating various organs. The form with symptomatic muscular involvement is called muscular sarcoidosis. The impact of immune cells composing the granuloma on the skeletal muscle is misunderstood. Here, we investigated the granuloma-skeletal muscle interactions through spatial transcriptomics on two patients affected by muscular sarcoidosis. Five major transcriptomic clusters corresponding to perigranuloma, granuloma, and three successive muscle tissue areas (proximal, intermediate, and distal) around the granuloma were identified. Analyses revealed upregulated pathways in the granuloma corresponding to the activation of T-lymphocytes and monocytes/macrophages cytokines, the upregulation of extracellular matrix signatures, and the induction of the TGF-ß signaling in the perigranuloma. A comparison between the proximal and distal muscles to the granuloma revealed an inverse correlation between the distance to the granuloma and the upregulation of cellular response to interferon-γ/α, TNF-α, IL-1,4,6, fibroblast proliferation, epithelial to mesenchymal cell transition, and the downregulation of muscle gene expression. These data shed light on the intercommunications between granulomas and the muscle tissue and provide pathophysiological mechanisms by showing that granuloma immune cells have a direct impact on proximal muscle tissue by promoting its progressive replacement by fibrosis via the expression of pro-inflammatory and profibrosing signatures. These data could possibly explain the evolution towards a state of disability for some patients.

MDR1-EXPRESSING CD4+ T CELLS WITH TH1.17 FEATURES RESIST TO NEOADJUVANT CHEMOTHERAPY AND ARE ASSOCIATED WITH BREAST CANCER CLINICAL RESPONSE.

BACKGROUND: Multidrug resistance-1 (MDR1) transporter limits the intracellular accumulation of chemotherapies (paclitaxel, anthracyclines) used in breast cancer (BC) treatment. In addition to tumor cells, MDR1 is expressed on immune cell subsets in which it confers chemoresistance. Among human T cells, MDR1 is expressed by most CD8+ T cells, and a subset of CD4+ T helper (Th) cells. Here we explored the expression, function and regulation of MDR1 on CD4+ T cells and investigated the role of this population in response to neoadjuvant chemotherapy (NAC) in BC. METHODS: Phenotypic and functional characteristics of MDR1+ CD4 Th cells were assessed on blood from healthy donors and patients with BC by flow cytometry. These features were extended to CD4+ Th cells from untreated breast tumor by flow cytometry and RNA-sequencing (RNA-seq). We performed in vitro polarization assays to decipher MDR1 regulation on CD4 Th cells. We evaluated in vitro the impact of chemotherapy agents on MDR1+ CD4+ Th cells. We analyzed the impact of NAC treatment on MDR1+ CD4+ Th cells from blood and tumors and their association with treatment efficacy in two independent BC cohorts and in a public RNA-seq data set of BC tumor biopsies before and after NAC. Finally, we performed single cell (sc) RNAseq of blood CD4+ memory T cells from NAC-treated patients and combined them with an scRNAseq public data set. RESULTS: MDR1+ CD4 Th cells were strongly enriched in Th1.17 polyfunctional cells but also in Th17 cells, both in blood and untreated breast tumor tissues. Mechanistically, Tumor growth factor (TGF)-ß1 was required for MDR1 induction during in vitro Th17 or Th1.17 polarization. MDR1 expression conferred a selective advantage to Th1.17 and Th17 cells following paclitaxel treatment in vitro and in vivo in NAC-treated patients. scRNAseq demonstrated MDR1 association with tumor Th1.17 and Th with features of cytotoxic cells. Enrichment in MDR1+ CD4+ Th1.17 and Th17 cells, in blood and tumors positively correlated with pathological response. Absence of early modulation of Th1.17 and Th17 in NAC-resistant patients, argue for its use as a biomarker for chemotherapy regimen adjustment. CONCLUSION: MDR1 favored the enrichment of Th1.17 and Th17 in blood and tumor after NAC that correlated to clinical response.

Fusion-negative rhabdomyosarcoma 3D organoids to predict effective drug combinations: A proof-of-concept on cell death inducers.

Rhabdomyosarcoma (RMS) is the main form of pediatric soft-tissue sarcoma. Its cure rate has not notably improved in the last 20 years following relapse, and the lack of reliable preclinical models has hampered the design of new therapies. This is particularly true for highly heterogeneous fusion-negative RMS (FNRMS). Although methods have been proposed to establish FNRMS organoids, their efficiency remains limited to date, both in terms of derivation rate and ability to accurately mimic the original tumor. Here, we present the development of a next-generation 3D organoid model derived from relapsed adult and pediatric FNRMS. This model preserves the molecular features of the patients' tumors and is expandable for several months in 3D, reinforcing its interest to drug combination screening with longitudinal efficacy monitoring. As a proof-of-concept, we demonstrate its preclinical relevance by reevaluating the therapeutic opportunities of targeting apoptosis in FNRMS from a streamlined approach based on transcriptomic data exploitation.

Selective upregulation of lipid metabolism in skeletal muscle of foraging juvenile king penguins: an integrative study.

The passage from shore to marine life of juvenile penguins represents a major energetic challenge to fuel intense and prolonged demands for thermoregulation and locomotion. Some functional changes developed at this crucial step were investigated by comparing pre-fledging king penguins with sea-acclimatized (SA) juveniles (Aptenodytes patagonicus). Transcriptomic analysis of pectoralis muscle biopsies revealed that most genes encoding proteins involved in lipid transport or catabolism were upregulated, while genes involved in carbohydrate metabolism were mostly downregulated in SA birds. Determination of muscle enzymatic activities showed no changes in enzymes involved in the glycolytic pathway, but increased 3-hydroxyacyl-CoA dehydrogenase, an enzyme of the ß-oxidation pathway. The respiratory rates of isolated muscle mitochondria were much higher with a substrate arising from lipid metabolism (palmitoyl-L-carnitine) in SA juveniles than in terrestrial controls, while no difference emerged with a substrate arising from carbohydrate metabolism (pyruvate). In vivo, perfusion of a lipid emulsion induced a fourfold larger thermogenic effect in SA than in control juveniles. The present integrative study shows that fuel selection towards lipid oxidation characterizes penguin acclimatization to marine life. Such acclimatization may involve thyroid hormones through their nuclear beta receptor and nuclear coactivators.

Extreme mitochondrial DNA divergence underlies genetic conflict over sex determination.

Cytoplasmic male sterility (CMS) is a form of genetic conflict over sex determination that results from differences in modes of inheritance between genomic compartments.1-3 Indeed, maternally transmitted (usually mitochondrial) genes sometimes enhance their transmission by suppressing the male function in a hermaphroditic organism to the detriment of biparentally inherited nuclear genes. Therefore, these hermaphrodites become functionally female and may coexist with regular hermaphrodites in so-called gynodioecious populations.3 CMS has been known in plants since Darwin's times4 but is previously unknown in the animal kingdom.5-8 We relate the first observation of CMS in animals. It occurs in a freshwater snail population, where some individuals appear unable to sire offspring in controlled crosses and show anatomical, physiological, and behavioral characters consistent with a suppression of the male function. Male sterility is associated with a mitochondrial lineage that underwent a spectacular acceleration of DNA substitution rates, affecting the entire mitochondrial genome-this acceleration concerns both synonymous and non-synonymous substitutions and therefore results from increased mitogenome mutation rates. Consequently, mitochondrial haplotype divergence within the population is exceptionally high, matching that observed between snail taxa that diverged 475 million years ago. This result is reminiscent of similar accelerations in mitogenome evolution observed in plant clades where gynodioecy is frequent,9,10 both being consistent with arms-race evolution of genome regions implicated in CMS.11,12 Our study shows that genomic conflicts can trigger independent evolution of similar sex-determination systems in plants and animals and dramatically accelerate molecular evolution.

Göttingen Minipigs as a Model to Evaluate Longevity, Functionality, and Memory of Immune Response Induced by Pertussis Vaccines.

Evaluation of the short-term and long-term immunological responses in a preclinical model that simulates the targeted age population with a relevant vaccination schedule is essential for human vaccine development. A Göttingen minipig model was assessed, using pertussis vaccines, to demonstrate that vaccine antigen-specific humoral and cellular responses, including IgG titers, functional antibodies, Th polarization and memory B cells can be assessed in a longitudinal study. A vaccination schedule of priming with a whole cell (DTwP) or an acellular (DTaP) pertussis vaccine was applied in neonatal and infant minipigs followed by boosting with a Tdap acellular vaccine. Single cell RNAsequencing was used to explore the long-term maintenance of immune memory cells and their functionality for the first time in this animal model. DTaP but not DTwP vaccination induced pertussis toxin (PT) neutralizing antibodies. The cellular immune response was also characterized by a distinct Th polarization, with a Th-2-biased response for DTaP and a Th-1/Th-17-biased response for DTwP. No difference in the maintenance of pertussis-specific memory B cells was observed in DTaP- or DTwP-primed animals 6 months post Tdap boost. However, an increase in pertussis-specific T cells was still observed in DTaP primed minipigs, together with up-regulation of genes involved in antigen presentation and interferon pathways. Overall, the minipig model reproduced the humoral and cellular immune responses induced in humans by DTwP vs. DTaP priming, followed by Tdap boosting. Our data suggest that the Göttingen minipig is an attractive preclinical model to predict the long-term immunogenicity of human vaccines against Bordetella pertussis and potentially also vaccines against other pathogens.

Presence of male mitochondria in somatic tissues and their functional importance at the whole animal level in the marine bivalve Arctica islandica.

Metazoans normally possess a single lineage of mitochondria inherited from the mother (♀-type mitochondria) while paternal mitochondria are absent or eliminated in fertilized eggs. In doubly uniparental inheritance (DUI), which is specific to the bivalve clade including the ocean quahog, Arctica islandica, ♂-type mitochondria are retained in male gonads and, in a few species, small proportions of ♂-type mitochondria co-exist with ♀-type in somatic tissues. To the best of our knowledge, we report, for the first time in metazoan, the natural occurrence of male and female individuals with exclusively ♂-type mitochondria in somatic tissues of the bivalve A. islandica. Mitochondrial genomes differ by ~5.5% at DNA sequence level. Exclusive presence of ♂-type mitochondria affects mitochondrial complexes partially encoded by mitochondrial genes and leads to a sharp drop in respiratory capacity. Through a combination of whole mitochondrial genome sequencing and molecular assays (gene presence and expression), we demonstrate that 1) 11% of individuals of an Icelandic population appear homoplasmic for ♂-type mitochondria in somatic tissues, 2) ♂-type mitochondrial genes are transcribed and 3) individuals with ♂-type mitochondria in somatic cells lose 30% of their wild-type respiratory capacity. This mitochondrial pattern in A. islandica is a special case of DUI, highlighted in individuals from both sexes with functional consequences at cellular and conceivably whole animal level.

Transcriptome analysis in non-model species: a new method for the analysis of heterologous hybridization on microarrays.

BACKGROUND: Recent developments in high-throughput methods of analyzing transcriptomic profiles are promising for many areas of biology, including ecophysiology. However, although commercial microarrays are available for most common laboratory models, transcriptome analysis in non-traditional model species still remains a challenge. Indeed, the signal resulting from heterologous hybridization is low and difficult to interpret because of the weak complementarity between probe and target sequences, especially when no microarray dedicated to a genetically close species is available. RESULTS: We show here that transcriptome analysis in a species genetically distant from laboratory models is made possible by using MAXRS, a new method of analyzing heterologous hybridization on microarrays. This method takes advantage of the design of several commercial microarrays, with different probes targeting the same transcript. To illustrate and test this method, we analyzed the transcriptome of king penguin pectoralis muscle hybridized to Affymetrix chicken microarrays, two organisms separated by an evolutionary distance of approximately 100 million years. The differential gene expression observed between different physiological situations computed by MAXRS was confirmed by real-time PCR on 10 genes out of 11 tested. CONCLUSIONS: MAXRS appears to be an appropriate method for gene expression analysis under heterologous hybridization conditions.

Mitochondrial Traits Previously Associated With Species Maximum Lifespan Do Not Correlate With Longevity Across Populations of the Bivalve Arctica islandica.

The mitochondrial oxidative stress theory of aging posits that membrane susceptibility to peroxidation and the organization of the electron transport system (ETS) linked with reactive oxygen species (ROS) generation are two main drivers of lifespan. While a clear correlation has been established from species comparative studies, the significance of these characteristics as potential modulators of lifespan divergences among populations of individual species is still to be tested. The bivalve Arctica islandica, the longest-lived non-colonial animal with a record lifespan of 507 years, possesses a lower mitochondrial peroxidation index (PI) and reduced H2O2 efflux linked to complexes I and III activities than related species. Taking advantage of the wide variation in maximum reported longevities (MRL) among 6 European populations (36-507 years), we examined whether these two mitochondrial properties could explain differences in longevity. We report no relationship between membrane PI and MRL in populations of A. islandica, as well as a lack of intraspecific relationship between ETS complex activities and MRL. Individuals from brackish sites characterized by wide temperature and salinity windows had, however, markedly lower ETS enzyme activities relative to citrate synthase activity. Our results highlight environment-dependent remodeling of mitochondrial phenotypes.

Transcriptomic data analysis and differential gene expression of antioxidant pathways in king penguin juveniles (Aptenodytes patagonicus) before and after acclimatization to marine life.

In this article, we present differentially expressed gene profiles in the pectoralis muscle of wild juvenile king penguins that were either naturally acclimated to cold marine environment or experimentally immersed in cold water as compared with penguin juveniles that never experienced cold water immersion. Transcriptomic data were obtained by hybridizing penguins total cDNA on Affymetrix GeneChip Chicken Genome arrays and analyzed using maxRS algorithm, "Transcriptome analysis in non-model species: a new method for the analysis of heterologous hybridization on microarrays" (Dégletagne et al., 2010) [1]. We focused on genes involved in multiple antioxidant pathways. For better clarity, these differentially expressed genes were clustered into six functional groups according to their role in controlling redox homeostasis. The data are related to a comprehensive research study on the ontogeny of antioxidant functions in king penguins, "Hormetic response triggers multifaceted anti-oxidant strategies in immature king penguins (Aptenodytes patagonicus)" (Rey et al., 2016) [2]. The raw microarray dataset supporting the present analyses has been deposited at the Gene Expression Omnibus (GEO) repository under accessions GEO: GSE17725 and GEO: GSE82344.

Hormetic response triggers multifaceted anti-oxidant strategies in immature king penguins (Aptenodytes patagonicus).

Repeated deep dives are highly pro-oxidative events for air-breathing aquatic foragers such as penguins. At fledging, the transition from a strictly terrestrial to a marine lifestyle may therefore trigger a complex set of anti-oxidant responses to prevent chronic oxidative stress in immature penguins but these processes are still undefined. By combining in vivo and in vitro approaches with transcriptome analysis, we investigated the adaptive responses of sea-acclimatized (SA) immature king penguins (Aptenodytes patagonicus) compared with pre-fledging never-immersed (NI) birds. In vivo, experimental immersion into cold water stimulated a higher thermogenic response in SA penguins than in NI birds, but both groups exhibited hypothermia, a condition favouring oxidative stress. In vitro, the pectoralis muscles of SA birds displayed increased oxidative capacity and mitochondrial protein abundance but unchanged reactive oxygen species (ROS) generation per g tissue because ROS production per mitochondria was reduced. The genes encoding oxidant-generating proteins were down-regulated in SA birds while mRNA abundance and activity of the main antioxidant enzymes were up-regulated. Genes encoding proteins involved in repair mechanisms of oxidized DNA or proteins and in degradation processes were also up-regulated in SA birds. Sea life also increased the degree of fatty acid unsaturation in muscle mitochondrial membranes resulting in higher intrinsic susceptibility to ROS. Oxidative damages to protein or DNA were reduced in SA birds. Repeated experimental immersions of NI penguins in cold-water partially mimicked the effects of acclimatization to marine life, modified the expression of fewer genes related to oxidative stress but in a similar way as in SA birds and increased oxidative damages to DNA. It is concluded that the multifaceted plasticity observed after marine life may be crucial to maintain redox homeostasis in active tissues subjected to high pro-oxidative pressure in diving birds. Initial immersions in cold-water may initiate an hormetic response triggering essential changes in the adaptive antioxidant response to marine life.