Genome-wide comparative methylation analysis reveals the fate of germ stem cells after surrogate production in teleost.

BACKGROUND: Surrogate production by germline stem cell transplantation is a powerful method to produce donor-derived gametes via a host, a practice known as surrogacy. The gametes produced by surrogates are often analysed on the basis of their morphology and species-specific genotyping, which enables conclusion to be drawn about the donor's characteristics. However, in-depth information, such as data on epigenetic changes, is rarely acquired. Germ cells develop in close contact with supporting somatic cells during gametogenesis in vertebrates, and we hypothesize that the recipient's gonadal environment may cause epigenetic changes in produced gametes and progeny. Here, we extensively characterize the DNA methylome of donor-derived sperm and their intergenerational effects in both inter- and intraspecific surrogates. RESULTS: We found more than 3000 differentially methylated regions in both the sperm and progeny derived from inter- and intraspecific surrogates. Hypermethylation in the promoter regions of the protocadherin gamma gene in the intraspecific surrogates was found to be associated with germline transmission. On the contrary, gene expression level and the embryonic development of the offspring remained unaffected. We also discovered MAPK/p53 pathway disruption in interspecific surrogates due to promoter hypermethylation and identified that the inefficient removal of meiotic-arrested endogenous germ cells in hybrid gonads led to the production of infertile spermatozoa. CONCLUSIONS: Donor-derived sperm and progeny from inter- and intraspecific surrogates were more globally hypermethylated than those of the donors. The observed changes in DNA methylation marks in the surrogates had no significant phenotypic effects in the offspring.

JAK inhibitors in refractory juvenile rheumatic diseases: Efficacy, tolerance and type-I interferon profiling, a single center retrospective study.

OBJECTIVES: - Janus Kinase inhibitors (JAKi) are a new class of drugs available for pediatric rheumatic diseases. This study aimed to describe the safety and effectiveness of JAKi in these diseases, with a focus on longitudinal interferon-stimulated genes (ISG) assessment. METHODS: - We present a single-center retrospective study of children with refractory pediatric rheumatic diseases including connective tissue diseases, monogenic type I interferonopathies or juvenile idiopathic arthritis, receiving JAKi. According to physicians' assessment, treatment effectiveness was classified at 12 months as a complete response in the total absence of disease activity, partial response in case of significant (>50%) but incomplete improvement or no response in the case of non-response or improvement of less than 50% of the clinical and biological parameters. ISG were monitored longitudinally using Nanostring technology. RESULTS: - 22 children were retrospectively included in this study, treated either by baricitinib or ruxolitinib. Complete response was achieved at 12 months in 9/22 (41%) patients. 6/22 (27%) patients were non-responders and treatment had been discontinued in five of them. Within the interferon (IFN)-related diseases group, ISG-score was significantly reduced 12 months after JAKi onset (p = 0.0068). At 12 months, daily glucocorticoid doses had been reduced with a median dose of 0.16 mg/kg/day (IQR 0.11; 0.33) (p = 0.0425). 7/22 (32%) patients had experienced side effects, infections being the most common. Increase of the body mass index was also recorded in children in the first 6 months of treatment. CONCLUSION: - JAKi represent a promising treatment of immune-mediated pediatric diseases, enabling to decrease type-I IFN transcriptomic signature in responding patients, especially in the context of juvenile dermatomyositis. JAKi represent steroid-sparing drugs but they induce metabolic changes linked to weight gain, posing a concern in the treatment of young patients and teenagers. More data are required to define the efficacy and safety of JAKi in the management of refractory pediatric rheumatic diseases.

Development of clinical and laboratory biomarkers in an international cohort of 428 children with lupus nephritis.

BACKGROUND: Lupus nephritis (LN) is a very severe manifestation of lupus. There is no consensus on which treatment goals should be achieved to protect kidney function in children with LN. METHODS: We retrospectively analyzed trends of commonly used laboratory biomarkers of 428 patients (≤ 18 years old) with biopsy-proven LN class ≥ III. We compared data of patients who developed stable kidney remission from 6 to 24 months with those who did not. RESULTS: Twenty-five percent of patients maintained kidney stable remission while 75% did not. More patients with stable kidney remission showed normal hemoglobin and erythrocyte sedimentation rate from 6 to 24 months compared to the group without stable kidney remission. eGFR ≥ 90 ml/min/1.73m2 at onset predicted the development of stable kidney remission (93.8%) compared to 64.7% in those without stable remission (P < 0.00001). At diagnosis, 5.9% and 20.2% of the patients showed no proteinuria in the group with and without stable kidney remission, respectively (P = 0.0001). dsDNA antibodies decreased from onset of treatment mainly during the first 3 months in all groups, but more than 50% of all patients in both groups never normalized after 6 months. Complement C3 and C4 increased mainly in the first 3 months in all patients without any significant difference. CONCLUSIONS: Normal eGFR and the absence of proteinuria at onset were predictors of stable kidney remission. Significantly more children showed normal levels of Hb and erythrocyte sedimentation rate (ESR) from 6 to 24 months in the group with stable kidney remission.

Conserved and divergent arms of the antiviral response in the duplicated genomes of salmonid fishes.

Antiviral innate immunity is orchestrated by the interferon system, which appeared in ancestors of jawed vertebrates. Interferon upregulation induces hundreds of interferon-stimulated-genes (ISGs) with effector or regulatory functions. Here we investigated the evolutionary diversification of ISG responses through comparison of two salmonid fishes, accounting for the impact of sequential whole genome duplications ancestral to teleosts and salmonids. We analysed the transcriptomic response of the IFN pathway in the head kidney of rainbow trout and Atlantic salmon, which separated 25-30 Mya. We identified a large set of ISGs conserved in both species and cross-referenced them with zebrafish and human ISGs. In contrast, around one-third of salmonid ISG lacked orthologs in human, mouse, chicken or frog, and often between rainbow trout and Atlantic salmon, revealing a fast-evolving, lineage-specific arm of the antiviral response. This study also provides a key resource for in-depth functional analysis of ISGs in salmonids of commercial significance.

Strengths and limitations of reduced representation bisulfite sequencing (RRBS) in the perspective of DNA methylation analysis in fish: a case-study on rainbow trout spermatozoa.

DNA methylation in CpG dinucleotides is an important epigenetic mark in fish spermatozoa since it has been shown that some sperm methylome features are transmitted to the offspring. Reduced representation bisulfite sequencing (RRBS) is one genome-scale methods developed to assess DNA methylation at CpG sites. It allows the sequencing of a reduced fraction of the genome expected to be enriched in CpGs. The aim of this study is to characterize the extent of the CpG sites that can be identified in the RRBS-reduced sequenced fraction of rainbow trout spermatozoa, in order to evaluate the potential of RRBS for sperm DNA methylation studies. We observed that RRBS did provide a reduced amount of genomic data, the sum of the CpGs analyzed on 12 males spanning 9% of the total genomic CpGs. CpGs were only slightly enriched in the RRBS data (×1.7 times the sequenced nucleotides), the possible causes being linked to trout genome structure and sequenced fragments size. All genomic functional features were represented in our CpG dataset, with a noticeable enrichment in exons but, strikingly, not in promoters. The number of CpGs shared between biological replicates was low, but this proportion reached workable values from six biological replicates (46% of the analyzed cytosines) on. The choices that are to be made regarding fragment size selection and the options during bioinformatic data processing are discussed. In all, RRBS is a relevant first-approach method to scan the CpG DNA methylation status of spermatozoa along rainbow trout genome, although in a very reduced pattern among biological replicates.

Extra-osseous manifestations in chronic recurrent multifocal osteomyelitis: a retrospective study.

OBJECTIVES: Extra-osseous (EO) manifestations are poorly characterized in chronic recurrent multifocal osteomyelitis (CRMO). This study aimed to further define the frequency, characteristics and treatment of EO events in CRMO and whether different phenotypes can be distinguished and benefit from special management. METHODS: This multicentre retrospective study included CRMO patients followed in several paediatric rheumatology departments in France, between 2015 and 2022. EO manifestations were defined as skin lesions, gastrointestinal manifestations, arthritis, enthesitis, sacroiliitis, uveitis, vasculitis, and fever. At the last visit, the physician defined CRMO as active in the presence of clinical manifestations including both osseous and EO symptoms. RESULTS: We included 133 patients; 87 (65.4%) were girls; the median age at first symptoms was 9.0 years (interquartile range 7.0-10.0). EO manifestations were described in 90 (67.7%) patients, with a predominance of skin lesions (n = 51/90; 56.7%), followed by sacroiliitis (n = 38/90; 42.2%), enthesitis (n = 21/90; 23.3%), arthritis (n = 14/90, 15.6%) and gastrointestinal manifestations (n = 6/90, 6.7%). The use of non-steroidal anti-inflammatory drugs and bisphosphonates did not differ by presence or not of EO manifestations. Biologics were taken more frequently by patients with than without EO manifestations (p< 0.001); tumour necrosis factor inhibitors were used in 33 (36.7%) EO+ patients. Under this treatment, 18 (54.5%) patients achieved complete remission of osseous and EO manifestations. At the last visit, more EO-positive than EO-negative patients were on treatment (p= 0.009), with active disease in 58 (64.4%) patients. CONCLUSION: The analysis of EO manifestations in CRMO delineates 2 groups of patients in terms of severity and treatments used. Our study opens up new pathophysiological leads that may underlie the wide range of CRMO phenotypes.

Higher Than Recommended Folic Acid Intakes is Associated with High Folate Status Throughout Pregnancy in a Prospective French-Canadian Cohort.

BACKGROUND: Folate and vitamin B12 status during pregnancy are important for maternal and neonatal health. Maternal intake and prepregnancy body mass index (ppBMI) can influence biomarker status. OBJECTIVES: This study aimed to, throughout pregnancy; 1) assess folate and B12 status including serum total folate, plasma total vitamin B12, and homocysteine (tHcy); 2) examine how these biomarkers are associated with intakes of folate and B12 and with ppBMI; and 3) determine predictors of serum total folate and plasma total vitamin B12. METHODS: In each trimester (T1, T2, and T3), food and supplement intakes of 79 French-Canadian pregnant individuals were assessed by 3 dietary recalls (R24W) and a supplement use questionnaire. Fasting blood samples were collected. Serum total folate and plasma total vitamin B12 and tHcy were assessed by immunoassay (Siemens ADVIA Centaur XP). RESULTS: Participants were 32.1 ± 3.7 y and had a mean ppBMI of 25.7 ± 5.8 kg/m2. Serum total folate concentrations were high (>45.3 nmol/L, T1: 75.4 ± 55.1, T2: 69.1 ± 44.8, T3: 72.1 ± 52.1, P = 0.48). Mean plasma total vitamin B12 concentrations were >220 pmol/L (T1: 428 ± 175, T2: 321 ± 116, T3: 336 ± 128, P < 0.0001). Mean tHcy concentrations were <11 µmol/L across trimesters. Most participants (79.6%-86.1%) had a total folic acid intake above the Tolerable Upper Intake Level (UL, >1000 µg/d). Supplement use accounted for 71.9%-76.1% and 35.3%-41.8% of total folic acid and vitamin B12 intakes, respectively. The ppBMI was not correlated with serum total folate (P > 0.1) but was weakly correlated with and predicted lower plasma total vitamin B12 in T3 (r = -0.23, P = 0.04; r2 = 0.08, standardized beta [sß] = -0.24, P = 0.01). Higher folic acid intakes from supplements predicted higher serum total folate (T1: r2 = 0.05, sß = 0.15, P = 0.04, T2: r2 = 0.28, sß = 0.56, P = 0.01, T3: r2 = 0.19, sß = 0.44, P < 0.0001). CONCLUSIONS: Most pregnant individuals had elevated serum total folate concentrations, reflecting total folic acid intakes above the UL driven by supplement use. Vitamin B12 concentrations were generally adequate and differed by ppBMI and pregnancy stage.

International cohort of 382 children with lupus nephritis - presentation, treatment and outcome at 24 months.

BACKGROUND: Children with lupus have a higher chance of nephritis and worse kidney outcome than adult patients. METHODS: We retrospectively analyzed clinical presentation, treatment and 24-month kidney outcome in a cohort of 382 patients (≤ 18 years old) with lupus nephritis (LN) class ≥ III diagnosed and treated in the last 10 years in 23 international centers. RESULTS: The mean age at onset was 11 years 9 months and 72.8% were females. Fifty-seven percent and 34% achieved complete and partial remission at 24-month follow-up, respectively. Patients with LN class III achieved complete remission more often than those with classes IV or V (mixed and pure). Only 89 of 351 patients maintained stable complete kidney remission from the 6th to 24th months of follow-up. eGFR ≥ 90 ml/min/1.73 m2 at diagnosis and biopsy class III were predictive of stable kidney remission. The youngest and the oldest age quartiles (2y-9y, 5m) (14y, 2m-18y,2m) showed lower rates of stable remission (17% and 20.7%, respectively) compared to the two other age groups (29.9% and 33.7%), while there was no difference in gender. No difference in achieving stable remission was found between children who received mycophenolate or cyclophosphamide as induction treatment. CONCLUSION: Our data show that the rate of complete remission in patients with LN is still not high enough. Severe kidney involvement at diagnosis was the most important risk factor for not achieving stable remission while different induction treatments did not impact outcome. Randomized treatment trials involving children and adolescents with LN are needed to improve outcome for these children. A higher resolution version of the Graphical abstract is available as Supplementary information.

Defining renal remission in an international cohort of 248 children and adolescents with lupus nephritis.

OBJECTIVE: We studied the rate of remission of LN in an international cohort of 248 children and adolescents with biopsy-proven LN. Five different definitions from scientific studies and the definitions recommended by the ACR and Kidney Disease: Improving Global Outcomes were used. METHODS: Anonymized clinical data in patients with biopsy-proven LN class ≥III (International Society of Nephrology/Royal Pathology Society) diagnosed and treated in the last 10 years in 23 international centres from 10 countries were collected. We compared the rate of patients in complete and partial remission applying the different definitions. RESULTS: The mean age at diagnosis was 11 years and 4 months, and 177 were females. The number of patients in complete and partial remission varied a great deal between the different definitions. At 24 months, between 50% and 78.8% of the patients were in full remission as defined by the different criteria. The number of patients in partial remission was low, between 2.3% and 25%. No difference in achieved remission was found between boys and girls or between children and adolescents (P > 0.05). Patients with East Asian ethnicity reached remission more often than other ethnicities (P = 0.03-0.0008). Patients treated in high-income countries showed a higher percentage of complete remission at 12 and 24 months (P = 0.002-0.000001). CONCLUSION: The rate of children and adolescents with LN achieving remission varied hugely with the definition used. Our results give important information for long-awaited treatment studies in children and young people.

The hydroxymethylome of multiple myeloma identifies FAM72D as a 1q21 marker linked to proliferation.

Cell identity relies on the cross-talk between genetics and epigenetics and their impact on gene expression. Oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) is the first step of an active DNA demethylation process occurring mainly at enhancers and gene bodies and, as such, participates in processes governing cell identity in normal and pathological conditions. Although genetic alterations are well documented in multiple myeloma (MM), epigenetic alterations associated with this disease have not yet been thoroughly analyzed. To gain insight into the biology of MM, genome-wide 5hmC profiles were obtained and showed that regions enriched in this modified base overlap with MM enhancers and super enhancers and are close to highly expressed genes. Through the definition of a MM-specific 5hmC signature, we identified FAM72D as a poor prognostic gene located on 1q21, a region amplified in high risk myeloma. We further uncovered that FAM72D functions as part of the FOXM1 transcription factor network controlling cell proliferation and survival and we evidenced an increased sensitivity of cells expressing high levels of FOXM1 and FAM72 to epigenetic drugs targeting histone deacetylases and DNA methyltransferases.

Differential DNA damage signalling and apoptotic threshold correlate with mouse epiblast-specific hypersensitivity to radiation.

Between implantation and gastrulation, mouse pluripotent epiblast cells expand enormously in number and exhibit a remarkable hypersensitivity to DNA damage. Upon low-dose irradiation, they undergo mitotic arrest followed by p53-dependent apoptosis, whereas the other cell types simply arrest. This protective mechanism, active exclusively after E5.5 and lost during gastrulation, ensures the elimination of every mutated cell before its clonal expansion and is therefore expected to greatly increase fitness. We show that the insurgence of apoptosis relies on the epiblast-specific convergence of both increased DNA damage signalling and stronger pro-apoptotic balance. Although upstream Atm/Atr global activity and specific γH2AX phosphorylation are similar in all cell types of the embryo, 53BP1 recruitment at DNA breaks is immediately amplified only in epiblast cells after ionizing radiation. This correlates with rapid epiblast-specific activation of p53 and its transcriptional properties. Moreover, between E5.5 and E6.5 epiblast cells lower their apoptotic threshold by enhancing the expression of pro-apoptotic Bak and Bim and repressing the anti-apoptotic Bcl-xL. Thus, even after low-dose irradiation, the cytoplasmic priming of epiblast cells allows p53 to rapidly induce apoptosis via a partially transcription-independent mechanism.

Familial Mediterranean fever mutations are hypermorphic mutations that specifically decrease the activation threshold of the Pyrin inflammasome.

Objectives: FMF is the most frequent autoinflammatory disease and is associated in most patients with bi-allelic MEFV mutations. MEFV encodes Pyrin, an inflammasome sensor activated following RhoGTPase inhibition. The functional consequences of MEFV mutations on the ability of Pyrin variants to act as inflammasome sensors are largely unknown. The aim of this study was to assess whether MEFV mutations affect the ability of Pyrin to detect RhoGTPase inhibition and other inflammasome stimuli. Methods: IL-1ß and IL-18 released by monocytes from healthy donors (HDs) and FMF patients were measured upon specific engagement of the Pyrin, NLRP3 and NLRC4 inflammasomes. Cell death kinetics following Pyrin activation was monitored in real time. Results: Monocytes from FMF patients secreted significantly more IL-1ß and IL-18 and died significantly faster than HD monocytes in response to low concentrations of Clostridium difficile toxin B (TcdB), a Pyrin-activating stimulus. Monocytes from patients bearing two MEFV exon 10 pathogenic variants displayed an increased Pyrin inflammasome response compared with monocytes from patients with a single exon 10 pathogenic variant indicating a gene-dosage effect. Using a short priming step, the response of monocytes from FMF patients to NLRP3- and NLRC4-activating stimuli was normal indicating that MEFV mutations trigger a specific hypersensitivity of monocytes to low doses of a Pyrin-engaging stimulus. Conclusion: Contrary to the NLRP3 mutations described in cryopyrin-associated periodic syndrome, FMF-associated MEFV mutations do not lead to a constitutive activation of Pyrin. Rather, FMF-associated mutations are hypermorphic mutations that specifically decrease the activation threshold of the Pyrin inflammasome without affecting other canonical inflammasomes.

Renal transplantation in children under 3 years of age: Experience from a single-center study.

RTx remains challenging in children under 3 years of age. This single-center study reviewed the medical records of children <3 years transplanted since 1987 (N = 32, Group 1). They were matched for donor type and RTx period with children aged 3-13 years (N = 32, Group 2) and 13-18 years (N = 32, Group 3). There were no between-group significant differences regarding distributions of gender, primary renal disease, proportion of dialysis before RTx, and growth (SDS). Compared to Groups 2 and 3, Group 1 had more peritoneal dialyses (P < .001), more EBV mismatches (P = .04), and longer warm ischemia times (P < .001). The risk of graft loss was not significantly different among age groups (hazard ratio, 2.4 in Group 2 and 2.0 in Group 3 vs Group 1; P = .2). Death occurred in four patients (3 in Group 1 and 1 in Group 2) and graft loss occurred in 28 patients, mainly due to chronic allograft nephropathy. In recipients <3 years of age, the outcomes of RTx are close to those obtained in older pediatric age groups. Thus, young patients may be transplanted in experienced multidisciplinary teams without additional risks provided that particular attention is paid to donor selection and prevention/early diagnosis of comorbidities and complications.

Clinical spectrum and outcome of Takayasu's arteritis in children.

OBJECTIVES: We aimed to compare clinical spectrum and outcome between adults and children with Takayasu's arteritis (TAK) in a European population. METHODS: We made a nationwide retrospective observational study between 1988 and 2019. All adult patients met the ACR diagnostic criteria for TAK and all children met the EULAR/PRINTO/PRES criteria for paediatric TAK. RESULTS: We identified 46 children and 389 adults with TAK. The male to female ratio was 34/46 (0.74) in the paediatric group compared to 241/274 (0.88) in the adult group (P<0.05). Children presented with significantly more systemic symptoms; i.e., fever (P<0.05), fatigue (P<0.001), weight loss (P<0.001), abdominal pain (P<0.05), and myalgia (P<0.05) while adults had more upper limb claudication (P<0.01). Topography of the lesions differed significantly between the two groups: adults had more damage at the cerebral vasculature (P<0.01), upper and lower limbs (P<0.001) while children had more kidney lesions (P<0.05). Children TAK had more frequent (P<0.01) and higher (P<0.001) biological inflammation than adults. Children received higher dose-weight of corticosteroids (P=0.001) and less biotherapy (P<0.010) at diagnosis. Relapses (P<0.05) and death (8.6% vs 4.9%) were more frequent in children TAK than in adults. CONCLUSION: Paediatric TAK seems more severe than adult TAK. Therefore, paediatrics patients may require closer monitoring and systemic use of biological treatment.

Attitudes and Behaviors towards Food and Weight in Late Pregnancy: A Comparative Approach between Individuals with and without Previous Bariatric Surgery.

The aims of this study were to compare, between pregnant individuals with and without bariatric surgery: (1) eating behaviors, (2) intuitive eating components and, (3) attitudes towards weight gain. This retrospective study included data collected in healthy pregnant individuals with and without previous bariatric surgery who were recruited at the Centre Hospitalier Universitaire (CHU) de Québec-Université Laval. Pregnant individuals who underwent bariatric surgery (biliopancreatic bypass with duodenal switch [n = 14] or sleeve gastrectomy [n = 5]) were individually matched, for age (±0.4 years) and body mass index (BMI) (±0.3 kg/m2), with pregnant individuals who have not received bariatric surgery. In the second trimester, participants completed the Three Factor Eating Questionnaire (TFEQ) and the Intuitive Eating Scale 2 (IES-2). In the third trimester, participants completed the French version of the Pregnancy Weight Gain Attitude Scale assessing attitudes towards weight gain. Pregnant individuals who have had bariatric surgery had a higher score for flexible restraint and a lower score for situational susceptibility to disinhibition compared to individuals who have not had undergone bariatric surgery (2.89 ± 1.15 vs. 1.95 ± 1.31; p = 0.04 and 1.11 ± 1.29 vs. 2.79 ± 1.44, respectively; p < 0.001). Regarding intuitive eating, pregnant individuals who experienced bariatric surgery had a higher score for reliance on internal hunger and satiety cues and a lower one for unconditional permission to eat compared with those who had not experienced bariatric surgery (3.99 ± 0.81 vs. 3.30 ± 1.03; p = 0.02 and 3.28 ± 0.54 vs. 3.61 ± 0.68, respectively; p = 0.03). No difference in attitudes towards weight gain was observed between groups. Overall, pregnant individuals who had undergone bariatric surgery had different eating behaviors and intuitive eating components compared to pregnant individuals without bariatric surgery. These results need to be confirmed in further studies with larger sample sizes.

The absence of Prep1 causes p53-dependent apoptosis of mouse pluripotent epiblast cells.

Disruption of mouse Prep1, which codes for a homeodomain transcription factor, leads to embryonic lethality during post-implantation stages. Prep1(-/-) embryos stop developing after implantation and before anterior visceral endoderm (AVE) formation. In Prep1(-/-) embryos at E6.5 (onset of gastrulation), the AVE is absent and the proliferating extra-embryonic ectoderm and epiblast, marked by Bmp4 and Oct4, respectively, are reduced in size. At E.7.5, Prep1(-/-) embryos are small and very delayed, showing no evidence of primitive streak or of differentiated embryonic lineages. Bmp4 is expressed residually, while the reduced number of Oct4-positive cells is constant up to E8.5. At E6.5, Prep1(-/-) embryos retain a normal mitotic index but show a major increase in cleaved caspase 3 and TUNEL staining, indicating apoptosis. Therefore, the mouse embryo requires Prep1 when undergoing maximal expansion in cell number. Indeed, the phenotype is partially rescued in a p53(-/-), but not in a p16(-/-), background. Apoptosis is probably due to DNA damage as Atm downregulation exacerbates the phenotype. Despite this early lethal phenotype, Prep1 is not essential for ES cell establishment. A differential embryonic expression pattern underscores the unique function of Prep1 within the Meis-Prep family.

[Childhood-onset systemic lupus]. / Lupus systémique de l'enfant.

CHILDHOOD-ONSET SYSTEMIC LUPUS. Childhood-onset systemic lupus (SL) is a rare multifactorial autoimmune disease belonging to connectivitis. Clinical presentation is very heterogeneous with multi-systemic involvement: skin, joint, renal, hematological, neuropsychiatric, pulmonary, cardiac among others. Renal involvement is particularly frequent and severe in children and must be checked ou on a regular basis by screening for proteinuria. Lab exams show the production of antibodies directed against the native double-stranded DNA, excessive production of type I interferon, consumption of complement is observed during periods of flare-up. There are rare forms of monogenic SL which must be evocated in case of early-onset, familial cases or when occurring in boys.

LUPUS SYSTÉMIQUE DE L'ENFANT. Le lupus systémique (LS) de l'enfant est une maladie auto-immune multifactorielle rare appartenant aux connectivites. Sa présentation clinique est très hétérogène, avec des atteintes multisystémiques : cutanées, articulaires, rénales, hématologiques, neuropsychiatriques, pulmonaires, cardiaques, entre autres. L'atteinte rénale est particulièrement fréquente et sévère chez l'enfant et doit être dépistée régulièrement par la recherche de protéinurie. Biologiquement, le LS se caractérise par la production d'anticorps dirigés contre l'ADN natif double brin et une production excessive d'interféron de type I ; une consommation du complément est constatée lors des périodes de poussée. Il existe des formes rares de LS monogénique, qui doivent être évoquées devant le caractère précoce de la maladie ou chez le garçon.

Evaluation of Slowfade Diamond as a buffer for STORM microscopy.

We study the potential of the commercial mounting medium Slowfade diamond as a buffer for STORM microscopy. We show that although it does not work with the popular far-red dyes typically used for STORM imaging, such as Alexa Fluor 647, it performs really well with a wide variety of green-excited dyes such as Alexa Fluor 532, Alexa Fluor 555 or CF 568. Moreover, imaging can be performed several months after the samples are mounted in this environment and kept in the fridge, providing a convenient way to preserve samples for STORM imaging, as well as to keep calibration samples, for example for metrology or teaching in particular in imaging facilities.

Cryopreservation effect on DNA methylation profile in rainbow trout spermatozoa.

Spermatozoa are the cells that are most commonly used for cryopreservation of valuable genetic resources in aquaculture. It is known that fish spermatozoa transmit to the embryo not only their genetic but also their epigenetic profile, especially DNA methylation. Therefore, any alteration of the DNA methylation profile in spermatozoa induces the risk of transmitting epigenetic alterations to the offspring. The aim of this study was to assess the effect of cryopreservation on DNA methylation in rainbow trout spermatozoa. To trigger variable cellular response after freezing-thawing, spermatozoa from mature males were cryopreserved with dimethyl sulfoxide, methanol or glycerol as cryoprotectant. We observed that dimethyl sulfoxide was the best to preserve thawed spermatozoa functions. Methanol only slightly preserved all the cellular parameters, while glycerol failed to protect motility and fertilization ability. The consequences on DNA methylation were assessed using Reduced Representation Bisulfite Sequencing (RRBS). Sperm cryopreservation did not thoroughly impact DNA methylation, although 335-564 differentially methylated cytosines were characterized depending on the cryoprotectant. Very few of them were shared between cryoprotectants, and no correlation with the extent of cellular damage was found. Our study showed that DNA methylation was only slightly altered after sperm cryopreservation, and this may render further analysis of the risk for the progeny very challenging.

Spermatozoa methylome and its sensitivity to water temperature in a teleost fish.

Global climate change and heat waves are sources of stress which fish are facing in the wild as well as in aquaculture context. In coping with important environmental variations, they demonstrate a great plasticity and a tendency for acclimation throughout generations. Here, we question whether fish might be prone to transmit epigenetic alterations through their gametes to their offspring, thus driving rapid environmental adaptation. The question of epigenetic inheritance in fish has become of crucial interest in the recent years, when the mammalian model of methylome erasure in germ cells and embryos was found not to be conserved. In this work, by sequencing spermatozoa after bisulfite conversion, we characterized the methylation landscape of the paternal gamete in rainbow trout (in comparison to muscle) before to demonstrate its sensitivity to a 4 °C increased rearing temperature during spermatogenesis. We found that spermatozoa methylome specifically primes housekeeping and developmental genes for activation and might be instrumental to early development. Most of these methylation-free promoters were not affected by temperature, attesting the robustness of the epigenetic programming of early development. However, the increase of temperature triggered the differential methylation of 5359 regions, among which 560 gene promoters control spermiogenesis and lipid metabolism. We therefore report, for the first time in fish, that sperm epigenetic landscape carries marks of parental thermal living conditions, suggesting that DNA methylation might be a molecular basis of intergenerational inheritance.