The C. elegans SET1 histone methyltransferase SET-2 is not required for transgenerational memory of silencing.

The SET-2 /SET1 histone H3K4 methyltransferase and RNAi pathway components are required to maintain fertility across generations in C. elegans . SET-2 preserves the germline transcriptional program transgenerationally, and RNAi pathways rely on small RNAs to establish and maintain transgenerational gene silencing. We investigated whether the functionality of RNAi-induced transgenerational silencing and the composition of pools of endogenous small RNA are affected by the absence of SET-2 . Our results suggest that defects in RNAi pathways are not responsible for the transcriptional misregulation observed in the absence of SET-2 .

SIN-3 acts in distinct complexes to regulate the germline transcriptional program in Caenorhabditis elegans.

The transcriptional co-regulator SIN3 influences gene expression through multiple interactions that include histone deacetylases. Haploinsufficiency and mutations in SIN3 are the underlying cause of Witteveen-Kolk syndrome and related intellectual disability and autism syndromes, emphasizing its key role in development. However, little is known about the diversity of its interactions and functions in developmental processes. Here, we show that loss of SIN-3, the single SIN3 homolog in Caenorhabditis elegans, results in maternal-effect sterility associated with de-regulation of the germline transcriptome, including de-silencing of X-linked genes. We identify at least two distinct SIN3 complexes containing specific histone deacetylases and show that they differentially contribute to fertility. Single-cell, single-molecule fluorescence in situ hybridization reveals that in sin-3 mutants the X chromosome becomes re-expressed prematurely and in a stochastic manner in individual germ cells, suggesting a role for SIN-3 in its silencing. Furthermore, we identify histone residues whose acetylation increases in the absence of SIN-3. Together, this work provides a powerful framework for the in vivo study of SIN3 and associated proteins.

Management of rare inherited bleeding disorders: Proposals of the French Reference Centre on Haemophilia and Rare Coagulation Disorders.

INTRODUCTION: The rare coagulation disorders may present significant difficulties in diagnosis and management. In addition, considerable inter-individual variation in bleeding phenotype is observed amongst affected individuals, making the bleeding risk difficult to assess in affected individuals. The last international recommendations on rare inherited bleeding disorders (RIBDs) were published by the United Kingdom Haemophilia Centre Doctors' Organisation in 2014. Since then, new drugs have been marketed, news studies on surgery management in patients with RIBD have been published, and new orphan diseases have been described. AIM: Therefore, the two main objectives of this review, based on the recent recommendations published by the French Reference Centre on Haemophilia and Rare Bleeding Disorders, are: (i) to briefly describe RIBD (clinical presentation and diagnostic work-up) to help physicians in patient screening for the early detection of such disorders; and (ii) to focus on the current management of acute haemorrhages and long term prophylaxis, surgical interventions, and pregnancy/delivery in patients with RIBD.

Assessment of the clinical perception, quality of life and satisfaction of patients with severe congenital haemophilia A without inhibitor after 1 year of emicizumab therapy.

INTRODUCTION: Since the approval by the EMA of emicizumab for the care of severe haemophilia A without inhibitor, most of the patients of our haemophilia treatment centre started this new treatment. Thanks to the setting of a therapeutic patient education program including three pharmaceutical consultations (PC), we could follow patients' lifestyle evolution. AIM: The study aimed to assess the perceived clinical evolution, quality of life and treatment satisfaction of patients after 1 year of emicizumab therapy in real-life settings. METHODS: The study was observational, retrospective and monocentric. Every patient over 18 years old receiving emicizumab from June 2020 and who underwent the 3 PC until March 2022 were included. The clinical evolution was self-estimated by patients with zero-to-six scales before versus 1 year after emicizumab, according to the following parameters: general health state, pain and bleedings (spontaneous or post-traumatic, and patients' identification ability). Patients' quality of life was also estimated with the EQ-5D-3L survey. Their satisfaction, graduated with a zero-to-ten scale, and treatment management were reported during the third PC. RESULTS: Thirty-eight patients were enrolled. Their general health state improved significantly (p = .0023) with an EQ-5D-3L score at 69.6 (±19.4) out of 100. Although chronic pains remained a persistent issue for 33 (86.8%) patients, their intensity was significantly decreasing after 1 year. Perceived frequency of bleedings was significantly reduced too. On average, the satisfaction of emicizumab therapy was 9.1 (± 1.02) out of 10. CONCLUSION: After 1 year of emicizumab therapy, the general health state estimated by patients improved, the pain and the perceived frequency of bleedings diminished. Overall, this treatment received a high patients' satisfaction rate.

A case of Epstein-Barr virus-associated smooth muscle tumor of the posterior interosseous nerve mimicking schwannoma.

Here we report a case of Epstein-Barr virus (EBV)-associated smooth muscle tumor (SMT) of the peripheral nerve in a young man seropositive for human immunodeficiency virus (HIV). Initially, the lesion was clinically and radiologically confused with a schwannoma of the forearm's posterior interosseous nerve. The diagnosis was corrected by histological examination, which revealed a well-defined tumor consisting of eosinophilic spindle cells, positive for α-smooth muscle actin on immunohistochemistry and positive for EBV-encoded early RNA (EBER) on in situ hybridization. EBV-associated SMTs are well described in the literature; they are frequently multiple and arise in many organs. They occur preferentially in young adults with poorly controlled and chronic HIV infection. The prognosis is influenced by the complications of immunodeficiency. To our knowledge, this is the first description of a peripheral nerve location. Because EBV-associated SMT should be considered in the differential diagnosis of a tumor in the peripheral or central nervous systems in immunocompromised patients, EBV should be tested in these locations. Thus, a cause of immunodeficiency should be identified when the diagnosis of EBV-associated SMT is made.

The Hemarthrosis-Simulating Knee Model: A Useful Tool for Individualized Education in Patients with Hemophilia (GEFACET Study).

BACKGROUND: Hemophilic arthropathy is a major complication in patients with severe hemophilia. A plastic knee model has been developed for the therapeutic education of patients to promote improved care management and self-treatment skills. The objective of this study was to evaluate the impact of this hemarthrosis-simulating artificial knee (HSAK) on patients' knowledge of their disease and its treatment. METHODS: In this observational study, the impact of HSAK was assessed during individualized education in patients with severe/moderately severe hemophilia A or B at seven hemophilia treatment centers in France. Participants provided written informed consent and completed questionnaires to assess knowledge of their disease (score range: 0-7) and knowledge of their treatment (score range: 0-4). Questionnaires were completed before, immediately after and 6 months after HSAK use. The scores obtained before and after the use of the HSAK were compared. RESULTS: The participants comprised 32 children, 29 teenagers, and 31 adults. The mean (SD) disease knowledge score increased significantly in all age groups of patients from 4.5 (2.0) to 5.9 (1.5; p<0.001) immediately after the training and remained unchanged at 6 months. Mean (SD) treatment knowledge scores were unchanged, but Wilcoxon signed rank testing showed a significant increase after the training course that was maintained at 6 months in children and teenagers. CONCLUSION: These findings suggest that an individualized training course can enhance the understanding of hemophilia in patients of all ages, especially in children and teenagers, and that the HSAK may assist in improving patients' management of their disease.

Pharmacodynamics of eftrenonacog-alfa (rFIX-Fc) in severe hemophilia B patients: A real-life study.

Eftrenonacog-alfa is a recombinant factor IX-Fc fusion protein increasingly prescribed in hemophilia B patients. We aimed to assess its pharmacodynamics (PD) in real-life setting via FIX activity measurement and thrombin generation assay (TGA). Sixty samples from 15 severe hemophilia B treated patients were collected at different time points. FIX activity was measured using product-specific one-stage clotting assay (reference method) and two chromogenic assays (CSA) (Biophen FIX and Rox FIX). TGA was triggered with 1 pM tissue factor. Five parameters were analyzed: lag time (LT), time to peak (TTP), peak height (PH), endogenous thrombin potential (ETP), and velocity. PD models were built to characterize their relationships with FIX activity, using mixed effects models. Mean trough FIX level was estimated at 4.64 (±1.50) IU/dl with a recovery at 0.78 (±0.16) IU/dl per 1 IU/kg injected dose. FIX activity ranged between 1 and 86 IU/dl with 21.5 IU/dl median value. Biophen FIX and Rox FIX allowed reliable measurements except in samples with FIX <20 IU/dl in which values were underestimated (delta >30%). PD models revealed that velocity was the most sensitive TGA parameter to FIX activity followed by PH, ETP, TTP and finally LT. Following FIX activity peak after eftrenonacog-alfa injection, velocity decreased first, followed by PH then ETP. Both CSA failed to accurately measure FIX in severe hemophilia B patients receiving eftrenonacog-alfa throughout the measuring range. TGA could be an additional valuable tool to evaluate hemostasis balance in treated patients.

Caenorhabditis elegans SET1/COMPASS Maintains Germline Identity by Preventing Transcriptional Deregulation Across Generations.

Chromatin regulators contribute to the maintenance of the germline transcriptional program. In the absence of SET-2, the Caenorhabditis elegans homolog of the SET1/COMPASS H3 Lys4 (H3K4) methyltransferase, animals show transgenerational loss of germline identity, leading to sterility. To identify transcriptional signatures associated with progressive loss of fertility, we performed expression profiling of set-2 mutant germlines across generations. We identify a subset of genes whose misexpression is first observed in early generations, a step we refer to as priming; their misexpression then further progresses in late generations, as animals reach sterility. Analysis of misregulated genes shows that down-regulation of germline genes, expression of somatic transcriptional programs, and desilencing of the X-chromosome are concurrent events leading to loss of germline identity in both early and late generations. Upregulation of transcription factor LIN-15B, the C/EBP homolog CEBP-1, and TGF-ß pathway components strongly contribute to loss of fertility, and RNAi inactivation of cebp-1 and TGF-ß/Smad signaling delays the onset of sterility, showing they individually contribute to maintenance of germ cell identity. Our approach therefore identifies genes and pathways whose misexpression actively contributes to the loss of germ cell fate. More generally, our data shows how loss of a chromatin regulator in one generation leads to transcriptional changes that are amplified over subsequent generations, ultimately leading to loss of appropriate cell fate.

A Role for Caenorhabditis elegans COMPASS in Germline Chromatin Organization.

Deposition of histone H3 lysine 4 (H3K4) methylation at promoters is catalyzed by the SET1/COMPASS complex and is associated with context-dependent effects on gene expression and local changes in chromatin organization. The role of SET1/COMPASS in shaping chromosome architecture has not been investigated. Here we used Caenorhabditis elegans to address this question through a live imaging approach and genetic analysis. Using quantitative FRET (Förster resonance energy transfer)-based fluorescence lifetime imaging microscopy (FLIM) on germ cells expressing histones eGFP-H2B and mCherry-H2B, we find that SET1/COMPASS influences meiotic chromosome organization, with marked effects on the close proximity between nucleosomes. We further show that inactivation of set-2, encoding the C. elegans SET1 homologue, or CFP-1, encoding the chromatin targeting subunit of COMPASS, enhances germline chromosome organization defects and sterility of condensin-II depleted animals. set-2 loss also aggravates germline defects resulting from conditional inactivation of topoisomerase II, another structural component of chromosomes. Expression profiling of set-2 mutant germlines revealed only minor transcriptional changes, suggesting that the observed effects are at least partly independent of transcription. Altogether, our results are consistent with a role for SET1/COMPASS in shaping meiotic chromosomes in C. elegans, together with the non-histone proteins condensin-II and topoisomerase. Given the high degree of conservation, our findings expand the range of functions attributed to COMPASS and suggest a broader role in genome organization in different species.

Repression of somatic cell fate in the germline.

Germ cells must transmit genetic information across generations, and produce gametes while also maintaining the potential to form all cell types after fertilization. Preventing the activation of somatic programs is, therefore, crucial to the maintenance of germ cell identity. Studies in Caenorhabditis elegans, Drosophila melanogaster, and mouse have revealed both similarities and differences in how somatic gene expression is repressed in germ cells, thereby preventing their conversion into somatic tissues. This review will focus on recent developments in our understanding of how global or gene-specific transcriptional repression, chromatin regulation, and translational repression operate in the germline to maintain germ cell identity and repress somatic differentiation programs.

Prevention and treatment of atherosclerosis in haemophilia - how to balance risk of bleeding with risk of ischaemic events.

Life expectancy for patients with haemophilia (PWH) has significantly increased in the last decades, due to improvement of clotting factor replacement therapy. However, despite a lower cardiovascular mortality rate and contrasting prevalence for non-fatal ischaemic heart disease (IHD), cardiovascular diseases are increasing in PWH. The prevalence of cardiovascular risk factors in PWH is as prevalent as in the general population, whereas an increased risk of hypertension has been observed in some studies. Furthermore, PWH are not protected against atherosclerosis. Coronary artery disease treatment is extremely challenging in PWH. Two 'institutional' guidelines for the management of IHD in PWH have been published. Since these recommendations, the use of new drugs such as prasugrel, ticagrelor, bivalirudin, new oral anticoagulants and new drug-eluting stents have been recommended in the general population but should be evaluated in PWH. Some questions arise: which trough level during long-term single or dual antiplatelet treatment (DAT) is really needed? The clinical role of platelet testing remains ill defined but may be considered in selected patients. A multidisciplinary approach is necessary for the management of IHD in PWH in order to treat the patient as any patient according to the cardiological guidelines during the acute phase, and long-term management should be discussed.

The SET-2/SET1 histone H3K4 methyltransferase maintains pluripotency in the Caenorhabditis elegans germline.

Histone H3 Lys 4 methylation (H3K4me) is deposited by the conserved SET1/MLL methyltransferases acting in multiprotein complexes, including Ash2 and Wdr5. Although individual subunits contribute to complex activity, how they influence gene expression in specific tissues remains largely unknown. In Caenorhabditis elegans, SET-2/SET1, WDR-5.1, and ASH-2 are differentially required for germline H3K4 methylation. Using expression profiling on germlines from animals lacking set-2, ash-2, or wdr-5.1, we show that these subunits play unique as well as redundant functions in order to promote expression of germline genes and repress somatic genes. Furthermore, we show that in set-2- and wdr-5.1-deficient germlines, somatic gene misexpression is associated with conversion of germ cells into somatic cells and that nuclear RNAi acts in parallel with SET-2 and WDR-5.1 to maintain germline identity. These findings uncover a unique role for SET-2 and WDR-5.1 in preserving germline pluripotency and underline the complexity of the cellular network regulating this process.

Recombinant factor VIII products and inhibitor development in previously untreated boys with severe hemophilia A.

Six recombinant factor VIII (rFVIII) products have been marketed worldwide. In 2013, the Research of Determinants of Inhibitor Development (RODIN) study group reported an unexpectedly high risk of inhibitor development with a second-generation full-length rFVIII (Product D) in previously untreated patients (PUPs) with severe hemophilia A (HA). In 1994, French public health authorities established a prospective cohort to monitor hemophilia treatment safety. A PUP subgroup was designed to investigate inhibitor risk factors. We analyzed this subcohort in view of the RODIN findings. After excluding 50 patients who participated in the RODIN study, the primary analysis focused on 303 boys with severe HA first treated with a rFVIII product. A clinically significant inhibitor was detected in 114 boys (37.6%). The inhibitor incidence was higher with Product D vs the most widely used rFVIII product (adjusted hazard ratio [aHR], 1.55; 95% confidence interval [CI], 0.97-2.49). Similar results were found for high-titer inhibitors and in 10 sensitivity analyses. No heterogeneity was observed between RODIN and our results. Combined aHRs were 1.58 (95% CI, 1.17-2.14) for all inhibitors and 1.70 (95% CI, 1.15-2.52) for high-titer inhibitors. Our results confirm the higher immunogenicity of Product D vs other rFVIII products in PUPs with severe HA.

Transgenerational functions of small RNA pathways in controlling gene expression in C. elegans.

RNA silencing processes use exogenous or endogenous RNA molecules to specifically and robustly regulate gene expression. In C. elegans, initial mechanistic descriptions of the different silencing processes focused on posttranscriptional regulation. In this review, we discuss recent work showing that, in this model organism, RNA silencing also controls the transcription of target genes by inducing heterochromatin formation. Specifically, it has been shown that ribonucleoprotein complexes containing small RNAs, either processed from exogenous dsRNA or synthesized from the genome itself, and proteins of the Argonaute family, mediate the deposition of repressive histone marks at the targeted loci. Interestingly, the accumulation of repressive marks is required for the inheritance of the silencing effect and the establishment of an epigenetic memory that discriminates self- from non-self-RNAs.

Biosynthesis of ionotropic acetylcholine receptors requires the evolutionarily conserved ER membrane complex.

The number of nicotinic acetylcholine receptors (AChRs) present in the plasma membrane of muscle and neuronal cells is limited by the assembly of individual subunits into mature pentameric receptors. This process is usually inefficient, and a large number of the synthesized subunits are degraded by endoplasmic reticulum (ER)-associated degradation. To identify cellular factors required for the synthesis of AChRs, we performed a genetic screen in the nematode Caenorhabditis elegans for mutants with decreased sensitivity to the cholinergic agonist levamisole. We isolated a partial loss-of-function allele of ER membrane protein complex-6 (emc-6), a previously uncharacterized gene in C. elegans. emc-6 encodes an evolutionarily conserved 111-aa protein with two predicted transmembrane domains. EMC-6 is ubiquitously expressed and localizes to the ER. Partial inhibition of EMC-6 caused decreased expression of heteromeric levamisole-sensitive AChRs by destabilizing unassembled subunits in the ER. Inhibition of emc-6 also reduced the expression of homomeric nicotine-sensitive AChRs and GABAA receptors in C. elegans muscle cells. emc-6 is orthologous to the yeast and human EMC6 genes that code for a component of the recently identified ER membrane complex (EMC). Our data suggest this complex is required for protein folding and is connected to ER-associated degradation. We demonstrated that inactivation of additional EMC members in C. elegans also impaired AChR synthesis and induced the unfolded protein response. These results suggest that the EMC is a component of the ER folding machinery. AChRs might provide a valuable proxy to decipher the function of the EMC further.

Engineering the Caenorhabditis elegans genome by Mos1-induced transgene-instructed gene conversion.

Mos1-induced transgene-instructed gene conversion (MosTIC) is a technique of choice to engineer the genome of the nematode Caenorhabditis elegans. MosTIC is initiated by the excision of Mos1, a DNA transposon of the Tc1/Mariner super family that can be mobilized in the germ line of C. elegans. Mos1 excision creates a DNA double-strand break that is repaired by several cellular mechanisms, including transgene-instructed gene conversion. For MosTIC, the transgenic repair template used by the gene conversion machinery is made of sequences that share DNA homologies with the genomic region to engineer and carries the modifications to be introduced in the genome. In this chapter, we present two MosTIC protocols routinely used.

Genome engineering by transgene-instructed gene conversion in C. elegans.

The nematode Caenorhabditis elegans is an anatomically simple metazoan that has been used over the last 40 years to address an extremely wide range of biological questions. One major advantage of the C. elegans system is the possibility to conduct large-scale genetic screens on randomly mutagenized animals, either looking for a phenotype of interest and subsequently relate the mutated gene to the biological process under study ("forward genetics"), or screening for molecular lesions impairing the function of a specific gene and later analyze the phenotype of the mutant ("reverse genetics"). However, the nature of the genomic lesion is not controlled in either strategy. Here we describe a technique to engineer customized mutations in the C. elegans genome by homologous recombination. This technique, called MosTIC (for Mos1 excision induced transgene-instructed gene conversion), requires a C. elegans strain containing an insertion of the Drosophila transposon Mos1 within the locus to modify. Expression of the Mos transposase in the germ line triggers Mos1 excision, which causes a DNA double strand break (DSB) in the chromosome at the excision site. The DSB locally stimulates DNA repair by homologous recombination, which can sometimes occur between the chromosome and a transgene containing sequence homologous to the broken locus. In that case, sequence variations contained in the repair template will be copied by gene conversion into the genome. Here we provide a detailed protocol of the MosTIC technique, which can be used to introduce point mutations and generate knockout and knock-in alleles.

Caenorhabditis elegans chromatin-associated proteins SET-2 and ASH-2 are differentially required for histone H3 Lys 4 methylation in embryos and adult germ cells.

Methylation of histone H3 lysine 4 (H3K4me), a mark associated with gene activation, is mediated by SET1 and the related mixed lineage leukemia (MLL) histone methyltransferases (HMTs) across species. Mammals contain seven H3K4 HMTs, Set1A, Set1B, and MLL1-MLL5. The activity of SET1 and MLL proteins relies on protein-protein interactions within large multisubunit complexes that include three core components: RbBP5, Ash2L, and WDR5. It remains unclear how the composition and specificity of these complexes varies between cell types and during development. Caenorhabditis elegans contains one SET1 protein, SET-2, one MLL-like protein, SET-16, and single homologs of RbBP5, Ash2L, and WDR5. Here we show that SET-2 is responsible for the majority of bulk H3K4 methylation at all developmental stages. However, SET-2 and absent, small, or homeotic discs 2 (ASH-2) are differentially required for tri- and dimethylation of H3K4 (H3K4me3 and -me2) in embryos and adult germ cells. In embryos, whereas efficient H3K4me3 requires both SET-2 and ASH-2, H3K4me2 relies mostly on ASH-2. In adult germ cells by contrast, SET-2 serves a major role whereas ASH-2 is dispensable for H3K4me3 and most H3K4me2. Loss of SET-2 results in progressive sterility over several generations, suggesting an important function in the maintenance of a functional germ line. This study demonstrates that individual subunits of SET1-related complexes can show tissue specificity and developmental regulation and establishes C. elegans as a model to study SET1-related complexes in a multicellular organism.

Manipulating the Caenorhabditis elegans genome using mariner transposons.

Tc1, one of the founding members of the Tc1/mariner transposon superfamily, was identified in the nematode Caenorhabditis elegans more than 25 years ago. Over the years, Tc1 and other endogenous mariner transposons became valuable tools for mutagenesis and targeted gene inactivation in C. elegans. However, transposition is naturally repressed in the C. elegans germline by an RNAi-like mechanism, necessitating the use of mutant strains in which transposition was globally derepressed, which causes drawbacks such as uncontrolled proliferation of the transposons in the genome and accumulation of background mutations. The more recent mobilization of the Drosophila mariner transposon Mos1 in the C. elegans germline circumvented the problems inherent to endogenous transposons. Mos1 transposition strictly depends on the expression of the Mos transposase, which can be controlled in the germline using inducible promoters. First, Mos1 can be used for insertional mutagenesis. The mobilization of Mos1 copies present on an extrachromosomal array results in the generation of a small number of Mos1 genomic insertions that can be rapidly cloned by inverse PCR. Second, Mos1 insertions can be used for genome engineering. Triggering the excision of a genomic Mos1 insertion causes a chromosomal break, which can be repaired by transgene-instructed gene conversion. This process is used to introduce specific changes in a given gene, such as point mutations, deletions or insertions of a tag, and to create single-copy transgenes.

Mos1 transposition as a tool to engineer the Caenorhabditis elegans genome by homologous recombination.

Gene knockouts and knock-ins have emerged as powerful tools to study gene function in model organisms. The construction of such engineered alleles requires that homologous recombination between a transgenic fragment carrying the modifications desired in the genome and the locus to engineer occurs at high frequencies. Homologous recombination frequency is significantly increased in the vicinity of a DNA double-strand break. Based on this observation, a new generation of transgene-instructed genome engineering protocols was developed. Here, we present MosTIC (for "Mos1 excision-induced transgene-instructed gene conversion"), a new technique that provides a means to engineer the Caenorhabditis elegans genome. MosTIC is initiated by the mobilization of Mos1, a Drosophila transposon experimentally introduced in C. elegans. During MosTIC, a Mos1 insertion localized in the genomic region to engineer is mobilized after germline expression of the Mos transposase. Mos1 excision generates a DNA double-strand break, which is repaired by homologous recombination using a transgenic repair template. This results in the transfer of information from the transgene into the genome. Depending on the method used to trigger Mos1 excision, two alternative MosTIC protocols are available, which are presented here in detail. This technique can be used for a wide range of applications, such as structure-function analysis, protein localization and purification, genetic screens or generation of single copy transgenes at a defined locus in the genome.